Landslides occur when masses of rock, earth, or debris move down a slope. They are caused by a combination of factors that increase shear stress or decrease shear strength, such as heavy rainfall, earthquakes, erosion, and human activity. Landslides can be classified based on material, type of movement, speed, and other attributes. Common types include rotational slides, translational slides, rock falls, debris flows, and soil creeps. Landslides pose risks to infrastructure, property, and human life. The hilly regions of Bangladesh are particularly vulnerable due to factors like deforestation, construction activity, and heavy monsoon rains.
After attending this lesson, the user would be able to understand the nature and causative factors of landslides, their characteristics, classifications, triggering mechanisms, and effects. The methods of controlling the effects of landslides, and avoiding their menace are also highlighted. Disaster management methods are to be adopted to mitigate the never ending natural hazards. This lesson is an important topic in disaster management.
After attending this lesson, the user would be able to understand the nature and causative factors of landslides, their characteristics, classifications, triggering mechanisms, and effects. The methods of controlling the effects of landslides, and avoiding their menace are also highlighted. Disaster management methods are to be adopted to mitigate the never ending natural hazards. This lesson is an important topic in disaster management.
It is refers to the downward sliding of huge quantities of land mass
Downward movement of slope forming material composed of rocks and soil or combination of all these material along surfaces of separation by FALLING, SLIDING AND FLOWING either sudden or slow from one place to another place.
Geomorphology at a glance: Major landformsP.K. Mani
Geomorphology, Major landforms, Genetic landform classifications, Volcanic landforms, River Systems and Fluvial Landforms, Aeolian Landforms, Glacial Landforms
It is refers to the downward sliding of huge quantities of land mass
Downward movement of slope forming material composed of rocks and soil or combination of all these material along surfaces of separation by FALLING, SLIDING AND FLOWING either sudden or slow from one place to another place.
Geomorphology at a glance: Major landformsP.K. Mani
Geomorphology, Major landforms, Genetic landform classifications, Volcanic landforms, River Systems and Fluvial Landforms, Aeolian Landforms, Glacial Landforms
A landslide, also known as a landslip or Mudslide, is a form of mass wasting that includes a wide range of ground movements, such as rockfalls, deep failure of slopes, and shallow debris flows. Landslides can occur underwater, called a submarine landslide, coastal and onshore environments.
Definition, classification & types of landslideTarikIslam9
General Information about Bangladesh
Bangladesh is consisted of a total land area of 147570 km² with hilly areas of 17,342 km² (8.5% of total area of Bangladesh).
Chattagram Hill tracts is the wide ranging hilly area in the southeastern part of the country. Rangamati, Bandarban and Khagrachari are three unique geographical and cultural landscape administrative districts in this region.
Landslides are a common hazard in the Chittagong Hill Districts (CHD) of Bangladesh. The communities that live on dangerous hill slopes in CHD repeatedly experience landslide hazards during the monsoon season, with casualties, economic losses and property damage.
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.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Forklift Classes Overview by Intella PartsIntella Parts
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
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Author: Robbie Edward Sayers
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Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
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Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
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Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
2. Landslides
A landslide is the movement of
rock, debris or earth down a slope.
It results from the failure of the
materials which make up the hill
slope and are driven by the force of
gravity. Landslides are known also
as landslips, slumps or slope
failure.
3. • When, shear stress exceeds
shear strength of the material,
downward movement of rock
materials or debris or soil start
along the slope. Such
movement is called landslide.
• They can occur along a slope
where the internal resistance
of the rocks are reduced or
they loose their holding
capacity.
4. Terminologies
In geology, a wide variety of terms have been
used to describe any detached mass of soil,
rock, or debris that moves down a slope mainly
by gravitational forces. The most frequently used
terms are:
Mass movement
Slope movement
Landslide
Mass wasting
Slope failure
6. The factors contributing to an increase of the
shear stress are
• Removal of lateral and underlying support (erosion,
previous slides, road cuts and quarries)
• Increase of load (weight of rain/snow, fills, vegetation)
• Increase of lateral pressures (hydraulic pressure, roots,
crystallization, swelling of clay)
• Transitory stresses (earthquakes, vibrations of trucks,
machinery, blasting)
• Regional tilting (geological movements).
7. Factors related to the decrease of the
material strength are
• Decrease of material strength (weathering, change in
state of consistency)
• Changes in inter-granular forces (pore water pressure,
solution)
• Changes in structure (decrease strength in failure plane,
fracturing due to unloading)
8. Hills which will not slide easily
Rocky hills will not slide.
Sometimes hills have inclined layers of stiff clay, sand &
soft rocks. If the inclination is away from the cut surface,
sliding will be difficult.
Hills with milder slopes (<30°) are safe against sliding.
9. Factor affecting Landslide
Natural Factors Anthropogenic Factors
I. Gravity
II. Geological factors
III. Heavy and prolonged
rainfall
IV. Earthquakes
V. Forest fire
VI. Volcanoes
VII. Waves
I. Inappropriate drainage
system
II. Cutting and deep
excavations on slopes for
buildings, roads, canals &
mining
III. Change in slope use
pattern, deforestation,
agricultural practices on
steep slopes
Many factors contribute to slides including geology,
gravity, weather, groundwater, wave action and human
action. Typically, a landslide occurs when several of
these factors converge
11. Classification of Earth Movements
Earth Flow Landslides Subsidence
Solifluction
Creep
Rapid flows
Rock slides
Rock falls
Debris slide or
slump
Collapse
Plastic flow
All movement of land masses are referred as landslides, but
differ in many respects, therefore all types of landslides are
categorized as Earth Movements. These are categorized as
Earth Movements
12. Landslide Classification
Following factors have been used to classify landslides.
Material (rock and soil type, their structure as well as
geotechnical properties);
Water (wet, dry, saturated);
Climate (tropical, temperate, cold, arid etc.);
Geomorphic attributes (slope forms, weathering,
topographic profile);
Landslide morphology (size, depth, length, height);
Type of movement (fall, slide, flow etc.);
Triggering mechanism (rainfall, earthquake, human
activities etc.).
Speed of movement (slow, high etc.);
13. Landslide Classification
There are many classification schemes for
landslides proposed by different authors like
Sharpe (1938),
Campbell (1951),
Hutchison (1968, 1969, and 1977),
Crozier (1973),
Varnes (1978),
Wieczorek (1984) and
Cruden and Varnes (1996).
17. Two major types of landslides are
1. Rotational landslide: The surface of
rupture is curved concavely upward
(spoon shaped), and the slide
movement is more or less rotational
i.e. a slump.
2. Translational landslide: The mass of
soil and rock moves out or down and
outward with little rotational
movement or backward tilting. Here
material of landslide may range from
loose, unconsolidated soils to
extensive slabs of rock and may
progress over great distances.
18. Lateral Spreads
Often occur on very gentle
slopes and result in nearly
horizontal movement of
earth materials. Lateral
spreads are usually caused
by liquefaction, where
saturated sediments are
transformed from a solid
into a liquefied state, usually
triggered by an earthquake.
19. Topple
Toppling failures are
distinguished by the forward
rotation of a unit or units
about some pivotal point,
below or low in the unit,
under the actions of gravity
and forces exerted by
adjacent units or by fluids in
cracks.
20. Solifluction
The gradual
movement of wet soil
or other material
down a slope,
especially where
frozen subsoil acts
as a barrier to the
percolation of water.
21. Creep
Creep is extremely slow
downward movement of dry
surfacial matter.
Movement of the soil occurs
in regions which are
subjected to freeze-thaw
conditions. The freeze lifts the
particles of soil and rocks and
when there is a thaw, the
particles are set back down,
but not in the same place as
before.
22. Rapid flow
Rapid flow is similar to the
creep, but differ in terms of
speed and depth. It is faster.
Creep is involved upto
shallow depth (app. 1-2 m),
whereas the rapid flow is
involved to greater depth
(app. upto 5 m or more)
24. Slump
A slump is a form of mass wasting that occurs when a
coherent mass of loosely consolidated materials or rock
layers moves a short distance down a slope.
Movement is characterized by sliding along a concave-
upward or planar surface.
25. Rock slides
Rockslides and other types
of slides involve the
displacement of material along
one or more discrete shearing
surfaces.
The sliding can extend
downward and outward along
a broadly planar surface (a
translational slide), or it can be
rotational along a concave-
upward set of shear surfaces
(a slump).
26. Rock falls
A rock fall is a fragment
of rock (a block)
detached by sliding,
toppling, or falling,
that falls along a vertical
or sub-vertical cliff,
proceeds down slope by
bouncing and flying
along ballistic trajectories
or by rolling on talus or
debris slopes,” (Varnes,
1978).
28. General potential causes of landslide
Geological causes
• Weak material
• Sensitive material
• Weathered material
• Sheared material
• Jointed or fissured material
• Adversely oriented mass discontinuity (bedding, schistocity, etc)
• Adversely oriented structural discontinuity (fault, unconformity etc)
• Contrast in permeability
• Contrast in stiffness (stiff, dense material over plastic material)
29. General potential causes of landslide
Morphological causes
• Tectonic or volcanic uplift
• Glacial rebound
• Wave erosion of slope toe
• Fluvial erosion of slope toe
• Glacial erosion of slope toe
• Erosion of lateral margins
• Subterranean erosion (solution, piping)
• Deposition of load on the slope or its crest
• Vegetation removal
30. General potential causes of landslide
Physical causes
• Intense rainfall
• Prolonged exceptional precipitation
• Rapid snow melt
• Rapid drawdown of floods and tides
• Thawing
• Freeze-and-thaw weathering
• Earthquake
• Volcanic eruption
• Shrink and swell weathering
31. General potential causes of landslide
Human causes
• Excavation of the slope or its toe
• Deposition of load on the slope or its crest
• Drawdown (of reservoirs)
• Deforestation
• Irrigation
• Mining
• Artificial vibration
• Water leakage from utilities
32. Triggering of landslides
Landslide triggering mechanism means event
that makes landslide happens.
An external impetus such as intense rainfall,
earthquake, volcanic eruption, storm waves and
rapid stream erosion, human activities are main
triggering mechanism
41. Affects of Landslide
Landslide cause property damage, injury, death and adversely
affect a variety of resources. For example, water supplies,
fisheries, sewage disposal systems, forests, dams, and
roadways can be affected for years after a slide event.
The negative economic effects of landslide include the cost to
repair structures, loss of property value, disruption of
transportation routes, medical costs in the event of injury and
indirect costs such as lost timber and lost fish stocks.
Water availability, quantity and quality can be affected by
landslides. Geotechnical studies and engineering projects to
assess the stabilize potentially dangerous sites can be costly.
Large, infrequent landslides contribute less to personal and
property losses than the smaller, more frequent slides and
debris torrents in populated areas.
43. Physiography of Bangladesh Hills, Land use and
Vulnerabilities
About 82% land of
Bangladesh can be
identified as recent plains
and 18% as terrace and
hilly area.
Pleistocene terrace has
covered 10% and eastern
and north-eastern tertiary
hill are of only 8% of the
country.
44. Physiographically, hilly regions can be divided
into the following three sub-regions:
1. Chittagong and Chittagong Hill Tract
2. Hill Ranges of Northeastern Sylhet
3. Hill along the narrow northern strip of Sylhet
and Mymensingh
45. Landslide Trends in Chittagong
Year Location Consequence
1990 Occurred on May 30, Rangamati district
Affected the link road embankment at Jhagar
beel area.
1997
Occurred in July,
Charaipada of Bandarban
Affected total 90,000-sq m area.
1999
Occurred on August 11, Bandarban
Seven fatalities reported. Affected Lama
Thana and Aziznagar Union.
11 August landslide was followed again
on 15 August at village Chittaputi,
Bandarban
At least 50 houses completely vanished
under the solid earth and 300 houses were
partly damaged. About of cultivated land, of
household garden, and unmetalled road
crushed.
Occurred on August 11 at Gopaipur
under Kotwali Thana
Ten Fatalities reported. Crushed two
thatched house killing the inmates.
2000 Occurred on June 24 at campus and
other parts of
At least Thirteen people died and Twenty
injured.
46. Year Location Consequence
2003 Occurred on June Cox's Bazar Six casualties reported.
Occurred on July 30 due to magnitude 5.9
Earthquake
Six causalities reported.
2006 Occurred in September at village Rajarkol,
Cox’s Bazar
Killed Two children and injured Six.
2007 Occurred in June at Mati Jharna colony of
Lalkhan Bazar,
Killed 128 people, injured 100
2008 Occurred on July 3, at Teknaf and Ukhia
subdistricts of Cox's Bazar
14 people died.
Occurred on July 4 at Cox's Bazar
Two people in one family were buried alive
under mud.
Occurred on July 14 at Himchhari, Cox’s Bazar Killed 2 persons under mudslide.
Occurred on August 11 at Cox’s bazar Killed 3 family members.
Occurred on August 18 at Matijharna of and
Cox's Bazar
Killed at least 14 people, a dozen injured and
10 others feared trapped at Matijharna
2009 1st August at Lama Upazilla, Bandarban Killed 10 people and destroyed 50 houses.
2010 Occurred on 16th June at Cox-Bazar 52 peoples were killed.
47. Causes of these landslides in Chittagong
Hill Cutting: Hills of Chittagong is being cut for building
construction, develop resedential/ housing area, clay and
sand mining and developing road network.
Sandy hill; about 95% of hill soil is sand of which 8.44% is
coarse sand (dia. > 600 microns) & 86.8% is fine sand
(75<dia<600 microns); the remaining 4.76% is silt & clay (dia
<75 microns).
Deforestation: Khulshi, Batali hill and hills near Foy’s lake are
massively affected by deforestation in Chittagong city.
Rainfall: The average yearly rainfall of Chittagong is
approximately 3000mm. More rainfall increases the probability
of landslide.
48. Landslide Vulnerability in Chittagong
Although tertiary hills of
Chittagong are prone to
landslides due to its
formation and structure
but it can be reduced by
stopping hill cutting and
deforestation etc. Risk is
higher where settlement
exists on the foothills
and poor people live
within the areas.
49. Sustainable Management Options
• Landslide vulnerability assessment and zoning
• Strict compliance of zoning and other legal and
policy instruments
• Re-location of the foothill slums
• Proper compliance of existing legal provisions
• Real time monitoring and early warning
• Enhancement of public awareness
• Establishment of the emergency response and
recovery team and facilities
51. Land Subsidence
• Land subsidence is
defined as the lowering of
the land surface.
• Many different factors can
cause the land surface to
subside.
• Subsidence can occur
rapidly due to a sinkhole or
under ground mine
collapse, or during a major
earthquake.
52. How does Land Subsidence occur?
Land subsidence in an environmental hazard
which is caused by overdraft of ground water
or oil extraction and results in gradual setting
or sudden sinking of the earth’s surface owing
to subsurface movement of the materials of
the earth.
Decline of water table or piezometric surface
results in vertical compression of the sub-
surface materials. Along with vertical
compression, lateral compression may also
take place due to initiation or acceleration of
lateral flow of groundwater. This lateral
movement also results in subsidence of the
land surface.
53. Principal causes of Land Subsidence are
1. Aquifer system compaction (extraction of oil, gas, water
beneath the surface)
2. Drainage of organic soils
3. Underground mining
4. Hydro compaction
5. Natural compaction (natural settlement)
6. Sinkholes
7. Thawing permafrost
54. Three distinct process accounts for most of
water related subsidence
—Compaction of aquifer systems
—Drainage & subsequent oxidation of organic
soils
—Dissolution & collapse of susceptible rocks
56. Classification of land subsidence rate
Landslide
rate
(mm/year)
Class
>20 Very high
15-20 high
10-15 Medium
5-10 low
0-5 very low
Dominico’s eqon. (1972)
C = mv. ∆σ. Z. H
Where,
C = amount of land subsidence
(m)
mv = coeff. of volume decrease
(cm2/kg)
∆σ = effective stress per meter
fall of piezometric level (kg/cm2)
Z = drop in piezometric level (m)
H= thickness of cutting bed (m)
57. Effects of Land Subsidence
Land subsidence can have several negative economic and
social implications such as
Changes in ground water & surface water flow patterns
Restriction on pumping in land subsidence-prone areas
Localized flooding
Failure of well casings as well as shearing of structures
Land subsidence impact on the environment can be
Quite noticeable with uneven surface topography & depressions in
earth’s surface.
Affects the wildlife habitat that may or may not return to normal over
time.
Potential to reroute, displace & contaminate groundwater
Altering the immediate land & aquatic ecosystems
Pollute & impact ecosystems with contaminants (hazardous materials,
sewage etc.) being transported throughout the aquifer.
59. Classification of slope
• Natural slope - in various conditions, including rock slope
• Man-made slope
- including cut-back slope or slope formed by filled
material with adequate compaction, usually provided
with surface and surface drainage
- formed mainly with the support by retaining structures
60. Components on a well-design and maintained
man-made slope
1. Surface protection such as vegetation (rigid cover,
masonry, plaster or shotcrete)
2. Surface drainage (including surface channels, catch pits
and sand traps)
3. Subsurface drainage (including weep holes and subsoil
drain etc.)
4. Other protective provision such as pre stressed ground
anchors.
61. How a slope fails?
• Relatively shallow top soil further worsened by the
weathering and infiltration during rainstorms situations.
• Slope can collapse easily by shear if the soil is nearly
saturated and high pore pressure can be built up rapidly.
The falling debris carried by its potential and momentum
can rush down the slope at very high speed and travel a
long distance causing huge damages.
• Highly decomposed rock in a slope may behave very
similar to soil.
62. Factors affecting the stability of slope
1. Topography and its surrounding physical conditions: site
investigation process.
2. Geological conditions such as the nature and depth of its
subsoil, degree of decomposition, or location of fracture
etc: soil investigation.
3. Shear strength of the slope-forming materials: laboratory
tests.
4. Surface and ground water condition
5. External loading and surcharges, such as from traffic,
nearby structures, possible vibration etc.
68. Stability of slope can be effectively improved by the
provision of an appropriately designed drainage
system:
1. A surface drain system that is capable to discharge the entire storm water
within the rain water catchment area affecting the slope in a designated
period of time (say, 200mm rainfall/hour). A surface drain system usually
consists of:
- surface channel
- stepped or trapezoidal channel
- catchpit or sand trap
2. A subsoil drain system that is laid below surface for the discharging of
ground water and to maintain the water pressure be kept in a safe level
- filter layer behind the slope leading water to outlets
- weep holes
- cut-off drain
- subsoil drain pipe
70. Scaling – loose blocks or boulders to be removed from
exposed rock surfaces, this is usually done by manual
method.
Construct buttress support – this is concrete or
masonry gravity structure use to retain the unstable rock
mass
71. Dentition – exposed soft material in a rock face be
trimmed back. The resulting slot be filled with filter
material and protected by masonry or concrete to
prevent erosion.
Sprayed concrete – apply concrete protection to zones
of weak or highly fractured rock faces by spray-on
method.
72. Dowel – a hole is drilled and provide untensioned steel bars,
usually 25mm to 35mm dia. and 1m to 3m long, to stabilize a
weak rock zone. The hole would be grouted afterward.
Rock bolt/nail – this is tensioned bar inserted into rock
forming a short anchorage zone in rock so that an unstable
slope area being reinforced by tension. Typical rock bolts are
25mm to 40mm in dia. 3m to 6m long, and have a tensile
working load around 100kN.
73. Protection to slope by rigid surface
Rigid surface protection on slopes are commonly used to
reduce rainwater infiltration and to prevent erosion of the
slope forming materials. This can be done by:
• Chunam plastering – this is an applied-on surface protection
to slope using a clay and cement mixed plaster. Thickness of
the plaster is around 40mm to 50mm for permanent works.
• Sprayed concrete (shotcrete) – protection by applying a
spraying mortar onto surface of slope.
• Masonry or stone pitching – lay stone rubble or block (with
filter layer underneath) onto surface to protect slope from
weathering
74. Improvement to slope by soft surface
• Hydroseeding – is the application of grass seed mixed
with fertilizer and Nutrient in aqueous solution by
spraying method. The grass seed will grow eventually and
the root of the grass will act as an organic reinforcing
fiber and hold the surface soil.
• Turfing – Turfing is the direct application of grass with
developed roots onto the slope surface. The relatively
matured grass will grow easier and extend its root into
the soil to strengthen the overall surface.
• Planting of tree – usually done at the same time with the
other method to provide better visual result and provide
further strengthening effect to the slope by its deep root.
75.
76.
77. Recommended Protective Measures
Preventive Measure Soil Improvement
i. Providing Rock Anchors,
Providing Soil Anchor;
ii. Providing Soil Nailing;
iii. Providing Compaction Grouting;
iv. Providing Pressure Grouting;
v. Providing Chemical Grouting;
vi. Providing Micro Piles - Mini Piles
vii. Providing Retaining wall;
viii.Use of Geo-grid;
ix. Use of sand piles/sheet pile.
a) Use of Geo-jute – A Bioengineering
Solution to Inhibit Top Soil Erosion
b) Improving drainage quality
c) Changing geometry of hill slope
d) Erosion can be either totally
eliminated or at least significantly
reduced through Vegetation
78. Conclusion
Recommendations to reduce the risk of landslide-
Planting natural vegetations to stabilize the soil from sliding.
Evacuating risky hill toes.
Rehabilitating low income people from the risky hill toes.
Protective measures to avoid landslides during building construction.
Recommendations to reduce the risk of land subsidence-
Proper ground water management should be considered in
subsidence prone areas.
Editor's Notes
Chittagong hills are the part of tertiary hills. The geological structure and soils are weak and also have steep slopes which increase the risk and vulnerability by landslide. The main causes that triggered slope instability induced landslides in Chittagong region of Bangladesh could be summarized as follows:
Hill Cutting: Hills of Chittagong is being cut for building construction, develop resedential/ housing area, clay and sand mining and developing road network. Because of hill cutting, the slopes become instable. The hills of Chittagong were cut with slopes of 70-8- degrees. If rain intensity is too high, minerals of soil dissolve very quickly and the soil turns into mud and becomes very heavy. The steep slope of the hills cannot bear the mass weighof the soil or mud that results the landslide.
Deforestation: Deforestation in the hill areas is another major reason of landslide in Chittagong. Deforested areas are more prone to landslide than a forested area. Vegetation protects the soils and makes slope stable which reduce the risk of landslides. Khulshi, Batali hill and hills near Foy’s lake are massively affected by deforestation in Chittagong city.
Rainfall: The average yearly rainfall of Chittagong is approximately 3000mm. More rainfall increases the probability of landslide. Rainfall causes landslide by lossening the soil compaction and also by increasng the weight of the soils of the hills. Seepage of the rainwater dissolves the limestone and soils of the slopes are converted into clay that moves downward causing landslide.
It is possible to reduce the risk and landslide intensity as well as frequency by adopting the following management options-
Landslide vulnerability assessment and zoning: Landslide vulnerability assessment and zoning
is a prerequisite for sustainable management. Because of the landslide vulnerability varies depending on different types of landuse. On the basis of geomorphologic biological and socio-economic analysis, the zoning should be administered.
Strict compliance of zoning and other legal and policy instruments: City planning, Land use and Utilization must adhere to the recommended land zoning and relevant policy and Legal provisions.
Re-location of the foothill slums: Several large slums are located in different foothills of Chittagong. Most of these are on government-owned lands grabbed by the influential people. The slums are very densely populated and made of bamboo and earthen materials which extremely exposed to the risk of landslide. This risk can be reduced by relocating these slums to safer places.
Proper compliance of existing legal provisions: Landslide related hazards can be reduced or even probability of land sliding can be reduced if only hill cutting could have prohibited. In cases of the places, where hill cutting has already taken place, sustainable structural measures such as retaining wall can be explored as mitigation options.
Real time monitoring and early warning: Most of the landslides in Chittagong city and Chittagong hilly areas happen during the rainy season when rainfall intensity is very high. Therefore rainy seasons need to be monitored closely to assess the situation, especially in the landslide prone area.
Enhancement of public awareness: Comprehensive awareness is to be administered to enhance public awareness about the harmful effects of hill cutting and associated legal restrictions. Awareness program should also contain the significance of proper landuse as well as sustainable land management.
Establishment of the emergency response and recovery team and facilities: A special professional team should be foormed and the fire brigade and police department should be trained up on the emergency rescue and recovery aspects.