.........Slope stability.........

Prepared By:-

Name :- Riyaz Ahmad Bhat;

Email Id: (bhatriyaz1@gmail.com) Department of civil engineering and technology   Course:- B.Tech. , Section :- C;

System Id : (2012018157);

Roll No.:- (120107192);

Submitted to: Professor, Mr. Gaurav Goel.

1.Abstract Despite of our improvement in recognition ,

prediction and mitigative measures, Landslides still have social, economic and environmental toll in mountainous regions. This is partly due to the complexity of the processes driving slopes failures and our inadequate knowledge of the underlying mechanisms. Ever increasingly, Experts are called upon to analyze and predict the stability of the given slope , assessing its risk, potential failure mechanisms, and velocities , areas endangered, and possible remedial measures.

Slope Stability analysis and the purpose These Notes includes the field of Slope Stabilty

analysis and the purpose such analysis serve in investigation of potential slope failure mechanism. Advancements in and the evolution in computer based analysis techniques are discussed, first with respect to commonly applied conventional methods .The determination of kinematics for several common modes of failure are presented in addition to the corresponding analytical and limit equilibrium for factors against slope failure.

….continued

The main objective of the slope stability Analysis has been discussed here.

Slope stability analysis before the computer age and now in the computer era has been discussed in detail. There are various softwares/ programmes used for slope stability purpose. Concept of Hybrid coupled modeling is being also included.

Numerical modeling methods and their application to rock slope stability analysis has been introduced briefly. Yet it must be emphasized that numerical is a tool and not a substitute for critical thinking and judgment. As such, numerical modeling is most effective when by an experienced and cautious user.

2).Introduction: A slope may be an unsupported or supported, inclined surface of some mass like soil mass. Slopes can be natural or man made. These may be above ground level as embankments or below

ground level as cuttings. SLOPE STABILITY In naturally occurring slopes like along hill slopes and river sides, the forces of gravity tends to move soil from high levels to low levels and the forces that resist this action are on account of the shear strength of the soil.

Presence of water increases weight and reduces shear strength and hence decreases stability.

Weights of man made structures constructed on or near slopes tend to increase the destabilizing forces and slope instability.

Causes of failure of Slopes:The important factors that cause instability in

slope and lead to failure are 1. Gravitational force. 2. Force due to seepage of water. 3. Erosion of the surface of slope due to

flowing water. 4. The sudden lowering of water adjacent to

the slope. 5. Forces due to earthquakes.  

3) ExplanationSlope Stability Analysis Slope stability analysis is performed to

assess the safe design of a human-made or natural slopes (e.g. embankments, road cuts, open-pit mining, excavations, landfills etc.) and the equilibrium conditions.

Definition: The term slope stability may be defined as the resistance of inclined surface to failure by sliding or collapsing

The main objectives of slope stability analysisThe main objectives of slope stability analysis

are finding endangered areas, investigation of potential failure mechanisms, determination of the slope sensitivity to different triggering mechanisms, designing of optimal slopes with regard to safety, reliability and economics, designing possible remedial measures, e.g. barriers and stabilization.

continued….Successful design of the slope requires

geological information and site characteristics, e.g. properties of soil/rock mass, slope geometry, groundwater conditions, alternation of materials by faulting, joint or discontinuity systems, movements and tension in joints, earthquake activity etc. Choice of correct analysis technique depends on both site conditions and the potential mode of failure, with careful consideration being given to the varying strengths, weaknesses and limitations inherent in each methodology.

Before the computer agestability analysis was performed graphically

or using hand-held calculator. Today engineers have a lot of

possibilities to use analysis software, ranges from simple limit equilibrium techniques through computational limit analysis approaches (e.g. Finite element limit analysis, Discontinuity layout optimization) to complex and sophisticated numerical solutions (finite-/distinct-element codes).

continued….The engineer must fully understand limitations of each

technique. For example, limit equilibrium is most commonly used and simple solution method, but it can become inadequate if the slope fails by complex mechanisms (e.g. internal deformation and brittle fracture, progressive creep, liquefaction of weaker soil layers, etc.). In these cases more sophisticated numerical modelling techniques should be utilised. In addition, the use of the risk assessment concept is increasing today. Risk assessment is concerned with both the consequence of slope failure and the probability of failure (both require an understanding of the failure mechanism).

continued….Within the last decade (2003) Slope Stability Radar has been developed to remotely scan a rock slope to monitor the spatial deformation of the face. Small movements of a rough wall can be detected with sub-millimeter accuracy by using inter-ferometry techniques

Conventional methods of analysis:Most of the slope stability analysis

computer programs are based on the limit equilibrium concept for a two- or three-dimensional model. In rock slope stability analysis conventional methods can be divided into three groups: kinematic analysis, limit equilibrium and rock fall simulators.

Numerical methods of analysisNumerical modelling techniques provide an approximate solution to problems which otherwise cannot be solved by conventional methods, e.g. complex geometry, material anisotropy, non-linear behaviour, in situ stresses. Numerical analysis allows for material deformation and failure, modelling of pore pressures, creep deformation, dynamic loading, assessing effects of parameter variations etc. However, numerical modelling is restricted by some limitations. For example, input parameters are not usually measured and availability of these data is generally poor. Analysis must be executed by well trained user with good modelling practise. User also should be aware of boundary effects, meshing errors, hardware memory and time restrictions. Numerical methods used for slope stability analysis can be divided into three main groups: continuum, discontinuum and hybrid modelling.

• Hybrid/coupled modelling

Hybrid codes involve the coupling of various methodologies to maximize their key advantages, e.g. limit equilibrium analysis combined with finite element groundwater flow and stress analysis adopted in the SVOFFICE or GEO-STUDIO suites of software; coupled particle flow and finite-difference analyses used in PF3D and FLAC3D. Hybrid techniques allows investigation of piping slope failures and the influence of high groundwater pressures on the failure of weak rock slope. Coupled finite-/distinct-element codes, e.g. ELFEN, provide for the modelling of both intact rock behaviour and the development and behaviour of fractures.

>> Work Done << :- Watched Videos and Images:- During the study of paper, I

watched Almost all related Videos and Images which helped me in understanding the main Objective Of studying Stabilty of Slope analysis. These videos helped me to know the work done on slope stabilty and future plannings done, and helped me to go further steps.

Visited to Kashmir mountain slopes

The slopes of western Lesser Himalaya (at Sangaldhan Block of Udhampur near Ramban, Jammu and Kashmir India) are being severely affected by tectonic and erosional activities. These activities result in deposit of a thick cover of rock fragments and overburden just above the hard rock. The thickness of overburden cover has directly affected the stability of slope in the study area, though the traditional stability estimation techniques, rock mass rating and slope mass rating, rate this area as moderately stable which does not represent the real stability condition. 

Visit to Areas effected byEarth-quake on 08th october 2005 of Muzaffar-abad KashmirThe Mw=7.6 Kashmir Earthquake occurred

on 8th October 2005 as a result of rupture on the NW-SE orientated Muzaffar-abad fault. The hypocenter was located at a depth of about 20 km about 19 km NE of Muzaffarabad in the Neelum River valley. The fault rupture extends for a total distance of about 200 km. The earthquake resulted in widespread destruction over 28,000 km2. The official death toll is 87,300, with landslides being responsible for about 20,000 fatalities .

6) CONCLUSION At the conclusion of this paper we are able to

conclude following objectives:Understand the basic concept of slope stability

analysis;Understand the basic design considerations;Be familiar with slope stability analysis and design

procedure;Know how to verify computer analyses and results;Be able to perform simple slope stability analysis; andBe able to present the analysis and results effectively.

Thanks