This document summarizes a review of stone column settlement performance in compressible soils. It presents a new database of settlement improvement factors (n) calculated from over 20 case studies of stone column-improved ground. The database shows that n, a measure of settlement reduction, is generally predicted well by Priebe's improvement factor method. Additionally, n reflects the construction method, with dry bottom feed columns consistently outperforming other methods. The discussion considers how the stone column friction angle and construction technique affect settlement.
Vibro replacement stone columns are a ground improvement technique to improve the load bearing capacity and reduce the settlement of the soil. On many occasions, it is noted that the local soil is, by nature, unable to bear the proposed structure, so the use of ground improvement techniques may be necessary. Use of stone columns is one such technique. The stone column consists of crushed coarse aggregates of various sizes. The ratio in which the stones of different sizes will be mixed is decided by design criteria
Ground improvement technioques for high waysAMIT SHIDURKAR
'Ground improvement technioques for high ways' powerpoint presentation for civil engineering students. before any construction we should be well known about the characteristics of strata present at site and also how to improve bearing capacity of the soil. this presentation is focused on improvement of ground for construction of highways...!! for more powerpoints related to civil engineering you can contact me anytime on my mail id shidurkar007@gmail.com
Performance of square footing resting on laterally confined sandeSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Vibro replacement stone columns are a ground improvement technique to improve the load bearing capacity and reduce the settlement of the soil. On many occasions, it is noted that the local soil is, by nature, unable to bear the proposed structure, so the use of ground improvement techniques may be necessary. Use of stone columns is one such technique. The stone column consists of crushed coarse aggregates of various sizes. The ratio in which the stones of different sizes will be mixed is decided by design criteria
Ground improvement technioques for high waysAMIT SHIDURKAR
'Ground improvement technioques for high ways' powerpoint presentation for civil engineering students. before any construction we should be well known about the characteristics of strata present at site and also how to improve bearing capacity of the soil. this presentation is focused on improvement of ground for construction of highways...!! for more powerpoints related to civil engineering you can contact me anytime on my mail id shidurkar007@gmail.com
Performance of square footing resting on laterally confined sandeSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
A case study on soft soil improvement of hanoi haiphong expressway project in...HoangTienTrung1
A case of using Sand Compaction Pile method to improve the foundation soil for expressway in Vietnam is presented. The sand compaction pile (SCP) method, which forms a composite ground by driving the pile made of compacted sands into soft ground, is one of the commonly used soil improvement techniques in Viet Nam. The SCP method used to improve the ground through the increase of bearing capacity, which is achieved by improving loose sandy soils or accelerating the consolidation of soft clay soils. Within the country where the condition of sand purchase is abundant in Viet Nam, sand compaction pile were often used for soft ground improvement to replace the Load Relief Slab and Soil-Cement Column at Hanoi-Haiphong Expressway Project recently. The procedures used for soil improvement, the instrumentation and the field monitoring data are described. A few observational methods based on settlement records are available to predict future settlement and consolidation behavior, namely the hyperbolic (Tan 1971; Chin 1975) and Asaoka (Asaoka 1978) method. The field data were from the Thai Binh Bridge approached embankment construction at Hanoi-Haiphong Expressway Project.
The presentation illustrates a technique for ground improvement, Grouting. In India, grouting is still not being used very much. In this presentation, I have demonstrated the basic types of grouting, goals of ground improvement and two case studies of grouting.
EFFECT OF GROUTING ON STABILITY OF SLOPE AND UNSUPPORTED STEEP EXCAVATIONLakshmi Narayanan
Analysis of slopes for stability and safety is a major area of concern in civil engineering. To measure the effect of grouting on stability of slope, a scaled down prototype is created and cement grouting is applied by penetration method. The major finding of this project is a comparative study is based on application of grouting and the performance of the soil slope without grouting.
Objectives of the project
To determine the characteristics of soil and grouting materials.
To determine the physical properties and their applicability in different type of soil.
The main aim of the project is to find the effect of grouting on stability of slope.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
A case study on soft soil improvement of hanoi haiphong expressway project in...HoangTienTrung1
A case of using Sand Compaction Pile method to improve the foundation soil for expressway in Vietnam is presented. The sand compaction pile (SCP) method, which forms a composite ground by driving the pile made of compacted sands into soft ground, is one of the commonly used soil improvement techniques in Viet Nam. The SCP method used to improve the ground through the increase of bearing capacity, which is achieved by improving loose sandy soils or accelerating the consolidation of soft clay soils. Within the country where the condition of sand purchase is abundant in Viet Nam, sand compaction pile were often used for soft ground improvement to replace the Load Relief Slab and Soil-Cement Column at Hanoi-Haiphong Expressway Project recently. The procedures used for soil improvement, the instrumentation and the field monitoring data are described. A few observational methods based on settlement records are available to predict future settlement and consolidation behavior, namely the hyperbolic (Tan 1971; Chin 1975) and Asaoka (Asaoka 1978) method. The field data were from the Thai Binh Bridge approached embankment construction at Hanoi-Haiphong Expressway Project.
The presentation illustrates a technique for ground improvement, Grouting. In India, grouting is still not being used very much. In this presentation, I have demonstrated the basic types of grouting, goals of ground improvement and two case studies of grouting.
EFFECT OF GROUTING ON STABILITY OF SLOPE AND UNSUPPORTED STEEP EXCAVATIONLakshmi Narayanan
Analysis of slopes for stability and safety is a major area of concern in civil engineering. To measure the effect of grouting on stability of slope, a scaled down prototype is created and cement grouting is applied by penetration method. The major finding of this project is a comparative study is based on application of grouting and the performance of the soil slope without grouting.
Objectives of the project
To determine the characteristics of soil and grouting materials.
To determine the physical properties and their applicability in different type of soil.
The main aim of the project is to find the effect of grouting on stability of slope.
Experimental and Analytical Study on Uplift Capacity -Formatted Paper.pdfSamirsinh Parmar
Horizontal Plate Anchor,
Cohesion less soil,
Uplift anchor,
The uplift capacity of the anchor,
Breakout factor,
ground anchors,
Experimental analysis,
Analytical Verification,
Embedment Ratio
Effect of encasement length on geosynthetic reinforced stone columnseSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology.
Field and Theoretical Analysis of Accelerated Consolidation Using Vertical Dr...inventionjournals
Mumbai is the region consisting of soft compressible marine clay deposits. There are several construction problems on such soils and thus ground improvement is need to be carried out. Vertical drains is generally preferred technique as accelerated settlement is achieved during the construction phase itself if planned accordingly. The concept of vertical drains is based on the theory of three dimensional consolidation as described by Terzaghi (1943). Based on this concept, a consolidation programme is developed and an attempt is made to determine the field to laboratory coefficient of vertical consolidation ratio by Taylor’s Square Root of Time Method and Casagrande’s Logarithm of Time Fitting Method for this region. Based on this, the rate of consolidation and time required for consolidation in the field can be determined knowing the consolidation parameters. Equations are developed by using output of the programme and it is explained.
FIELD AND THEORETICAL ANALYSIS OF ACCELERATED SETTLEMENT USING VERTICAL DRAINS ijiert bestjournal
Mumbai is the region consisting of soft compressibl e marine clay deposits. There are several construction problems on such soils and thu s ground improvement need to be carried out. Vertical drains is generally preferred technique as accelerated settlement is achieved during the construction phase itself. The concept of vertical drains is based on three dimensional consolidation as described by Ter zaghi (1943). Based on this concept,a settlement programme is being developed and an at tempt is made to determine the field to laboratory coefficient of vertical consoli dation ratio by methods proposed by Taylor and Asaoka (1978) for this region by conside ring the case studies namely 1.) Mulund Airoli Bridge approach embankment 2.) Palm B each Marg. Based on this ratio,the rate of consolidation and time required for con solidation in the field can be determined knowing the consolidation parameters.
Influence of Dense Granular Columns on the Performance of Level and Gently Sl...Mahir Badanagki, Ph.D.
Dense granular columns are often used as a liquefaction mitigation measure to (1) enhance drainage; (2) provide shear reinforcement; and (3) densify and increase lateral stresses in the surrounding soil during installation. However, the independent influence and contribution of these mitigation mechanisms on the excess pore pressures, accelerations (or shear stresses), and lateral and vertical deformations are not sufficiently understood to facilitate a reliable design. This paper presents the results of a series of dynamic centrifuge tests to fundamentally evaluate the influence of dense granular columns on the seismic performance of level and gently sloped sites, including a liquefiable layer of clean sand. Specific consideration was given to the relative importance of enhanced drainage and shear reinforcement. Granular columns with greater area replacement ratios (Ar), for example Ar greater than about 20%, were shown to be highly effective in reducing the seismic settlement and lateral deformations in gentle slopes, owing primarily to the expedited dissipation of excess pore water pressures. The influence of granular columns on accelerations (and therefore, the shear stress demand) in the surrounding soil depended on the column’s Ar and drainage capacity. Increasing Ar from 0 to 10% was shown to reduce the accelerations across a range of frequencies in the surrounding soil due to the shear reinforcement effect alone. However, enhanced drainage simultaneously increased the rate of excess pore pressure dissipation, helping the surrounding soil regain more quickly its shear strength and stiffness. At short drainage distances or higher Ar values (for example, 20%), this could notably amplify the acceleration and shear stress demand on soil, particularly at greater frequencies that influence PGA. The experimental insight presented in this paper aims to improve our understanding of the mechanics of liquefaction and lateral spreading mitigation with granular columns, and it may be used to validate the numerical models used in their design.
BIM is an acronym of the moment in the construction industry. But how far has it penetrated into routine geotechnical engineering practice? This presentation shows what can be done and sets some challenges for the foundation construction industry.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
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Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
"A Review of the Settlement of Stone Columns in Compressible Soils"
1. A Review of the Settlement of Stone Columns in Compressible Soils
Bryan A. McCabe1
CEng MIEI and Derek Egan2
CEng MICE
1
Lecturer in Civil Engineering, School of Engineering and Informatics, National University of Ireland,
Galway, Ireland. bryan.mccabe@nuigalway.ie
2
Chief Engineer, Keller Foundations, Coventry, England. derek.egan@keller.co.uk
ABSTRACT: The behaviour of Vibro Replacement stone columns has yet to be
captured fully by analytical or numerical means, and predicting stone column
performance in soft cohesive soils brings specific challenges. In this paper, a new
database of settlement improvement factors is developed, drawn from both published
and unpublished data. The database illustrates that the improvement is generally
predicted quite well by Priebe’s (1995) basic improvement factor. Moreover, the
extent of improvement reflects the construction method, with the preferred dry bottom
feed system performing consistently better than other column construction systems.
INTRODUCTION
Vibro Replacement (VR) has emerged as one of the world’s most widely used forms
of ground improvement in cohesive soils, as solutions may be tailored to meet specific
bearing capacity, settlement magnitude and rate requirements. Mounting pressure
nowadays to develop ‘marginal’ sites has focussed attention on the potential of VR to
offer technically and economically viable solutions in these deposits. There are many
challenges specific to VR in fine soils. Stress changes and ground movement caused
by both the formation of cavities by the poker and the subsequent construction of
compacted columns are poorly understood (Egan et al., 2008). The effect of clay
sensitivity on stone column performance has not been widely researched, and to date
there is no consensus on the extent to which stone columns arrest creep.
The most popular analytical settlement prediction method in European ground
improvement practice (Priebe 1995) contains many simplifying assumptions and some
empiricism in its formulation. Significant advances have been made in developing
constitutive models for soft natural soils for use in conjunction with finite element
software to incorporate characteristics such as creep, anisotropy, destructuration and
bonding (i.e. Karstunen et al., 2005, Leoni et al., 2008). However, industry
practitioners in ground improvement design do not routinely use these models and, in
general, finite element approaches are currently limited by their inability to capture
installation effects satisfactorily, especially the 3-D formulations.
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2. In light of these uncertainties, it was beneficial to carry out a detailed review of
stone column field settlement performance records. A new database of settlement
improvement factors for soft cohesive deposits is presented and interpreted herein. The
discussion considers the operational friction angle of the stone and the effect of the
column construction method, and provides a useful reference for practitioners
designing ground improvement schemes in compressible deposits.
STONE COLUMN CONSTRUCTION METHODS
A brief explanation of the main VR systems is given below, where the terms top-feed
or bottom-feed describe the stone supply method, and wet or dry relates to the jetting
medium. The appropriate choice of construction method and proper on-site
implementation is paramount to the successful improvement of soft and very soft soils.
(i) Dry top feed is predominantly used for shallow to medium treatment depths of
coarse and more competent cohesive deposits. The hole formed by the first penetration
of the poker remains stable as the column is constructed. Controlled air flush is often
used to aid construction and while commonly used for lightly-loaded to heavily-loaded
developments, it is rarely suitable for use in soft cohesive soils.
(ii) Wet top feed is used for medium to deep treatment below the water table and
treatment of softer cohesive deposits. In cohesive soils, water flush helps remove
arisings from the void formed by the poker and maintain its stability. While wet top
feed has been used with success in soft cohesive soils (i.e. Munfakh et al., 1983), it is
used less frequently nowadays due to difficulty in disposal of the flush arisings, so it is
often reserved for larger-scale moderately-loaded to highly-loaded developments.
(iii) Dry bottom feed has now largely replaced the wet top feed method since its
inception in the late 1970s and is principally used for treatment of water-bearing and
soft cohesive deposits. Controlled air flush is used to aid construction and maintain
stability of the void formed by the vibrating poker. Now the preferred construction
technique in soft soils, there is compelling evidence (i.e. Wehr, 2006) that the dry
bottom feed method can successfully treat ground having cu values well below the 15-
20 kPa frequently quoted as the lower practical limit of the system’s applicability.
(iv) Alternative construction methods have been used; De Cock and d’Hoore (1994)
describe bottom rammed columns, which have evolved from the classic Franki pile. A
tube is bottom-driven to the required depth. As it is withdrawn, successive charges of
stone are introduced and progressively forced into the surrounding soil by intensive
ramming. This method is neither practical nor economical for soft soils.
SETTLEMENT IMPROVEMENT DATABASE
Absolute and differential settlement criteria normally govern the design of stone
columns in compressible soils. The authors have compiled a new database with
settlement information from over 20 case histories in cohesive or predominantly
cohesive soils. While the majority of these cases relate to loading of areas that are
wide in relation to the stone column length (subsequently referred to as widespread
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3. loading), three of the cases relate to footings supported by small column groups.
A settlement improvement factor (n) is used to quantity the degree of treatment, and
is defined as:
treated
untreated
s
s
n = [1]
where streated and suntreated are the settlements with and without stone columns
respectively for a particular loaded zone. The database necessarily comprises two
categories of data, distinguished as follows:
(i) Cases where streated and a reference value of suntreated have both been measured, so
the value of n is entirely measurement-based (Table 1).
(ii) Cases where streated values have been measured; however suntreated values have not
been measured but instead predicted either analytically or from experience of
measurements in local of similar ground conditions (Table 2). The values of
suntreated used in this paper are those quoted/inferred in the original references.
Priebe (1995) uses the area replacement ratio r =Ac/A to capture the proportion of
ground replaced by stone in an infinite array; Ac is the area of one column and A is the
plan area of the ‘unit cell’ attributed to a single column. The value of r may be
deduced from the column diameter (D) and spacing (s) according to:
2
⎟
⎠
⎞
⎜
⎝
⎛
==
s
D
k
A
A
r c [2]
Table 1. Case histories in which suntreated and streated were measured
Reference and
Site Location
Material
Treated
Avg.Treatment
Depth(m)
Treatment
Configuration
Treatment
Method
Loading
Type
AreaReplacement
Ratio,r
SettlementImpr.
Factor,n
Watts et al. (2000)
Lancashire, U.K.
clay,
ash fill
3.50 L DTF test strip 0.209 1.47
Greenwood (1970)
Bremerhaven, Germany
clay, peat 6.0 TR WTF emb. 0.260 1.63
Munfakh et al. (1983)
New Orleans, U.S.A.
clay ≈20 TR WTF emb. 0.253 1.70
4.35 TR BF emb. 0.075 1.85Cooper and Rose (1999)
Bristol, U.K.
clay
4.35 TR BF emb. 0.146 2.55
Legend: L=linear, TR = triangular, DTF = dry top feed, WTF= wet top feed, BF = bottom
feed, emb. = embankment
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4. Table 2. Case histories with measured streated but predicted suntreated
Reference and
Site Location
Material
Treated
Avg.Treatment
Depth(m)
Treatment
Configuration
Treatment
Method
LoadingType
AreaReplacement
Ratio,r
SettlementImpr.
Factor,n
Venmans (1998) clay
Holendrecht-Abcoude,
Netherlands
5.2 TR BF emb. 0.170 1.67
Greenwood (1991) clay/
siltCanvey Island, U.K.
10.0 TR WTF stg. tank 0.221 2.38
Raju et al. (2004) silt,
fill
13.5
Kajang, Malaysia
SQ WTF
+BF
emb. 0.240 2.60
peaty
clay 8.5 TR BR stg. tank 0.287 3.0
De Cock and D’hoore (1994)
Antwerp, Belgium
Oreye, Belgium silt 11.0 TR BR stg. tank 0.227 1.83
Baumann and Bauer (1974)
Konstanz, Germany silt 5.5 TR WTF raft 0.472 4.03
silt 6.1 TR WTF stg. tank 0.296 2.80
silt 6.1 TR WTF stg. tank 0.296 3.43
Watt et al. (1974)
Teesport 104, U.K.
Teesport 165, U.K.
Hedon, U.K. clay 6.7 TR WTF stg. tank 0.269 2.77
Greenwood (1974)
Stanlow, U.K. WTF stg. tank 0.309 5.47
silt,
fill 17.0 SQ BF emb. 0.350 4.0
Raju (1997)
Kinrara, Malaysia
Kebun, Malaysia clay 15.0 SQ BF emb. 0.196 2.5
0.086 1.38
0.055 1.24
Bell (1993)
Stockton, U.K.
clay 4.4 TR WTF emb.
0.038 1.15
Kirsch (1979)
Essen, Germany
silt 5.0 STQ WTF stg. tank 0.345 2.35
clay/
silt 7.1 SQ BF pad 0.070 1.94
Kirsch (unpublished)
Berlin-B’burg B, Germany
Berlin-B’burg C, Germany clay/
silt
6.8 SQ BF pad 0.130 2.1
Keller Foundations (unpubl.)
Contract ‘B’, Scotland
clay 5.5 L BF test strip 0.226 1.2
Goughnour and Bayuk
(1979) Hampton, U.S.A.
silt,
clay
6.4 TR WTF emb. 0.339 2.4
Legend: TR = triangular, SQ=square, STQ = staggered square, L=linear, WTF= wet top feed,
BF = bottom feed, BR = bottom rammed, emb. = embankment, stg. tank = storage tank.
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5. where k is π/4 and π/2√3 for square and triangular column grids respectively. Values
of r are also given in Tables 1 and 2, with Ac either measured directly or deduced from
stone consumption records. Values of n (Tables 1 and 2) are plotted against r in Figure
1 for the widespread loading cases. In order to provide a frame of reference for the
data, Figure 1 also includes Priebe’s (1995) basic improvement factor n0 predictions
(eqn 3; assuming Poisson’s ratio of the soil νs=0.33 as is customary) adopting three
different operational friction angles of φ’=350
, φ’=400
and φ’=450
for the stone.
⎥
⎥
⎥
⎦
⎤
⎢
⎢
⎢
⎣
⎡
−
−−
−
+= 1
)
2
'
45(tan)1(4
5
1
2
0
φ
r
r
rn [3]
Case-specific values of φ’ are generally not presented in the literature. Herle et al.
(2008) advise that φ’≈400
is conventionally adopted used in European design practice,
and this would be especially true for soft soils. Additional parameters needed for
predicting Priebe’s (1995) n1 and n2 factors (amendments to n0 to account for column
compressibility and soil and column unit weights respectively) are not available.
Predicted values of n (npred) are plotted against measured (nmeas) values in Figure 2.
Tests plotting below the npred = nmeas line denote measurements which exceed
predictions. Much of the data in Figure 2 is taken from Figure 1 (i.e. npred is n0 based
on φ’=400
). However, Figure 5 also incorporates data from two test strips (Watts et al.,
2001 and Keller Foundations Contract B, unpublished) and two pad footings (Kirsch,
unpublished). The Priebe (1995) correction was applied to npred for the strips to allow
for the reduced efficiency of small groups. No such correction was applied for the pads
as the loaded columns underneath the footings were surrounded by ‘buttressing’
columns, so ‘unit cell’ conditions were assumed for the loaded columns. In Figure 2,
Table 1 (true n measurements, filled symbols) and Table 2 data (open symbols) are
differentiated, and the different systems used to construct the columns are highlighted.
DISCUSSION
Although some scatter is evident, eqn. [3] with φ’=400
provides a good ‘average’
match to all the measured n-r data in Figure 1. This result is in spite of the fact that
there is not enough resolution in the published data to take account of all of the factors
that could have influenced the degree of settlement control. Although difficult to
quantify, an experienced designer would need to account of the following:
(i) uncertainty in the ‘as-constructed’ column diameter and spacing
(ii) the time elapsed since loading at which n is measured is not consistent
throughout all of the case studies. Due to the drainage effect of stone columns,
primary settlement will occur at a faster rate for treated areas than for similarly
loaded untreated areas. If the settlement of the untreated area is measured before
primary settlement is complete, misleadingly low n values will be obtained.
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6. 1
2
3
4
5
6
0 0.1 0.2 0.3 0.4 0.5
Area Replacement Ratio, r = Ac/A
SettlementImprovementFactor,n
Venmans (1998)
Cooper and Rose (1999)
Munfakh et al (1983)
Greenwood (1991)
Raju et al (2004)
De Cock and d'Hoore (1994)
Greenwood (1970)
Baumann and Bauer (1974)
Watt et al (1967)
Greenwood (1974)
Goughnour and Bayuk (1979)
Raju (1997)
Bell (1993)
Kirsch (1979)
Priebe's (1995)
n0 curves, ν = ⅓
φ'=450
φ'=400
φ'=35
0
FIG. 1. Settlement improvement factor against area replacement ratio
for sites with widespread loading
1
2
3
4
5
6
1 2 3 4 5 6
nmeas
npred(Priebe'sn0,withφ'=40
0
)
Bottom Feed [Table 1]
Bottom Feed [Table 2]
Bottom Rammed [Table 2]
Dry Top Feed [Table 1]
Wet Top Feed [Table 1]
Wet Top Feed [Table 2]
npred = nmeas
s
p
npred > nmeas
s
p
s = strip footing
p = pad footing
npred < nmeas
FIG. 2. Predicted versus measured settlement improvement factors
(all sites: widespread loading and footings) distinguished by construction method
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7. (iii) the relative contributions to surface settlement from compression over the depth
of the treated zone and below the treated zone. It is rarely possible to separate
the settlement solely arising from the treated zone in studies carried out on
construction projects, hence in such situations the improvement attributed to the
installation of the stone columns would probably be underestimated.
(iv) variations in the prediction methods used to determine the n values in Table 2.
Figure 2 implies that a design friction angle of φ’=400
may not always give safe
settlement predictions for the top feed system, but as already stated, there may be other
possible variables besides the friction angle. For example, the deposits within the
treatment zone at Bremerhaven (Greenwood, 1970) incorporated some peaty material.
Importantly, the higher nmeas/npred ratios in Figure 2 tend to relate to bottom feed
projects, endorsing the use of this system for delivering consistent settlement
improvement in soft ground conditions. In these cases, it appears appropriate to adopt
a higher friction angle in the range φ’= 40-450
in conjunction with Priebe (1995). Herle
et al. (2008) advocate the use of higher φ’ values (i.e. in excess of 500
), but these are
based on shear box tests carried out on stone at high relative density and not with soft
soil in mind. Good design practice should consider the degree of stone compaction and
the confining strength of the soil, best understood from rig instrumentation.
CONCLUSIONS
The Priebe (2005) design method with conventionally adopted friction angles of 400
provides a conservative estimate of the actual performance of the bottom feed system
in practice. This method, which continues to be the favoured approach for leading
stone column designers, is proved to be reliable even though it does not capture all of
the fundamental soil and stress changes that take place during column construction and
subsequent loading. More sophisticated approaches, such as finite element analysis,
for example, provide another useful tool to geotechnical engineers, although they have
not evolved to a stage of readiness for routine design.
The vast majority of published data pertains to large loaded areas and not to strip or
pad footings. There remains a need for high quality instrumented field tests to improve
our understanding of the factors controlling stone column settlement behaviour.
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Bell, A.L. (1993) Report on performance of vibro replacement ground improvement
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Cooper, M.R. and Rose, A.N. (1999), Stone column support for an embankment on
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