A 1225 m long, 35 m high zone earth filled embankment was being constructed from 1981 to 1984 from a British Regional Water Authority to regulate flows in the River Derwent in England. The Carsington Dam was planned to be one of the largest earth filled dams in Britain. Its reservoir capacity was 35 million m3 and the watertight element was Rolled Clay Core with an upstream extension of boot shaped and shoulders of compacted mudstone with horizontal drainage layers of crushed limestone about 4 metres apart and a cut-off grout curtain (Davey and Eccles, 1983).
The downstream slope was 1:2.5 and the upstream slope 1:3. Fill placing began in May 1982 and took three summers, with winter shutdowns. In August 1983 a small berm was placed at the upstream toe to compensate for a faster rate of construction. Earth filling restarted in April 1984 and was one metre below the final crest level on 4 June 1984 when the upstream slope slipped (Skempton, 1985). Observations of pore pressure and settlement were made during construction at four sections and horizontal displacements were observed from August 1983. The Carsington Dam was almost completed on 1984.
However, at the beginning of June 1984, a 400-m length of the upstream shoulder of the embankment dam slipped some 11 m and failed. At the time of the failure, embankment construction was virtually complete with the dam approaching its maximum height of 35 m. Horizontal drainage blankets were incorporated in both the upstream and the downstream shale fill shoulders. Piezometers had been installed and pore pressures were being monitored in the foundation, in the clay core, and in the shoulder fill. The failure surface passed through the boot shaped rolled clay core and a relatively thin layer of surface clay in the foundation of the dam. Investigation of the events at Carsington has made important contributions to the fundamental understanding of the behaviour of large earthworks of this type (Vaughan et al., 1989; Dounias et al., 1996).
The objective of this research is to evaluate a detailed slope stability assessment of the Carsington Earth Embankment Dam in the UK used to retain mine tailings.
By using and applying advanced geotechnical engineering analysis tools and modelling techniques the Carsington Earth Embankment Dam, which is considered a particular geotechnical structure, is analysed.
In the current detailed slope stability analyses the total and effective stress state soil properties / parameters were used, and the most critical slip circle centre according to Fellenius - Jumikis method was initially determined. Subsequently, the Carsington Earth Embankment Dam and its foundation was analysed and examined against failure by slope instability. Considerations of loading conditions which may result to instability for all likely combinations of reservoir and tailwater levels, seepage conditions, both after and during construction were made, and hence three construction and / or loading condit
Designing a Concrete Beam Using the New AS3600:2018 - Webinar Slides - ClearC...ClearCalcs
The 2018 revision of the AS3600 Concrete standard includes major revisions for areas including phi factors, shear, deflection, rectangular stress block, and shrinkage/creep.
In this webinar, ClearCalcs lead engineering developer Brooks Smith discusses some of these key changes, and runs through the design process for a concrete beam design before demonstrating a few worked examples using AS3600:2018 in the newly released rectangular concrete beam calculator on ClearCalcs.com.
Watch the recorded webinar: https://vimeo.com/295532300
Explore all of our concrete, timber, and steel calculations at clearcalcs.com.
Earthquake Load Calculation (base shear method)
The 3-story standard office building is located in Los Angeles situated on stiff soil. The
structure of the building is steel special moment frame. All moment-resisting frames are
located at the perimeter of the building. Determine the earthquake force on each story in
North-South direction.
Timber Design to AS1720.1 (+Amdt 3, 2010) Webinar - ClearCalcsClearCalcs
Understanding the complete timber design process and the
key differences with wood design using AS 1720.1 or AS 1684.
ClearCalcs engineering development lead Brooks Smith gave this free engineering webinar covering Timber Design to AS1720.1, including a discussion of common design parameters and considerations, a comparison with the residentially geared AS1720.3 and AS1684, as well as worked examples using the AS 1720.1 calculator in ClearCalcs.
Long a mainstay in residential construction due to its versatility, cost, and environmental friendliness, timber is now seeing growing demand in mid rise structures thanks to growing understanding of how to utilise the material, as well as the continued rise in availability of engineered wood products (EWP) such as glue laminated and cross laminated timbers.
However, unlike steel whose properties tend to remain fairly constant over time, timber has a range of factors that need to be considered by engineers including moisture content, creep, and load duration factors.
Designing a Concrete Beam Using the New AS3600:2018 - Webinar Slides - ClearC...ClearCalcs
The 2018 revision of the AS3600 Concrete standard includes major revisions for areas including phi factors, shear, deflection, rectangular stress block, and shrinkage/creep.
In this webinar, ClearCalcs lead engineering developer Brooks Smith discusses some of these key changes, and runs through the design process for a concrete beam design before demonstrating a few worked examples using AS3600:2018 in the newly released rectangular concrete beam calculator on ClearCalcs.com.
Watch the recorded webinar: https://vimeo.com/295532300
Explore all of our concrete, timber, and steel calculations at clearcalcs.com.
Earthquake Load Calculation (base shear method)
The 3-story standard office building is located in Los Angeles situated on stiff soil. The
structure of the building is steel special moment frame. All moment-resisting frames are
located at the perimeter of the building. Determine the earthquake force on each story in
North-South direction.
Timber Design to AS1720.1 (+Amdt 3, 2010) Webinar - ClearCalcsClearCalcs
Understanding the complete timber design process and the
key differences with wood design using AS 1720.1 or AS 1684.
ClearCalcs engineering development lead Brooks Smith gave this free engineering webinar covering Timber Design to AS1720.1, including a discussion of common design parameters and considerations, a comparison with the residentially geared AS1720.3 and AS1684, as well as worked examples using the AS 1720.1 calculator in ClearCalcs.
Long a mainstay in residential construction due to its versatility, cost, and environmental friendliness, timber is now seeing growing demand in mid rise structures thanks to growing understanding of how to utilise the material, as well as the continued rise in availability of engineered wood products (EWP) such as glue laminated and cross laminated timbers.
However, unlike steel whose properties tend to remain fairly constant over time, timber has a range of factors that need to be considered by engineers including moisture content, creep, and load duration factors.
Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.
Lecture 11 Shear Strength of Soil CE240Wajahat Ullah
Shear Strength of Soil
Shear strength in soils
Introduction
Definitions
Mohr-Coulomb criterion
Introduction
Lab tests for getting the shear strength
Direct shear test
Introduction
Procedure & calculation
Critical void ratio
Prepared by madam rafia firdous. She is a lecturer and instructor in subject of Plain and Reinforcement concrete at University of South Asia LAHORE,PAKISTAN.
Lecture 11 Shear Strength of Soil CE240Wajahat Ullah
Shear Strength of Soil
Shear strength in soils
Introduction
Definitions
Mohr-Coulomb criterion
Introduction
Lab tests for getting the shear strength
Direct shear test
Introduction
Procedure & calculation
Critical void ratio
Hydraulic failures .... 40%
Seepage failures…….. 30%
Structural failures .... 30%
(1) Overtopping
(2) Erosion of u/s slope by waves
(3) Erosion of d/s slope by wind and rain
(4) Erosion of d/s toe
(5) Frost action
(1) Overtopping = the design flood is under estimated.
spillway capacity is not adequet
spillway gates are not properly operated
free board is not sufficient
excessive settlement of the foundation and dam
(2) Erosion of u/s slope by waves = The waves developed near the top water surface due to the winds, try to notch out the soil from the upstream face and may even, sometimes, cause the slip of the upstream slope.
Upstream stone pitching or riprap should, therefore, be provided to avoid such failures.
(3) Erosion of d/s slope by wind and rain = The rainwater flowing down the slope; may result in the formation of 'gullies' on the downstream slope thus damaging the dam which may generally lead to partial failure of the dam or in some cases it may cause complete failure of the dam.
Erosion of d/s toe : = Toe erosion may occur due to two reasons :
erosion due to tail water
erosion due to cross currents that may come from spillway buckets.
Frost action : = If the earth dam is located at a place where the temperature falls below the freezing point, frost may form in the pores of the soil in the earth dam.
When there is heaving, the cracks may form in the soil. This may lead to dangerous seepage and consequent failure.
Seepage failures : = Seepage failures may occur due to the following causes :
(1) Piping through the foundation
(2) Piping through the dam
(3) Sloughing of d/s toe
Structural failures :=
Structural failures in earth dams are generally shear failures leading to sliding of the tents or the foundations.
(1) u/s and d/s slope failures due to construction pore pressures
(2) u/s slope failure due to sudden drawdown
(3) D/s slope failure due to steady seepage
(4) Foundation slide due to spontaneous liquefaction
(5) Failure due to earthquake
(6) Failure by spreading
(7) Slope protection failures
(8) Failure due to damage caused by borrowing animals
(9) Failure due to holes caused by leaching of water soluable salts
Criteria for safe Design of Earth Dam :
Section of an Earth Dam :
The design of an earth dam essentially consists of determining such a cross section
the dam which when constructed with the available materials will fulfill its required
tion with adequate safety. Thus there are two aspects of the design of an earth dam.
DAMS
Types of dams
Selection of dam sites
Geological characters for investigation
Selection of the dam type
Gravity dams
butress dams
embankment dams
arch dams
cupola dams
composite dams
Bhakra Dam
Mir Alam multi-arch dam
Idukki Dam
Tehri Dam
Ujani Dam or bhima dam
Brazil's Mining Tragedy : Lessons for the Mining IndustryPRABHASH GOKARN
The Brazilian mining tragedy was an eye-opener for the mining fraternity to introspect on the existing tailing management processes, identify gaps, complete hazard identification and risk assessments, and modify or develop safe operating procedures and emergency preparedness plans in line with the guidelines issued by Statutory Authorities from time to time. This is necessary to avert the occurrence of similar incidents in the future.
Ailments of the First Concrete Dam in Sri LankaNihal Vitharana
Nalanda dam is the oldest concrete gravity dam on the Island built in the 1950s by the Ceylon Department
of Irrigation. The dam was built in 9 monoliths having a dam crest length of approximately 125m and a
maximum height of about 36m. The spillway consists of: (1) a low-level uncontrolled ogee-crested horseshoe
section with a crest length of 46m, and (b) a high-level broad crested weir with a crest length of 43m.
It was designed and constructed according to the then standard practices adopted throughout the world.
Over the years, Nalanda dam has been showing signs of deterioration which is suspected to be Alkali-
Aggregate Reaction (AAR). The dam was also shown to be deficient with respect to the stability levels
required by modern standards. Under a program of dam safety improvement of the dams throughout Sri
Lanka, it was decided to stabilise Nalanda dam as the first step in addressing a series of issues affecting the
dam.
This paper presents the construction history, current issues, design assumptions and salient construction
features in the upgrading of the dam to modern dam safety requirements.
Back analysis of high tunnel convergences in clayey marlsSYSTRA
Ganntas Tunnel is part of the modernization project of the
railway between Alger and Oran, in Algeria. In order to double
and rectify the existing line between El Affroun and Khémis
Miliana, the alignment foresees the excavation of a 7km-long
twin tunnel. The excavation works started in June 2011 with
the contractor CCECC, under the supervision of SYSTRA.
Excavation is driven in conventional method by hydraulic
hammer simultaneously on 8 different faces since excavation
was started also from a junction window towards the middle
of the tunnel. The minimum longitudinal distance to be
respected between two contiguous tunnel faces has been set
to 30m. The tunnel cross-section is a 70m² oval shaped profile,
temporary support consists of shotcrete, bolts and steel ribs.
A 30 to 50cm thick cast in situ concrete final lining is provided
as well.
When the tunnel reached a fault zone in soft clayey marls,
extreme squeezing occurred, works were stopped, and reprofiling
operations were carried out along more than 100m
tunnel length. To date, works proceed at slow rate since high
convergences are still monitored and completion of works is
not expected before December 2016.
Written by SYSTRA tunnel experts : MISANO Edoardo, COUBRAY Jean-Louis,
ESPINOZA CARMONA Fabiola
THE USE OF AIRBORNE EM CONDUCTIVITY TO LOCATE CONTAMINANT FLOW PATHS AT THE S...Brett Johnson
Richard W. Hammack, Garret A. Veloski, James I. Sams III, and Jennifer S. Shogren
U.S. DOE, National Energy Technology Laboratory, Pittsburgh, PA
Abstract
In 1986, the State of California posted a fish consumption advisory for Clearlake, a large,
freshwater lake located 80 miles north of San Francisco, because of mercury contamination. The
abandoned Sulphur Bank Mercury Mine on the eastern shore of Clearlake is the suspected source of
the mercury. Herman Impoundment, the now flooded open pit of the Sulphur Bank Mercury Mine, is
separated from Clearlake by a dam composed of waste rock removed from the open pit. Hydrological
and geochemical studies indicated that water is flowing from the open pit through the waste rock
dam into Clearlake. However, an accurate map of flow pathways through the waste rock dam was
needed for planning groundwater flow intervention. Results from an airborne EM conductivity survey
flown over the mine site and adjacent areas suggest the probable flow paths taken by the highly
conductive Herman Impoundment water through the waste rock dam. The airborne data were then used
to target areas for ground-based EM conductivity surveys with a Geonics EM34-3XL instrument. The
higher-resolution results of the ground-based survey corroborated the findings of the airborne
survey. This information will allow groundwater-flow intervention efforts to be concentrated within
small areas of the waste rock
dam.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Seismic Hazard Assessment Software in Python by Prof. Dr. Costas SachpazisDr.Costas Sachpazis
This simple Python software is designed to assist Civil and Geotechnical Engineers in performing site-specific seismic hazard assessments. The program calculates the seismic response spectrum based on user-provided geotechnical and seismic parameters, generating a comprehensive technical report that includes the response spectrum data and figures. The analysis adheres to Eurocode 8 and the Greek Annex, ensuring compliance with international standards for earthquake-resistant design.
Structural Analysis and Design of Foundations: A Comprehensive Handbook for S...Dr.Costas Sachpazis
Structural Analysis and Design of Foundations: A Comprehensive Handbook for Students and Professionals.
Unlock the potential of foundation design with Dr. Costas Sachpazis’s enlightening handbook, a meticulously crafted guide poised to become an indispensable resource for both budding and seasoned civil engineers. This comprehensive manual illuminates the theoretical and practical aspects of structural analysis and design across various types of foundations and retaining walls.
Within these pages, Dr. Sachpazis distills complex engineering principles into digestible, step-by-step processes, enhanced by detailed diagrams, case studies, and real-world examples that bridge the gap between academic study and professional application. From soil mechanics and load calculations to innovative design techniques and sustainability considerations, this book covers a vast landscape of structural engineering.
Key Features:
• In-Depth Analysis and Design: Explore thorough explanations of both shallow and deep foundation designs, supported by case studies that demonstrate their practical implementations.
• Practical Guides: Benefit from detailed guides on site investigation, bearing capacity calculations, and settlement analysis, ensuring designs are both robust and reliable.
• Innovative Techniques: Discover the latest advancements in foundation technology and retaining wall design, preparing you for future trends in civil engineering.
• Educational Tools: Utilize this handbook as an educational tool, perfect for both classroom learning and professional development.
Whether you're a student eager to learn the fundamentals or a professional seeking to deepen your expertise, Dr. Sachpazis’s handbook is designed to support and inspire excellence in the field of structural engineering. Embrace this opportunity to enhance your skills and contribute to building safer, more efficient structures.
Sheet Pile Wall Design and Construction: A Practical Guide for Civil Engineer...Dr.Costas Sachpazis
Sheet Pile Wall Design and Construction: A Practical Guide for Civil Engineers. By Dr. Costas Sachpazis.
A Technical Report provides information on Geotechnical Exploration and testing procedures, analysis techniques, allowable criteria, design procedures, and construction consideration for the selection, design, and installation of sheet pile walls.
"Sheet Pile Wall Design and Construction: A Practical Guide for Civil Engineers" by Dr. Costas Sachpazis provides an in-depth look into the engineering, design, and construction of sheet pile walls. The book details geotechnical exploration, testing procedures, and analysis techniques essential for determining soil properties and stability under various conditions, including seismic activity. It also covers the impact of groundwater on wall design and offers methods for controlling it during construction. Practical considerations for confined space work and the use of emerging technologies in sheet pile construction are discussed. The guide serves as a comprehensive resource for civil engineers aiming to enhance their expertise in creating durable and effective sheet pile wall solutions for complex engineering projects.
Sachpazis Costas: Geotechnical Engineering: A student's Perspective IntroductionDr.Costas Sachpazis
Geotechnical Engineering: A Student's Perspective
By Dr. Costas Sachpazis.
Geotechnical engineering is a branch of civil engineering that focuses on the behavior of earth materials such as soil and rock. It is a crucial aspect of any construction project, as the properties of the ground can have a significant impact on the design and stability of structures. Geotechnical engineers work to understand the physical and mechanical properties of soil and rock, as well as how these materials interact with man-made structures.
Geotechnical engineering plays a crucial role in the field of civil engineering, as it deals with the behavior of earth materials and how they interact with structures. Understanding the properties of soil and rock beneath the surface is essential for designing safe and stable structures that can withstand various loads and environmental conditions. Without proper knowledge of geotechnical engineering, civil engineers would not be able to ensure the safety and longevity of their projects.
Sachpazis: Steel member fire resistance design to Eurocode 3 / Σαχπάζης: Σχεδ...Dr.Costas Sachpazis
Project: Steel Member Fire Resistance Design (EN1993) - In accordance with EN1993-1-2:2005 incorporating Corrigenda December 2005 and the recommended values.
Παράδειγμα Σχεδιασμού Πυράντοχης Αντοχής Μέλους από Χάλυβα (EN 1993), Σύμφωνα με το EN 1993-1-2:2005 που ενσωματώνει το Corrigenda Δεκεμβρίου 2005 και τις συνιστώμενες τιμές.
Sachpazis_Retaining Structures-Ground Anchors and Anchored Systems_C_Sachpazi...Dr.Costas Sachpazis
A retaining wall is a structure that is designed to hold back soil or other materials when there is a change in ground elevation. Retaining walls are commonly used in civil engineering to support soil and prevent erosion. They are typically constructed of various materials, including concrete, masonry, and timber.
Retaining walls are used in a variety of settings, including residential and commercial construction, roadways and highways, and landscaping projects. They are often used to create level areas for building or landscaping by holding back soil or other materials on sloping terrain.
The design of a retaining wall depends on several factors, including the type of soil, the height of the wall, and the slope of the ground. There are several types of retaining walls, including gravity walls, cantilever walls, sheet pile walls, and anchored walls. The type of wall used depends on the specific requirements of the project.
Overall, retaining walls are an important component of civil engineering projects and are used to support soil and prevent erosion. They require careful design and construction to ensure their stability and effectiveness.
Pile configuration optimization on the design of combined piled raft foundationsDr.Costas Sachpazis
By: Birhanu Asefa, Eleyas Assefa, Lysandros Pantelidis,Costas Sachpazis
This paper examines the impact of different pile configurations and geometric parameters on the bearing capacity and the settlement response of a combined pile–raft foundation system utilizing FLAC3D software. The configurations considered were: (1) uniform piles (denoted as CONF1), (2) shorter and longer piles uniformly distributed on the plan view of the raft (CONF2), (3) shorter piles at the center and longer piles at the edge of the raft (CONF3), and (4) longer piles at the center and shorter piles at the edge of the raft (CONF4). In the same framework, different pile diameters and raft stiffnesses were examined. The piles are considered to float in a cohesive–frictional soil mass, simulating the thick cohesive soil deposit found in Addis Abeba (Ethiopia). During simulation, a zero-thickness interface element was employed to incorporate the complex interaction between the soil elements and the structural elements. The analyses indicate that the configuration of piles has a considerable effect on both the bearing capacity and the settlement response of the foundation system. CONF1 and CONF3 improve the bearing capacity and exhibits a smaller average settlement than other configurations. However, CONF3 registers the highest differential settlement. On the other hand, the lowest differential settlement was achieved by the CONF4 configuration; the same configuration also gives ultimate load resistance comparable to those provided by either CONF1 or CONF3. The study also showed that applying zero-thickness interface elements to simulate the interaction between components of the foundation system is suitable for examining piled raft foundations problem.
Σαχπάζης Πλεονεκτήματα και Προκλήσεις της Αιολικής ΕνέργειαςDr.Costas Sachpazis
Σαχπάζης: Πλεονεκτήματα και Προκλήσεις της Αιολικής Ενέργειας.
Πλεονεκτήματα και Προκλήσεις της Αιολικής Ενέργειας
Από Κώστα Σαχπάζη, Πολιτικό Μηχανικό, καθηγητή Πολυτεχνικής Σχολής στην Γεωτεχνική Μηχανική
Η αιολική ενέργεια προσφέρει πολλά πλεονεκτήματα, κάτι που εξηγεί γιατί είναι μια από τις ταχύτερα αναπτυσσόμενες πηγές ενέργειας στον κόσμο. Οι ερευνητικές προσπάθειες αποσκοπούν στην αντιμετώπιση των προκλήσεων για μεγαλύτερη χρήση της αιολικής ενέργειας.
Καθώς είναι πιο καθαρή και φιλική προς το κλίμα, η Αιολική Ενέργεια χρησιμοποιείται ολοένα και περισσότερο για να καλύψει τις συνεχώς αυξανόμενες παγκόσμιες ενεργειακές απαιτήσεις. Στην Ελλάδα, υπάρχει ένα μεγάλο κενό μεταξύ των Αιολικών Πόρων και της πραγματικής παραγωγής ενέργειας, και είναι επιτακτική ανάγκη να επεκταθεί η ανάπτυξη της αιολικής ενέργειας, ιδιαίτερα στις ημέρες μας μετά από την Νέα Εποχή της Απολιγνιτοποίησης που έχουμε εισέλθει με βάση τις προσταγές και τους νόμους της Ευρωπαϊκής Ένωσης.
Ας δούμε όμως παρακάτω περισσότερα για τα οφέλη της αιολικής ενέργειας και μερικές από τις προκλήσεις που προσπαθεί να ξεπεράσει:
Πλεονεκτήματα της Αιολικής Ενέργειας
Sachpazis: Raft Foundation Analysis and Design for a two Storey House Project...Dr.Costas Sachpazis
Sachpazis: Raft Foundation Analysis and Design for a two Storey House Project
In accordance with BS8110: PART 1: 1997 and Code of Practice for Geotechnical design and the U.K. recommended values
Παράδειγμα ανάλυσης και σχεδίασης Ζευκτών (Trusses) σύμφωνα με τον Ευρωκώδικα EC3, του Δρ. Κώστα Σαχπάζη.
Truss Analysis and Design example to EC3, by Dr. Costas Sachpazis
Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
MATATAG CURRICULUM: ASSESSING THE READINESS OF ELEM. PUBLIC SCHOOL TEACHERS I...NelTorrente
In this research, it concludes that while the readiness of teachers in Caloocan City to implement the MATATAG Curriculum is generally positive, targeted efforts in professional development, resource distribution, support networks, and comprehensive preparation can address the existing gaps and ensure successful curriculum implementation.
Thinking of getting a dog? Be aware that breeds like Pit Bulls, Rottweilers, and German Shepherds can be loyal and dangerous. Proper training and socialization are crucial to preventing aggressive behaviors. Ensure safety by understanding their needs and always supervising interactions. Stay safe, and enjoy your furry friends!
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
Acetabularia Information For Class 9 .docxvaibhavrinwa19
Acetabularia acetabulum is a single-celled green alga that in its vegetative state is morphologically differentiated into a basal rhizoid and an axially elongated stalk, which bears whorls of branching hairs. The single diploid nucleus resides in the rhizoid.
Normal Labour/ Stages of Labour/ Mechanism of LabourWasim Ak
Normal labor is also termed spontaneous labor, defined as the natural physiological process through which the fetus, placenta, and membranes are expelled from the uterus through the birth canal at term (37 to 42 weeks
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
How to Build a Module in Odoo 17 Using the Scaffold MethodCeline George
Odoo provides an option for creating a module by using a single line command. By using this command the user can make a whole structure of a module. It is very easy for a beginner to make a module. There is no need to make each file manually. This slide will show how to create a module using the scaffold method.
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
Detailed Slope Stability Analysis and Assessment of the Original Carsington Earth Embankment Dam Failure in the UK
1. Detailed Slope Stability Analysis and
Assessment of the Original Carsington
Earth Embankment Dam Failure in the
UK
Dr. Costas I. Sachpazis
Civil & Geotechnical Engineer (BEng (Hons) Civil Eng. UK, Dipl. Geol,
M.Sc.Eng UK, Ph.D. NTUA (Ε.Μ.Π.), Post-Doc. UK, Gr.m.ICE).
Associate Professor, Lab of Soil Mechanics, Department of Environmental
Engineering, Geotechnical Engineering Division, Technological Educational
Institute of Western Macedonia. Killa 50100, Kozani, Greece.
Ph: (+30) 210-5238127; Fax: (+30) 210-5711461.
e-mail the author: costas@sachpazis.info
ABSTRACT
A 1225 m long, 35 m high zone earth filled embankment was being constructed from 1981 to 1984 from
a British Regional Water Authority to regulate flows in the River Derwent in England. The Carsington
Dam was planned to be one of the largest earth filled dams in Britain. Its reservoir capacity was 35
million m3 and the watertight element was Rolled Clay Core with an upstream extension of boot shaped
and shoulders of compacted mudstone with horizontal drainage layers of crushed limestone about 4
metres apart and a cut-off grout curtain (Davey and Eccles, 1983).
The downstream slope was 1:2.5 and the upstream slope 1:3. Fill placing began in May 1982 and took
three summers, with winter shutdowns. In August 1983 a small berm was placed at the upstream toe to
compensate for a faster rate of construction. Earth filling restarted in April 1984 and was one metre
below the final crest level on 4 June 1984 when the upstream slope slipped (Skempton, 1985).
Observations of pore pressure and settlement were made during construction at four sections and
horizontal displacements were observed from August 1983. The Carsington Dam was almost completed
on 1984.
However, at the beginning of June 1984, a 400-m length of the upstream shoulder of the embankment
dam slipped some 11 m and failed. At the time of the failure, embankment construction was virtually
complete with the dam approaching its maximum height of 35 m. Horizontal drainage blankets were
incorporated in both the upstream and the downstream shale fill shoulders. Piezometers had been
installed and pore pressures were being monitored in the foundation, in the clay core, and in the
shoulder fill. The failure surface passed through the boot shaped rolled clay core and a relatively thin
layer of surface clay in the foundation of the dam. Investigation of the events at Carsington has made
important contributions to the fundamental understanding of the behaviour of large earthworks of this
type (Vaughan et al., 1989; Dounias et al., 1996).
The objective of this research is to evaluate a detailed slope stability assessment of the Carsington Earth
Embankment Dam in the UK used to retain mine tailings.
By using and applying advanced geotechnical engineering analysis tools and modelling techniques the
Carsington Earth Embankment Dam, which is considered a particular geotechnical structure, is
analysed.
In the current detailed slope stability analyses the total and effective stress state soil properties /
parameters were used, and the most critical slip circle centre according to Fellenius - Jumikis method
was initially determined. Subsequently, the Carsington Earth Embankment Dam and its foundation was
analysed and examined against failure by slope instability. Considerations of loading conditions which
- 6021 -
2. Vol. 18 [2013], Bund. Z
6022
may result to instability for all likely combinations of reservoir and tailwater levels, seepage conditions,
both after and during construction were made, and hence three construction and / or loading conditions
were examined in particular:
• The right after Construction Condition,
• The Steady Seepage Condition, and
• The Rapid Drawdown Condition in the reservoir
In this context, the slope stability at the three above mentioned discrete loading cases of the Carsington
Earth Embankment Dam was analysed and presented, and certain valuable conclusions concerning the
overall stability conditions of the Earth Embankment Dam during its original construction are deduced
in this research paper.
In addition, for comparison reasons, a Slope Stability Analysis of the Carsington Earth Embankment
Dam during loading case (a) using Taylor’s curves was performed. Furthermore, the Shear Strength
Reduction (S.S.R.) Analysis Method, based on the Finite Element Analysis technique (F.E.A.), was
executed, for purposes of verification of the Global Slope Stability Analysis of the whole Carsington
Earth Embankment Dam for the Loading case (a), i.e. right after construction condition of the Dam but
prior to its filling with water, which proved that the results between the Shear Strength Reduction
(S.S.R.) Analysis Method and the Limit Equilibrium Analysis Method (LEM) based on the method of
slices are comparable and similar.
Finally, the reasons why the Fellenius - Jumikis method is inaccurate were examined, analysed and
explained, as well as the technical lessons learned from this large scale Earth Embankment Dam body
failure were pointed out.
KEYWORDS: Slope Stability Analysis; Earth Embankment Dams; Slope Failure; Embankment
Loading Conditions; Soil Properties / Parameters; Critical Slip Circle Centre Determination; Steady
Seepage Condition; Rapid Drawdown Condition; Shear Strength Reduction Analysis Method; Fellenius
- Jumikis Method; Computer Aided Slope Stability Analysis & Design.
INTRODUCTION
The British Regional Water Authority in Derbyshire as part of its water storage system in
order to regulate flows in the River Derwent, decided to construct a 35 m high and 1225 m long
zone earth filled embankment from 1981 to 1984. The Carsington Dam (Fig. 1) would be one of
the largest earth-fill dams in the UK. A 10 km long diversion tunnel would divert the water during
the winter and been stored in the reservoir of an estimated capacity of 35 million m3. When the
water level in the river was low, water would be released from the reservoir. The reservoir would
also facilitate as a rainwater runoff regulatory hydraulic system (Fig. 2).
The characteristics of the original construction of the Carsington Earth Embankment Dam, are
briefly described as follows. A shallow trench that was excavated upstream of the centreline into
the weathered gray foundation mudstone was connected to the central clayey core of the
embankment. Below the base of the trench a cut-off grout curtain extended. In the downstream and
upstream shells the earth fill was classified as Type A and Type B (Skempton and Vaughan,
1993). The Type A fill was described as a yellow brownish spotted clay with fine gravel < 5 mm
and pebbles of mudstone and was placed immediately upstream and downstream of the clay core.
The Type B soil was intended to be the same general type of material but without pebbles, and was
located in the outer portions of the shells. The representative cross sections of the original and
reconstructed Carsington Earth Embankment Dam are shown in Fig. 3 (Banyard et al., 1992).
3. Vol. 18 [2013], Bund. Z
6023
Figure 1: The study area of the Carsington Earth Embankment Dam in Derbyshire region,
UK
Figure 2: Close up of the reconstructed Carsington Earth Embankment Dam area.
4. Vol. 18 [2013], Bund. Z
6024
Figure 3: Representative cross sections of the original and reconstructed Carsington Earth
Embankment Dam (Banyard et al., 1992).
In 3 successive summer seasons during 1982, 1983, and 1984, the construction of the
embankment earth material moving would take place. The fill had reached almost 200 m in the
north valley and 197 m in the main section of the dam, at the end of the 1983 season. Earth
moving was resumed in April of 1984 and the embankment was completed to full height at the
north end and about 1 m short at the main section. Queries about the stability had been raised by
the Contractor and therefore, the Kennard Report, comprising a detailed review setting out clearly
the parameters used, the slip surfaces considered, the methods of analysis, and the resulting
Factors of Safety, was written. Concern was summarized in a statement that “a revised design was
essential if the dam was to be completed with confidence and safety”. It was fully expected that a
revised design would be prepared in the 1983/84 winter period. However, no meeting was held to
discuss the request, no change to the design was made.
Surprisingly, though, just before construction completion was reached, tension cracks were
first observed on the crest of the embankment on June 4 of 1984, when 1 m of crest remained to be
placed, over an approximate length of 65 m. A 400 m section of the upstream slope failed 36 hours
later, with a maximum horizontal displacement of almost 15 m.
According to Skempton and Coats, 1985 and Skempton and Vaughan, 1993, the exact incident
description is as follows. The failure started in the early hours of 4 June 1984 with a 50 mm crack
on the crest over a length of about 120 m. During the night of 5 June a major upstream slip
occurred. The slip propagated along the embankment in both directions extending to a length of
about 500 m, with an embankment crest slumping of 11 m, as shown in Fig. 4, and the upstream
toe moving 13 m horizontally by 6 June 1984. The initial slip sheared through the core which
already contained shear surfaces due to rutting and along a layer of yellow clay in the foundation
5. Vol. 18 [2013], Bund. Z
6025
which contained solifluction shears. Both materials were brittle with low residual strengths
(Skempton and Coats, 1985; Skempton and Vaughan, 1993).
Figure (4).Close up of the upstream slip failure surface of the Carsington earth embankment dam,
showing the slip propagated along the embankment with an embankment crest
slumping of 11 m (Environment Agency, 2011).
According to Johnston et al., 1999, exact wording: “…..Investigations indicated that the initial
slip resulted from shearing through the core and along a layer of yellow clay beneath the
foundation. In addition, there were a number of shear surfaces in the core caused by rutting from
construction plant. The yellow clay layer in the foundation was found to contain solifluction
shears, and the factor of safety reduced to 1.0 when strength reductions due to pre-existing shear
planes, progressive failure and lateral load transfer, were taken into account…..” (Johnston, 1995;
Johnston et al., 1999).
Remedial works and reconstruction of the failed dam is described by Banyard et al. (1992),
Chalmers et al. (1993), Macdonald et al. (1993) and Vaughan et al. (1991). It commenced in
February 1989 and was completed in 1991, seven years after the start of investigations. The main
differences in cross-section are shown in Fig. 3. Reconstruction of the new dam involved
excavation of two million cubic metres of the original dam to remove all failed material and lay a
sound foundation. The downstream view of the reconstructed Earth Embankment of the
Carsington Dam as stands nowadays is shown in Fig. 5.
6. Vol. 18 [2013], Bund. Z
6026
Figure (5).Downstream view of the reconstructed Earth Embankment of the Carsington Dam.
The failure of the Carsington Dam led to additional attention being given to the role of the
construction equipment and procedures in the subsequent stability of a structure. In this case, the
compaction equipment selected and the rate of fill placement are considered to have been key
factors in the observed failure. In addition, the importance of selecting instrumentation, which can
provide a precursor to a failure, was reinforced (Rowe, 1991).
Finally, in this research study, a detailed slope stability analysis was performed and presented
for three discrete loading cases of the Carsington Earth Embankment Dam construction and postconstruction stages, i.e. a) the right after Construction Condition [Loading case (a)], b) the Steady
Seepage Condition [Loading case (b)], and the Rapid Drawdown Condition [Loading case (c)].
From these detailed slope stability analysis results, the reasons as to why the Carsington Earth
Embankment Dam failed during its original construction became obvious.
EXAMINED ANALYSIS AND LOADING CONDITIONS
The Carsington Earth Embankment Dam and its foundation was analysed and designed against
failure by slope instability. Consideration of loading conditions which may result to instability
must be made for all likely combinations of reservoir and tailwater levels, seepage conditions, both
after and during construction. Three construction and / or loading conditions were examined in
particular:
a. The right after Construction Condition
The critical condition to be analysed is at the completion of embankment dam construction but
prior to filling with water.
In this case there is no water table present in the reservoir and in the embankment dam. Total
or undrained shear strength parameters of soils are used in this loading case.
7. Vol. 18 [2013], Bund. Z
6027
b. The Steady Seepage Condition
For zoned and homogeneous types of embankment dams and when the reservoir is full of
water and some steady seepage into the embankment is established, the conditions to be
considered for the steady state seepage analysis should be:
•
•
Steady state seepage pore pressures which are fully developed as a result of the reservoir have
being storing water over a long period of time. In this case there is a Phreatic Surface Line
under steady seepage state.
The combination of upstream and downstream water levels that is found to be the most
critical. In this research, this case is not examined.
Effective or drained shear strength parameters of soils are used in this loading case.
c. The Rapid Drawdown Condition in the reservoir
Fluctuations in reservoir water level may cause the upstream face stability to become critical
mainly due to the removal of the supporting water. When the reservoir is rapidly evacuated and
drawn down, pore water pressures in the dam body are reduced in two ways. There is a slower
dissipation of pore pressure due to drainage and there is an immediate elastic effect due to the
removal of the total or partial water load. The exact mechanism of this phenomenon is as follows:
It is assumed that the reservoir has been maintained at a high level for a sufficiently long time so
that the fill material of the dam is fully saturated and steady seepage established. If the reservoir is
drawn down at this stage, the direction of flow is reversed, causing instability in the upstream
slope of the earth dam. The “instantaneous” drawdown is a hypothetical condition that is assumed
and pore pressures along the sliding surface are determined by drawing the “instantaneous” flow
net. The most critical condition of sudden drawdown means that while the water pressure acting on
the upstream slope at “full reservoir” condition is removed, there is no appreciable change in the
water content of the saturated soil within the embankment. The saturated weight of the slope
produces the shearing stresses while the shearing resistance is decreased considerably because of
the development of the pore water pressures which do not dissipate rapidly (Ranjan, Rao, 2005).
Therefore, it was considered very important such an analysis to be carried out and included in this
research.
Hence, in this Rapid Drawdown Condition, there is no water table present in the reservoir but
in the embankment dam body there are still full pore water pressures. Effective or drained shear
strength parameters of soils are used in this loading case, too.
In the following Figures 1, 2 and 3, the Cross Section Views of the Carsington Earth
Embankment Dam model drawn in CAD, showing the internal water piezometric surface
trajectory, as well as the 3-D Model Views (Block Views) based on provided dimensions, are
presented on exact scale.
8. Vol. 18 [2013], Bund. Z
6028
Figure 6: Cross Section View of the Carsington Earth Embankment Dam model, based on
provided dimensions (On exact Scale).
Figure 7: Cross Section View of the Carsington Earth Embankment Dam model, showing the
internal water piezometric surface trajectory, based on provided dimensions (On exact
Scale).
Figure 8: 3-D Model Views (Block Views) of the Carsington Earth Embankment Dam, based on
provided dimensions (On exact Scale).
9. Vol. 18 [2013], Bund. Z
6029
GEOMETRY OF THE CARSINGTON EARTH
EMBANKMENT DAM PROFILE FOR SLOPE STABILITY
ANALYSIS
The general geometry and the foundation layers of the Carsington Earth Embankment Dam
profile is shown in Figure 4. It should be noted that this profile is not to scale.
Figure 9: Geometry (not to scale) of the cross section of the Carsington Earth Embankment Dam.
(Embankment Dam Profile for Slope Stability Analysis).
DETERMINATION OF THE X, Y COORDINATES OF
RELEVANT POINTS OF THE CARSINGTON EARTH
EMBANKMENT DAM CROSS SECTION
Based on the cross section geometry of the Carsington Earth Embankment Dam, the
determination and calculation of the accurate x, y coordinates of all relevant points of the “on the
scale cross-section diagram”, must be carried out. For this purpose, the following procedure was
executed. Let’s assume a1, a2, b1 and b2 lengths and point G are located as shown in Figure 5.
10. Vol. 18 [2013], Bund. Z
6030
Figure 10: a1, a2, b1 and b2 lengths calculation for the determination of the x, y coordinates of point G.
If trigonometric rules are applied to the “on the scale cross-section diagram”, then the
following equations can be formulated:
a1 + a2 = [30 / tan (tan-1(1/3))] - 33 + 10 - 3 = 64
and
a1 x tan (tan-1(1/5)) + a2 / tan (tan-1(1/4)) = 28
Therefore, solving these two equations of two unknowns, we can easily calculate a1 and a2
lengths, as follows:
a1 = 60 m, therefore b1 = 12 m
a2 = 4 m, therefore b2 = 16 m
Therefore, point’s G x, y coordinates are:
x = 93
y = 12
11. Vol. 18 [2013], Bund. Z
6031
According to the above mentioned coordinates of G point, as well as the geometry of the
Carsington Earth Embankment Dam as shown on Figure 4, the coordinates x, y of all other
relevant points and the structure interfaces were accurately determined, as shown in Table 1
below, considering x, y coordinates of the point marked with a back diamond in figure 5 as x = 5,
y =7.
Table 1: Depicted coordinates of all relevant points and structure interfaces of the Carsington
Earth Embankment Dam, considering x, y coordinates of the point marked with a back diamond as
x = 5, y =7.
#
Interface location
Coordinates of interface points [m]
x
y
x
y
x
y
-20.00
7.00
5.00
7.00
95.00
37.00
115.00
37.00
175.00
7.00
200.00
7.00
5.00
7.00
38.00
7.00
98.00
19.00
102.00
35.00
108.00
35.00
112.70
7.00
175.00
7.00
38.00
7.00
112.70
7.00
1
2
3
12. Vol. 18 [2013], Bund. Z
#
Interface location
6032
Coordinates of interface points [m]
x
y
x
y
x
y
-20.00
1.00
200.00
1.00
-20.00
-7.00
200.00
-7.00
4
5
Additionally, the coordinates of the Water Table Profile in the reservoir and inside the body of
the Carsington Earth Embankment Dam are also calculated and shown in tables 2 & 3. The water
level coordinates shown in table 2 are based on the Black Diamond, as shown in figure 5, having
coordinates of (x = 5, y =7).
Table 2: Coordinates of water level points based on the Black Diamond, as shown in figure 5,
having coordinates of (x = 5, y =7).
Water Profile
X coordinate Y coordinate
5
34
86
34
105
31
112.2
10
175
7
13. Vol. 18 [2013], Bund. Z
6033
Table 3: Depicted coordinates of water level points based on the Black Diamond, as shown in
figure 5, having coordinates of (x = 5, y =7).
#
GWT location
Coordinates of GWT points [m]
x
y
x
y
x
y
-20.00
34.00
86.00
34.00
101.00
34.00
105.00
31.00
112.20
10.00
114.00
8.00
175.00
7.00
200.00
7.00
1
All other points shown in Table 1 are then determined around the black diamond point, as well
as a list of the x, y coordinates was prepared for:
The Water Table Profile
The Foundation Ground Soil Layers
The Embankment Dam Soil Layers, and
The possible slip circle centres (given in a next chapter)
Finally, Figure 11 shows the illustration of x, y coordinates of all relevant points and structure
interfaces of the Carsington Earth Embankment Dam, including the water level, considering x, y
coordinates of the point marked with a back diamond as 5, 7.
Figure 11: Illustration of x, y coordinates of all relevant points and structure interfaces of the
Carsington Earth Embankment Dam, including the water level, considering x, y coordinates of the
point marked with a back diamond, as shown in figure 5, as x = 5, y =7.
14. Vol. 18 [2013], Bund. Z
6034
SOIL PROPERTIES / PARAMETERS IN TOTAL AND
EFFECTIVE STRESS STATE
The relevant properties / parameters of both natural (geological) and man-made soils in both
total (undrained) and effective (drained) stress state for the Slope Stability Analysis and Design are
presented in Table 5. Only the soil mechanics parameters and properties that are of concern and
interest for the slope stability analysis of the body of the Carsington Earth Embankment Dam are
given.
Table 5: Soil properties / parameters in total and effective stress state and legend.
#
Name
1
cef
γ
[°]
[kPa]
[kN/m3]
Clay Core
3
φef
Embankment Fill
2
Pattern
24.00
20.00
18.00
4.00
15.00
19.00
Firm Silty Clay
10.00
35.00
17.00
4
Stiff Sandy Clay
30.00
60.00
20.00
5
Impervious Bedrock
35.00
200.00
24.00
Soil parameters - uplift
#
Name
Pattern
γsat
φu
cu
[kN/m3]
[°]
[kPa]
1
Embankment Fill
19.00
25
40
2
Clay Core
20.00
0
125
3
Firm Silty Clay
18.00
0
50
4
Stiff Sandy Clay
21.00
15
80
5
Impervious Bedrock
24.00
35
200
15. Vol. 18 [2013], Bund. Z
6035
Soil properties / parameters in total and effective stress state
Embankment Fill
Unit weight :
Effective Angle of internal friction :
Effective Cohesion of soil :
Total Angle of internal friction :
Total Cohesion of soil :
Saturated unit weight :
γ
φef
cef
φu
cu
γsat
=
=
=
=
=
=
18.00 kN/m3
24.00 °
20.00 kPa
25.00 °
40.00 kPa
19.00 kN/m3
Clay Core
Unit weight :
Effective Angle of internal friction :
Effective Cohesion of soil :
Total Angle of internal friction :
Total Cohesion of soil :
Saturated unit weight :
γ
φef
cef
φu
cu
γsat
=
=
=
=
=
=
19.00 kN/m3
4.00 °
15.00 kPa
0.00 °
125.00 kPa
20.00 kN/m3
Firm Silty Clay
Unit weight :
Effective Angle of internal friction :
Effective Cohesion of soil :
Total Angle of internal friction :
Total Cohesion of soil :
Saturated unit weight :
γ
φef
cef
φu
cu
γsat
=
=
=
=
=
=
17.00 kN/m3
10.00 °
35.00 kPa
0.00 °
50.00 kPa
18.00 kN/m3
Stiff Sandy Clay
Unit weight :
Effective Angle of internal friction :
Effective Cohesion of soil :
Total Angle of internal friction :
Total Cohesion of soil :
Saturated unit weight :
γ
φef
cef
φu
cu
γsat
=
=
=
=
=
=
20.00 kN/m3
30.00 °
60.00 kPa
15.00 °
80.00 kPa
21.00 kN/m3
Impervious Bedrock (Conservative Values)
Unit weight :
γ
=
φef =
Effective Angle of internal friction :
cef =
Effective Cohesion of soil :
φu =
Total Angle of internal friction :
cu =
Total Cohesion of soil :
γsat =
Saturated unit weight :
24.00 kN/m3
35.00 °
200.00 kPa
35.00 °
200.00 kPa
24.00 kN/m3
The above mentioned soil mechanics parameters and properties either in total or in effective
stress state are assigned to each earth embankment dam surface (region) as follows.
Soil Assigning in the Carsington Earth Embankment Dam surfaces (regions)
#
Surface position
Coordinates of surface points [m]
x
y
x
y
Assigned
soil
17. Vol. 18 [2013], Bund. Z
#
Surface position
6037
Coordinates of surface points [m]
x
y
x
y
Assigned
soil
1
2
3
4
5
MOST CRITICAL SLIP CIRCLE CENTRE
DETERMINATION BY FELLENIUS - JUMIKIS METHOD
General
Before running any Slope Stability Analysis Computer programme (software), a scale diagram
of the Carsington Earth Embankment Dam was drawn and the Fellenius - Jumikis method
(Watson, 2012 & Murthy, 2003) was used in order to obtain a very approximate indication of the
location of the most critical slip circle centre in the Carsington Earth Embankment Dam.
Procedure for locating the Most Critical Circle
Since the determination of the minimum factor of safety for a slope is very crucial for the
design of the Carsington Earth Embankment Dam, it is important to locate the most critical slip
circle with as few trials as possible. In a random trial and error approach, the three geometric
parameters, namely, the centre of rotation, the radius of slipcircle and the distance of intercept in
front of the toe are varied and the minimum factor of safety obtained. This requires a very large
number of trials, but computers have made the method feasible. However, it is known that there is
a certain pattern in slip circle behaviour and a knowledge of this pattern can be used to advantage
and the number of trials reduced.
For instance, it is known that the most critical circle passes through the toe of the slope when
(a) the angle of shearing resistance φ is greater than 3°, and (b) the slope angle β exceeds 53°,
irrespective of the value of φ. The most critical circle intersects the slope in front of the toe if φ is
less than 3° and β < 53°.
Fellenius (1936) proposed an empirical procedure to find the centre of the most critical circle
in a φu = 0 soil. The centre Ο for the toe failure case can be located at the intersection of the two
lines drawn from the ends A and Β of the slope at angles α and ψ (Figure 7 (a)). The angles α and
ψ vary with the slope β. Table 6 gives these values.
18. Vol. 18 [2013], Bund. Z
6038
Figure 7: Location of critical circle (Ranjan, Rao, 2005).
Jumikis (1962) further extended this method to the case of a homogeneous, c' - φ' soil. After
obtaining the centre O1 for a φu = 0 soil, point Ρ is located at a distance 4.5 Η horizontally from
the toe of the slope and Η below the toe of the slope. The centre of the critical circle is then
assumed to lie on the extension of line PO1 and the factors of safety obtained are plotted to obtain
a locus from which the minimum factor of safety can be read [Figure 7 (a)].
For flat slopes or when the soil below the toe is softer than the slope material, the critical slip
circle will not be a toe circle but will reach much below the toe, resulting in what is called a “base
failure”. Fellenius showed that in a homogeneous, purely cohesive soil with slope angles less than
53°, the centre of rotation for the deep seated base failure lies on a vertical drawn through the midpoint of the slope and the central angle of the critical circle is about 133.5° [Figure 7 (b)]. Where a
stiffer layer of soil or rock lies beneath the slope, the most critical circle tends to be tangential to
this stratum (experience of Dr. C. Sachpazis).
Table 6: Fellenius's Criteria for Locating the of Most Critical Centre Circle of a Slope in a φu = 0
Soil.
Slope
Slope
Angle
Angle
Angle β
ratio
αo
ψo
60°
1 / 0.58
29°
40°
45°
1/1
28°
37°
33.8°
1 / 1.5
26°
35°
26.6°
1/2
25°
35°
18.4°
1/3
25°
35°
11.3°
1/5
25°
37°
The above guidelines can only serve as pointers and in any stability analysis a sufficiently
large number of trials have to be made to locate the correct critical circle. It is found that the factor
of safety is more sensitive to lateral shifting of the centre than to vertical movements. Moreover,
the guidelines according to Fellenius - Jumikis method, can only serve as a general and
approximate way for the determination of the critical slip circle centre.
The reasons of the Fellenius - Jumikis method inaccuracy mainly lie because of:
19. Vol. 18 [2013], Bund. Z
6039
a) The soils of the Carsington Earth Embankment Dam may not be purely φu = 0 soils, as
Fellenius (1936) proposed,
b) The soils of the Carsington Earth Embankment Dam may not be homogeneous c' - φ' soils,
(because there might be different soil layers in the sloping embankment body and different
soils in the impermeable core) as Jumikis (1962) assumed to further extended Fellenius’s
method,
c) The existence of water tables and pore water pressures are not taken into account in
Fellenius - Jumikis method,
d) Fellenius - Jumikis method becomes less reliable for non-homogeneous conditions, such
as irregular slope profile,
e) Surcharging and other type of loading of slopes is not taken into account in Fellenius Jumikis method, and
f) Seismic loading of slopes is not taken into account in Fellenius - Jumikis method. Seismic
loading deteriorates stability conditions and a special treatment is required, (Anastasiadis
et al, 2006).
Therefore, according to the above mentioned reasons of inaccuracy the determination of the
location of the most critical slip circle centre in an earth embankment dam by using Fellenius Jumikis method could not be accurate enough.
But nevertheless, the determination of the coordinates (x, y) of the location of the most critical
slip circle centre by using even the inaccurate Fellenius - Jumikis method can dramatically help to
advantage and reduce the number of computational trials needed.
Finally according to Watson (2012), “…..the methods of Fellenius and Jumikis are often
ignored, especially when doing computer analysis, but the ideas are sound and give a good first
guess for solving a slope instability problem - they can save a lot of time !”.
Location of Most Critical Circle in the Carsington Earth
Embankment Dam
By applying the above mention procedure, according to Fellenius - Jumikis method, the
following on scale diagram of the Carsington Earth Embankment Dam cross section was drawn
(Figure 8) and a very approximate indication of the location of the most critical slip circle centre in
the Carsington Earth Embankment Dam cross section was obtained, as shown in Figure 11. For
this determination, the following input data were taken into account:
Embankment Fill:
Unit weight
Effective Angle of internal friction:
Effective Cohesion of soil
Total Angle of internal friction:
Total Cohesion of soil
Slope Angle β
Angle αo
Angle ψo
γ
φef
cef
φu
cu
=
=
=
=
=
=
=
=
18.00 kN/m3
24.00°
20.00 kPa
25.00°
40.00 kPa
18.44°
25°
35°
20. Vol. 18 [2013], Bund. Z
6040
Figure 11: Part of the on scale cross section of the Carsington Earth Embankment Dam for
locating of the most critical slip circle centre according to Fellenius method.
Therefore, the coordinates (x, y) of the location of the most critical slip circle centre point (O1)
in the Carsington Earth Embankment Dam, as shown in Figure 12, are:
x = 61
y = 60
Figure 12: Coordinates (x, y) of the location of the most critical slip circle centre on the cross
section of the Carsington Earth Embankment Dam, according to Fellenius method.
However, it should be remembered that the determination of the location of the most critical
slip circle centre in the Carsington Earth Embankment Dam could not be accurate enough, and that
21. Vol. 18 [2013], Bund. Z
6041
it can only be used in order to dramatically help to reduce the number of the succeeding
computational trials needed.
Therefore, for running any Slope Stability Analysis Computer programme, as it is presented in
following chapters, the most probable “window”, where the potential centre of the most critical
slip circle might lie, will be arranged according to the above mentioned coordinates (x, y) values
of the location of the most critical slip circle centre point (O1) in the Carsington Earth
Embankment Dam as determined according to Fellenius - Jumikis method.
These values really did pay off in saving time, and ensured that the correct circle with the
lowest value of Factor of Safety (FoS) was found out.
SLOPE STABILITY ANALYSIS OF THE CARSINGTON
EARTH EMBANKMENT DAM USING BISHOP METHOD
General
The Carsington Earth Embankment Dam and its foundation was analysed and designed against
failure by slope instability.
Considerations of loading conditions which may result to instability for all likely combinations
of reservoir and tailwater levels, seepage conditions, both after and during construction were
made, and hence three construction and / or loading conditions were examined in particular, as
follows:
a. The right after Construction Condition.
The first critical condition to be analysed is at the completion of embankment dam
construction but prior to filling with water. [Loading case (a)]. In this case, there is no water table
present in the reservoir and in the embankment dam body. Total or undrained shear strength
parameters of soils are used in this loading case.
b. The Steady Seepage Condition.
The second critical condition to be analysed is when the reservoir is full of water and some
steady state seepage into the Carsington Earth Embankment Dam is established. [Loading case
(b)]. In this case, a Phreatic Surface under steady seepage state is present in the embankment dam
body. The Water Table Profile in the reservoir and inside the body of the Carsington Earth
Embankment Dam is shown in a previous section. Effective or drained shear strength parameters
of soils are used in this loading case.
c. The Rapid Drawdown Condition in the reservoir.
Rapid Drawdown in the reservoir water level may cause the upstream face stability to become
very critical mainly due to the removal of the supporting water and also due to the development of
the adverse seepage forces inside the embankment dam body during pore water pressure
dissipation process. In this case, there is no water table present in the reservoir but in the
embankment dam body there are still full pore water pressures. Effective or drained shear strength
parameters of soils are used in this loading case, too.
22. Vol. 18 [2013], Bund. Z
6042
Slope Stability Analysis Results for the right after
Construction Condition [Loading case (a)]
The analysis was performed using:
A model with the simulation of the Carsington Earth Embankment Dam body and its
foundation soil layers with all applied loads. The model was developed using exact dimensions
in an appropriate scale, as shown in Figure 10.
No water table in the reservoir and in the embankment dam body
Total or undrained shear strength parameters of soils
No seismic actions were taken into account
Bishop Method for Slope Stability Analysis
For performing the slope stability analysis for the right after construction condition [Loading
case (a)], the specialized Civil & Geotechnical Engineering computer Program Larix / Cubus was
used, operating according to E.U. Regulations, European Standard ENV 1997-1. Eurocode 7 (EC7) - ENV 1997-1.
The overall minimum stability factor of safety for the loading case (a), i.e. exactly after
construction of the Carsington Earth Embankment Dam but prior to filling with water, was
calculated equal to 0.96, which means imminent failure conditions. The computed analysis results
are illustrated in the following Figures (Fig. 13a and Fig. 13b).
Figure 13. Model setup for Slope Stability Analysis of the Carsington Earth Embankment Dam
exactly after construction of the embankment dam but prior to filling with water.
(Total shear strength parameters of soils - No water table present in the reservoir and
in the embankment dam body).
23. Vol. 18 [2013], Bund. Z
6043
Minimum FoS = 0.96
Figure 11a. Overall slope stability Factor of Safety for the loading case (a). Minimum FoS = 0.96,
which means imminent failure conditions. (Bishop Method).
RESULTS
------Design situation: Standard hazard scenario
SLIP CIRCLE WITH MINIMAL SAFETY
Circle
X
Y
R
CmP-No
Anchor
S-Fc
Denomin
L-req
No.
[m]
[m]
[m]
[kN]
[m]
---------------------------------------------------------------------24
55.92
73.56
70.00
0.96
6544.95
Figure 11b: Overall slope stability Factor of Safety for the loading case (a). Minimum FoS = 0.96,
which means imminent failure conditions. (Bishop Method).
24. Vol. 18 [2013], Bund. Z
6044
Slope Stability Analysis Results for the Steady Seepage
Condition [Loading case (b)]
The loading case (b) to be analysed is when the reservoir is full of water and some steady state
seepage into the Carsington Earth Embankment Dam is established.
The analysis was performed using:
A model with the simulation of the Carsington Earth Embankment Dam body and its
foundation soil layers with all applied loads. The model is shown in Figure 12
The exact Water Table Profile in the reservoir and inside the body of the Carsington Earth
Embankment Dam is shown in Table 4a & 4b
Effective or drained shear strength parameters of soils
No seismic actions were taken into account
Bishop Method for Slope Stability Analysis
For performing the slope stability analysis for the Steady Seepage Condition [Loading case
(b)], the same specialized Civil & Geotechnical Engineering computer Program Larix / Cubus was
used.
The overall minimum stability factor of safety for the loading case (b), i.e. when the reservoir
is full of water and some steady state seepage into the Carsington Earth Embankment Dam is
established, was calculated equal to 0.81, which means failure conditions. The computed analysis
results are illustrated in the following Figures (Fig. 13a and Fig. 13b).
Figure 12: Model setup for Slope Stability Analysis of the Carsington Earth Embankment Dam
when the reservoir is full of water and some steady seepage into the embankment is
established. (Effective shear strength parameters of soils - Phreatic Surface is present in the
embankment dam body and Water Table in the reservoir).
Figure 13a: Overall slope stability Factor of Safety for the loading case (b). Minimum FoS = 0.81,
which means failure conditions. (Bishop Method)
25. Vol. 18 [2013], Bund. Z
6045
RESULTS
------Design situation: Standard hazard scenario
SLIP CIRCLE WITH MINIMAL SAFETY
Circle
X
Y
R
CmP-No
Anchor
S-Fc
Denomin
L-req
No.
[m]
[m]
[m]
[kN]
[m]
---------------------------------------------------------------------22
65.63
57.10
50.00
0.81
2693.64
Figure 13b: Overall slope stability Factor of Safety for the loading case (b). Minimum FoS = 0.81,
which means failure conditions. (Bishop Method).
Slope Stability Analysis Results for the Rapid Drawdown
Condition [Loading case (c)]
The loading case (c) to be analysed is when there is a Rapid Drawdown in the reservoir water
level which may cause the upstream face stability to become very critical.
The analysis was performed using:
A model with the simulation of the Carsington Earth Embankment Dam body and its
foundation soil layers with all applied loads. The model is shown in Figure 14
No water table in the reservoir but in the embankment dam body there are still full pore water
pressures
Effective or drained shear strength parameters of soils
No seismic actions were taken into account
Bishop Method for Slope Stability Analysis
For performing the slope stability analysis in this loading case (c), the same software was
used, (Larix / Cubus).
The overall minimum stability factor of safety for the loading case (c), i.e. when there is a
Rapid Drawdown in the reservoir water level, was calculated equal to 0.50, which means absolute
& immediate failure conditions. The computed analysis results are illustrated in the following
Figures (Fig. 15a and Fig. 15b).
26. Vol. 18 [2013], Bund. Z
6046
Figure 14: Model setup for Slope Stability Analysis of the Carsington Earth Embankment Dam in
Rapid Drawdown Condition in the reservoir. (Effective shear strength parameters of soils Phreatic Surface is present in the embankment dam body but no Water Table is present in the
reservoir).
Minimum FoS = 0.50
Figure 15a: Overall slope stability Factor of Safety for the loading case (c). Minimum FoS = 0.50,
which means absolute & immediate failure conditions. (Bishop Method).
27. RESULTS
------Design situation: Standard hazard scenario
SLIP CIRCLE WITH MINIMAL SAFETY
Circle
X
Y
R
CmP-No
Anchor
S-Fc
Denomin
L-req
No.
[m]
[m]
[m]
[kN]
[m]
---------------------------------------------------------------------22
65.63
57.10
50.00
0.50
4800.86
Figure 15b: Overall slope stability Factor of Safety for the loading case (c). Minimum FoS =
0.50, which means absolute & Immediate failure conditions. (Bishop Method).
GLOBAL SLOPE STABILITY ANALYSIS OF THE
CARSINGTON EARTH EMBANKMENT DAM USING THE
SHEAR STRENGTH REDUCTION ANALYSIS METHOD
(F.E.A.)
For purposes of verification of the Global Slope Stability Analysis of the whole Carsington
Earth Embankment Dam, for the Loading case (a), i.e. right after construction condition of the
Carsington Earth Embankment Dam but prior to filling with water, the Shear Strength Reduction
(S.S.R.) Analysis Method, based on the Finite Element Analysis technique (F.E.A.), was
executed.
For performing the Shear Strength Reduction (S.S.R.) Analysis the specialized Civil &
Geotechnical Engineering computer program Phase2 8 / Rocscience Inc was used.
The analysis results showed that the critical slope side of the Carsington Earth Embankment
Dam right after its construction is the downstream slope side.
As proved, the global Factor of Safety (FoS) or the Strength Reduction Factor (S.R.F.)
according to the Shear Strength Reduction (S.S.R.) Analysis Method for the whole Carsington
Earth Embankment Dam structure is: 0.85, which means failure conditions for the dam.
In the next Figures (Fig. 16 to 19) the following information of the Shear Strength Reduction
(S.S.R.) Analysis Model is concisely illustrated:
- 6047 -
28. Vol. 18 [2013], Bund. Z
All Input Data
The Mesh and Discretization
The Mesh and boundary conditions,
The Material Properties Definition,
The Material Properties Assignment to the Earth Embankment Dam model,
The final Analysis Results of the Strength Reduction Factor (S.R.F.)
General Settings
•
•
•
•
Single stage model
Analysis Type: Plane Strain
Solver Type: Gaussian Elimination
Units: Metric, stress as kPa
Analysis Options
•
•
•
•
•
•
Maximum Number of Iterations: 500
Tolerance: 0.001
Number of Load Steps: Automatic
Convergence Type: Absolute Energy
Tensile Failure: Reduces Shear Strength
Joint tension reduces joint stiffness by a factor of 0.01
Strength Reduction Settings
•
•
•
•
•
•
Initial Estimate of SRF: 1
Step Size: Automatic
Tolerance (SRF): 0.01
Limit SSR Search Area: No
Apply SSR to Mohr-Coulomb Tensile Strength: Yes
Convergence Parameters: Automatic
Groundwater Analysis
•
•
•
Method: Piezometric Lines
Pore Fluid Unit Weight: 9.81 kN/m3
Probability: None
Field Stress
•
•
•
•
•
•
Field stress: gravity
Using actual ground surface
Total stress ratio (horizontal/vertical in-plane): 1
Total stress ratio (horizontal/vertical out-of-plane): 1
Locked-in horizontal stress (in-plane): 0
Locked-in horizontal stress (out-of-plane): 0
•
•
•
Mesh type: uniform
Element type: 6 nodded triangles
Number of elements: 2773
Mesh
6048
29. Vol. 18 [2013], Bund. Z
•
6049
Number of nodes: 5764
Mesh Quality
•
All elements are of good quality
Poor quality elements defined as:
Side length ratio (maximum / minimum) > 30.00
•
•
Minimum interior angle < 2.0 degrees
•
Maximum interior angle > 175.0 degrees
Figure 16: Mesh and Discretization Mesh and default boundary conditions.
Figure 17: Mesh and Discretization Free boundary condition applied to ground surface.
31. Vol. 18 [2013], Bund. Z
6051
Figure 18: Mesh Material Properties Assigned to the Carsington Earth Embankment Dam model.
Minimum S.R.F. = 0.85
Figure 19: Analysis results of the Shear Strength Reduction Factor. (Indicates Failure).
32. SLOPE STABILITY ANALYSIS OF THE CARSINGTON
EARTH EMBANKMENT DAM DURING LOADING CASE
(A) USING TAYLOR’S CURVES
General
Taylor (1937) published a set of charts that relate stability coefficient, Ns to slope angle, β, in
order to make the search for the lowest value of FoS easier. The charts assume the soil to be
homogeneous and relate to total stress only.
Based on the principle of geometric similarity, Taylor (1937) published stability coefficients
for the analysis of homogeneous slopes in terms of total stress. For a slope of height H as shown in
Figure 20, the stability coefficient (Ns) for the failure surface along which the factor of safety
(FoS) is a minimum is given by
Ns =
cu
FγH
Figure 20: Taylor’s stability coefficients for φu = 0 (Craig, 2004).
For the case of φu = 0, values of Ns can be obtained from Figure 20. The coefficient Ns
depends on the slope angle β and the depth factor D, where DH is the depth to a firm stratum.
- 6052 -
33. Vol. 18 [2013], Bund. Z
6053
Gibson and Morgenstern (1962) published stability coefficients for slopes in normally
consolidated clays in which the undrained strength cu (φu = 0) varies linearly with depth.
Taylor’s chart is also conservative in that an increase in φu leads to a reduction in Ns and
consequent increase in the factor of safety (FoS), because if a slope stands up at φu = zero it will
always stand up at greater φ.
Calculation of the FoS against a slip failure occurring during
loading case (a) using Taylor’s curves
According to research’s requirements, the safety factor against a slip failure occurring during
loading case (a) using Taylor’s curves must be calculated.
Hence, following the above mentioned procedure and Taylor’s stability coefficients curves,
that was achieved for our case study for the loading case (a), i.e. exactly after construction of the
Carsington Earth Embankment Dam but prior to filling with water, as follows.
For this analysis using Taylor’s curves, the following input data were taken into account:.
Embankment Fill:
Unit weight
Total Angle of internal friction:
Total Cohesion of soil
Slope Angle β
γ
φu
cu
=
=
=
=
18.00 kN/m3
25.00°
40.00 kPa
18.5°
For applying the above mentioned procedure, the following on scale diagram of the Carsington
Earth Embankment Dam cross section was considered, as shown in Figure 21.
Figure 21: Part of the on scale cross section of the Carsington Earth Embankment Dam for the
calculation of the FoS against a slip failure occurring during loading case (a) using
Taylor’s curves.
Therefore, the minimum factor of safety against a slip failure occurring during loading case (a)
using Taylor’s curves can be estimated by using the stability coefficient (Ns). From Figure 21, β =
18.45o and D = 1, the value of Ns is 0.10. Then
F=
cu
N sγH
34. Vol. 18 [2013], Bund. Z
6054
F=
40
0.10 x18 x30
F = 0.741
Therefore, the factor of safety (FoS) against a slip failure occurring during loading case (a)
using Taylor’s curves is as low as F = 0.741, which means failure conditions of the Carsington
Earth Embankment Dam exactly after construction of the embankment dam but prior to filling
with water.
However, in this point an important conclusion can be drawn. If we compare the factor of
safety (FoS) against a slip failure occurring during loading case (a) as calculated by using Taylor’s
curves method with the FoS as calculated by the moment equilibrium Bishop’s method and
presented in previous section, we can see that the FoS calculated by Taylor’s curves method is
lower by 22,8 %.
Actually, this fact is reasonable and it was expected for two main reasons:
a) In Taylor’s curves method, the beneficial for the stability effect of the undrained angle of
internal friction, which is greater than 0, is not taken into account, and
b) In Taylor’s curves method, the beneficial effect of the Clay Core soil, which has an
undrained cohesion greater than the undrained cohesion of the Embankment Fill soil, is
not taken into account either.
Therefore, the lower resulted value of the FoS when using Taylor’s curves method compared
to the higher resulted value of the FoS when using the moment equilibrium Bishop’s method is
fully justified and expected.
SUMMARY, DISCUSSION AND CONCLUSIONS
A detailed slope stability analysis and assessment of the original Carsington Earth
Embankment Dam failure in the UK was attempted in this paper.
A 1225 m long, 35 m high zone earth filled embankment was being constructed from 1981 to
1984 from a British Regional Water Authority to regulate flows in the River Derwent in England.
Its reservoir capacity was 35 million m3 and the watertight element was Rolled Clay Core with an
upstream extension of boot shaped and shoulders of compacted mudstone with horizontal drainage
layers of crushed limestone about 4 metres apart and a cut-off grout curtain (Davey and Eccles,
1983).
However, at the beginning of June 1984, a 400 m length of the upstream shoulder of the
embankment dam slipped some 11 m and failed. At the time of the failure, embankment
construction was virtually complete with the dam approaching its maximum height of 35 m. The
failure surface passed through the boot shaped rolled clay core and a relatively thin layer of
surface clay in the foundation of the dam.
35. Vol. 18 [2013], Bund. Z
6055
By using and applying advanced geotechnical engineering analysis tools and modelling
techniques the Carsington Earth Embankment Dam, which is considered a particular geotechnical
structure, was analysed in this paper.
In this detailed slope stability analyses, the total and effective stress state soil properties /
parameters were used, and the most critical slip circle centre according to Fellenius - Jumikis
method was initially determined. Subsequently, the Carsington Earth Embankment Dam and its
foundation was analysed and examined against failure by slope instability. Considerations of
loading conditions which may result to instability for all likely combinations of reservoir and
tailwater levels, seepage conditions, both after and during construction were made, and hence three
construction and / or loading conditions were examined in particular:
•
•
•
The right after Construction Condition [Loading case (a)],
The Steady Seepage Condition [Loading case (b)], and
The Rapid Drawdown Condition in the reservoir [Loading case (c)]
In this context, the slope stability at the three above mentioned discrete loading cases of the
Carsington Earth Embankment Dam was analysed and presented, and certain valuable conclusions
concerning the overall stability conditions of the Earth Embankment Dam during its original
construction were deduced in this research paper.
In addition, for comparison reasons, a Slope Stability Analysis of the Carsington Earth
Embankment Dam during loading case (a) using Taylor’s curves was performed. Furthermore, the
Shear Strength Reduction (S.S.R.) Analysis Method, based on the Finite Element Analysis
technique (F.E.A.), was executed, for purposes of verification of the Global Slope Stability
Analysis of the whole Carsington Earth Embankment Dam for the Loading case (a), i.e. right after
construction condition of the Dam but prior to its filling with water, which proved that the results
between the Shear Strength Reduction (S.S.R.) Analysis Method and the Limit Equilibrium
Analysis Method (LEM) based on the method of slices are comparable and similar.
From these detailed slope stability analysis results, the reasons as to why the Carsington Earth
Embankment Dam failed during its original construction became obvious.
According to the detailed slope stability analysis results, the following conclusions can be
deduced when considering the three examined construction and / or loading conditions:
a) The overall minimum stability
factor of safety for the loading case
(a), i.e. exactly right after
construction of the Carsington
Earth Embankment Dam but prior
to filling with water, was
calculated equal to 0.96, which
means imminent failure conditions.
36. Vol. 18 [2013], Bund. Z
6056
b) The overall minimum stability
factor of safety for the loading case
(b), i.e. when the reservoir is full of
water and some steady state
seepage into the Carsington Earth
Embankment Dam is established,
was calculated equal to 0.81, which
means failure conditions.
c) The overall minimum stability
factor of safety for the loading case
(c), i.e. when there is a Rapid
Drawdown in the reservoir water
level, was calculated equal to 0.50,
which
means
absolute
&
immediate failure conditions.
For purposes of verification of the Global Slope Stability Analysis of the whole Carsington
Earth Embankment Dam structure at the Loading case (a), the Shear Strength Reduction (S.S.R.)
Analysis Method was executed, based on the Finite Element Analysis technique (F.E.A.). As
proved, the global Factor of Safety (FoS) or the Strength Reduction Factor (S.R.F.) for the whole
Carsington Earth Embankment Dam structure was determined equal to 0.85, which means failure
conditions for the dam.
In addition, for comparison reasons, a Slope Stability Analysis of the Earth Embankment Dam
during loading case (a) using Taylor’s curves was performed, and showed that the factor of safety
(FoS) against a slip failure occurring during loading case (a) was as low as F = 0.741, which
means failure conditions of the Carsington Earth Embankment Dam.
However, if the factor of safety (FoS) against a slip failure occurring during loading case (a) as
calculated by using Taylor’s curves method, is compared to the FoS as calculated by the moment
equilibrium Bishop’s method, it can be seen that the FoS calculated by Taylor’s curves method is
lower by 22,8 %. Actually, this fact is considered reasonable and it was expected for two main
reasons:
a) In Taylor’s curves method, the beneficial for the stability effect of the undrained angle of
internal friction, which is greater than 0, is not taken into account, and
37. Vol. 18 [2013], Bund. Z
6057
b) In Taylor’s curves method, the beneficial effect of the Clay Core soil, which has an
undrained cohesion greater than the undrained cohesion of the Embankment Fill soil, is
not taken into account either.
Therefore, the lower resulted value of the FoS when using Taylor’s curves method is fully
justified and expected.
Moreover, the reasons why the Fellenius - Jumikis method is inaccurate can be summarised as
follows:
a) The soils of the Carsington Earth Embankment Dam may not be purely φu = 0 soils, as
Fellenius (1936) proposed,
b) The soils of the Carsington Earth Embankment Dam may not be homogeneous c' - φ' soils,
(because there might be different soil layers in the sloping embankment body and different
soils in the impermeable core) as Jumikis (1962) assumed to further extended Fellenius’s
method,
c) The existence of water tables and pore water pressures are not taken into account in
Fellenius - Jumikis method,
d) Fellenius - Jumikis method becomes less reliable for non-homogeneous conditions, such
as irregular slope profile,
e) Surcharging and other type of loading of slopes is not taken into account in Fellenius Jumikis method, and
f) Seismic loading of slopes is not taken into account in Fellenius - Jumikis method. Seismic
loading deteriorates stability conditions and a special treatment is required, (Anastasiadis
et al, 2006).
Therefore, due to the above mentioned reasons of inaccuracy the determination of the location
of the most critical slip circle centre in an earth embankment dam by using Fellenius - Jumikis
method could not be accurate enough. But nevertheless, this determination can dramatically help
to advantage and reduce the number of computational trials needed.
According to all above mentioned results, derived from the slope stability analyses, became
obvious and well documented why the original Carsington Earth Embankment Dam failed just
upon its construction completion at the beginning of June 1984.
Based on the results of this research study as well as the observations made by Johnston et al.,
1999, the causes of failure of the Carsington Earth Embankment Dam can be summarized as
follows:
•
•
•
•
Two different figures of Factor of Safety were used for the upstream and downstream
slopes showing that the slope and zoning had not been designed to meet a minimum
Factor of Safety.
During construction, the Contractor found the requirements for testing and removing clay
from the foundation to be inconsistent resulting in weak material being left in place.
None of the assumed slip surfaces, of which the Consulting Engineers stated that were
analyzed, passed through the upper part of the core boot section, or the upstream
fill/foundation junction.
It was apparent that the Factors of Safety were obviously too low for the structure.
38. Vol. 18 [2013], Bund. Z
6058
Finally, the technical and engineering lessons learned from this large scale Earth Embankment
Dam body failure can be summarized as follows:
•
•
•
•
•
•
Correct and conservative shear strength parameters should be used,
Realistic pore pressure assumptions should be made,
Accepted minimum Factors of Safety should be used,
Critical slip surfaces and global slope stability should be rigorously analyzed,
Instrumentation should be planned related to the design, and
A design report should be prepared and reviewed by a panel of experts or other advisors
and geotechnical engineering consultants.
Essential lessons learned during construction include:
•
•
The design should be reassessed when further strength and performance data are obtained,
The design Factors of Safety should be re-examined, and
•
The technical data and review should be available to the site, contractor and client as
required.
REFERENCES
1. Anastasiadis, A., Kambouris, A., Pavlidis I., (2006), "Rapid visual pre-earthquake
inspection of concrete dams", 15th CONCRETE Congress, Oct. 25 to 27, 2006
Alexandroupolis, Greece, Pp. 56-65, Volume II.
2. Banyard J K, Coxon R E and Johnston T A (1992). Carsington reservoir reconstruction of the dam. Proceedings of Institution of Civil Engineers, Civil
Engineering, 92(3), 106-115.
3. Barnes, G. E., (2010), Soil mechanics: principles and practice (3rd ed.), Basingstoke:
Palgrave Macmillan.
4. Bathe, K-J., (1982), "Finite Element Procedures in Engineering Analysis", PrenticeHall.
5. Bishop, A.W. (1955) The use of the slip circle in the stability analysis of slopes,
Geotechnique,5 (1), 7–17.
6. Bowles, J.E., (1997). Foundation Analysis and Design. 5th Edn., McGraw-Hill, New
York.
7. British Standard 6031 (1981) Code of Practice for Earthworks, British Standards
Institution, London.
8. Building Research Establishment (1990) An Engineering Guide to the Safety of
Embankment Dams in the United Kingdom, Watford.
9. Casagrande, A. (1937). "Seepage through dams," J.N. Engl. Waterworks Assoc. Ll(2).
10. Casagrande, A. (1940). Seepage through dams, in Contributions to Soil Mechanics
1925 - 1940, Boston Society of Civil Engineers, Boston, MA, pp. 295-336.
11. Chalmers R W, Vaughan P R and Coats D J (1993). Reconstructed Carsington dam:
design and performance. Proceedings of Institution of Civil Engineers, Water
39. Vol. 18 [2013], Bund. Z
6059
Maritime and Energy, 101(1), 1-16.
12. Craig, R.F. (2004), “Craig’s Soil Mechanics”, Seventh edition, Spon Press.
13. Davey P G And Eccles P G (1983). The Carsington scheme - reservoir and aqueduct.
Journal of Institution of Water Engineers and Scientists, 37(3), 215-239.
14. Dounias G T, Potts D M and Vaughan P R (1996). Analysis of progressive failure and
cracking in old British dams. Geotechnique, 46(4), 621-640.
15. Environment Agency, (2011). Evidence Report – Lessons from historical dam
incidents. Horizon House, Deanery Road, Bristol, BS1 5AH. ISBN: 978-1-84911-2321.
16. Fellenius, W. 1936. “Calculation of the Stability of Earth Dams,” Transactions, 2nd
International Congress on Large Darns, International Commission on Large Dams,
Washington, DC, pp 445-459.
17. Gibson, R.E. and Morgenstern, N.R. (1962) A note on the stability of cuttings in
normally consolidated clays, Geotechnique, 12 (3), 212–16.
18. Johnston T A (1995). Contribution of remedial works to Upper Glendevon dam,
Scotland. Transactions of Eighteenth International Congress on Large Dams, Durban,
5, 237-245.
19. Johnston T A, Millmore J P, Charles J A and Tedd P (1999). An engineering guide to
the safety of embankment dams in the United Kingdom (second edition). Building
Research Establishment report BR363. BRE, Garston, Watford.
20. Jumikis, A. R. 1962. “Active and Passive Earth Pressure Coefficient Tables,”
Engineering Research Publication No. 43, Rutgers University, New Brunswick, NY.
21. Kennard, M. F., and E. N. Bromhead. "Carsington Dam—The Near-Miss Which
Became
a
Bulls-Eye."
ASCE.org.
ASCE.
Web.
<http://cedb.asce.org/cgi/WWWdisplay.cgi?120883>.
22. Knappett, J.A. and Craig, R. F., (2012), Craig’s Soil Mechanics (8th Ed), Spon Press
23. Lambe T.W. & R.V. Whitman, “Soil Mechanics”, SI Version, 1979, John Wiley &
Sons.
24. Macdonald A, Dawson G M and Coleshill D C (1993). Reconstructed Carsington
dam: construction. Proceedings of Institution of Civil Engineers, Water Maritime and
Energy, 101(1), 17-30.
25. Murthy, V. N. S. (2003). “Civil & Geotechnical Engineering: Principles and Practices
of Soil Mechanics and Foundation Engineering”, Marcel Dekker, Inc. Pages: 1029.
26. Ranjan Gopal, Rao, A.S.R., (2005). “Basic And Applied Soil Mechanics”, New Age
International (P) Ltd., Publishers. ISBN: 81-224-1223-8. Pages: 758.
27. Rowe, P.W., (1991), "A Reassessment of the Causes of the Carsington Embankment
Failure", Geotechnique, Vol. 41, No.3, pp. 395-421.
28. Sachpazis, C.I. (1988), "Geotechnical Site Investigation Methodology for Foundation
of Structures". Published in the Bulletin of the Public Works Research Centre. Greece.
Edition January - June 1988.