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Three-dimensional Slope Stability Analysis by Shear Strength Reduction Finite Element Method (SSR-FEM) under Drawdown Condition

Author: WanShaoShi
Tutor: NianTingKai
School: Dalian University of Technology
Course: Geotechnical Engineering
Keywords: slope stability strength reduction finite element method(SSR-FEM) instability criteria critical slip surfaces location water drawdown conditions transient unsaturated seepage phreatic surface three-dimensional slope
CLC: TU43
Type: Master's thesis
Year: 2009
Downloads: 363
Quote: 4
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Executive Summary


More and more attentions have been paid to shear strength reduction finite element method(SSR-FEM) for slope stability analysis.Because it has the advantages as follows:(1) No assumption to be made in advance about the shape of the failure surface;(2) Considered non-linear stress-strain relation on soil;(3) Simulation of progressive failure of slopes.But some problems need to be studied in advance.For example,mesh shape,size and order for the accuracy of the calculation;failure criteria;how to analyze slopes stability by shear strength reduction finite element method(SSR-FEM) under transient unsaturated seepages and whether it is rational that SSR-FEM is extended to 3D slope.They are worthy of further study.The main research work done in this thesis consists of the following parts.1.The effect of mesh shape,size and order on the factor of safety is systematically discussed at first.The effect of mesh on the failure criteria is then studied.When a slope arrives at the critical failure state by SSR-FEM used rational mesh shape,size and order,the four failure criteria as plastic zone extension from the toe to the top of slope,equivalent plastic strain exceeding a certain value developed along the potential slip surface,uncontrollable increase in characteristic nodal displacement on slope surface and the iteration non-convergence of nonlinear FEM numerical calculations can be found in turn.Discussed calculation results which showed the four evaluation criteria are highly consistent.Location of potential slip surface and out-slip point is associated with cohesion,internal friction angle and slope angle. The factors of safety obtained by the limit analysis method and SSR-FEM are compared for various slopes with different slope angle,slope height,cohesion and internal friction angle. Moreover,SSR-FEM is also applied to the stability of slopes under complex conditions.2.The safety factor of slope stability and failure mechanism are systematically discussed under various drawdown condtions.Water drawdown conditions can be divided into three modes as rapid drawdown,slow drawdown,simple transient unsaturated seepage or transient unsaturated seepage.Shear strength reduction finite element method(SSR-FEM) has been applied to analyze the slope stability and failure mechanism under water rapid and slow drawdown,the factors of safety achived are compared with those by the limit analysis method(LAM).The transient unsaturated seepage in soil slope is systematically investigated and the stability of a slope is analyzed by SSR-FEM.Emphases are given to discuss the influence of cohesion,internal friction angle,slope angle,location of phreatic surface,soil permeability,drawdown ratio,drawdown rate and matfic suction subjected to transient unsaturated seepage on the slope stability.And the effect of dilatancy on factors of safety and location of potential slip surfaces is also discussed.3.Shear strength reduction finite element method(SSR-FEM) has been applied to the stability of three-dimensional slopes.For further verification of the present method,a series of 3D analysis has been presented for comparison with results obtained by various investigators using other 3D slope stability techniques.Their results are in good agreement.The factors of safety and location of slip surfaces are associated with slope length/width,boundary conditions, material parameters,geometry dimension,retaining structure.Furthermore,it is compared with the factors of safety of 2D slopes.The 3D SSR-FEM is finally used to analyze the stability of slope under water drawdown con&ion.

Full-text Catalog


Abstract     4-5
Abstract     5-11
1 Introduction     11-23
1.1 Introduction     11-12
1.2 Slope Stability Analysis Method     12-16
1.2.1-side (slide) the definition of the slope stability factor of safety     12-14
1.2.2 Slope stability analysis of the limit equilibrium method     14-16
1.2.3 Strength reduction technique in the development and application of slope stability analysis     16
1.3 Considering Seepage slope stability research status and existing problems     16-18
1.3.1 limit equilibrium method the wading slope stability analysis of the application     17
1.3.2 strength reduction finite element method in slope stability analysis of wading     17-18
1.4 three-dimensional slope stability analysis of the research status and existing problems     18-20
1.5 of this article the main research and technical routes     20-23
1.5.1 In this paper, the main research     20-21
1.5.2 technical route     21-23
2 slope stability analysis of the intensity reduction of the elastic-plastic finite element numerical analysis method     23-55
2.1 Introduction     23
2.2 calculation methods and numerical implementation     23-30
2.2.1 finite element analysis software ABAQUS     23-24
2.2.2 computational model     24-30
the
2.2.3 intensity is reduction technique     30
2.3 finite element mesh to calculate the safety factor of slope stability     30-41
2.3.1 mesh density and element order impact     30-39
2.3.2 relative to the grid size     39-41
2.4 unit type and size of the instability criterion is the appropriateness of     41-44
2.4.1 quadrilateral first order unit     41
2.4.2 quadrilateral second-order unit     41-42
2.4.3 triangular second-order unit     42-43
2.4.4 four kinds of instability criterion of contact and contrast     43-44
2.5 slope failure mode and effect factor analysis     44-47
2.5.1 the location of the critical slip surface angle of internal friction     44-45
2.5.2 cohesion of the location of the critical slip surface     45-46
2.5.3 slope The angle on the critical slip surface location     46-47
2.6 calculation accuracy compared     47-48
2.7 complex slope stability analysis     48-54
2.7.1 into layers slope stability analysis     48-50
2.7.2 of the complexity of soil slope stability analysis     50-51
2.7.3 with weak interlayer purely cohesive soil slope stability analysis     51-53
2.7.4 Multi-level slope stability analysis     53-54
2.8 Conclusion     54-55
3 three kinds of water level decline in the mode of slope stability strength reduction finite element analysis     55-86
3.1 Introduction     55-56
3.2 unsaturated - the theoretical basis and numerical implementation of the slope stability analysis under unsteady flow conditions     56-58
3.2.1 unsaturated - non-steady seepage analysis     56
3.2.2 consider the influence of matric suction strength reduction technique     56-57
3.2.3 slope stability strength reduction finite element method numerical implementation of the method     57-58
3.3 flow of solid coupled finite element calculation of the theoretical basis and numerical implementation     58-60
3.3.1 consider the hydrostatic pressure of the porous medium static equilibrium equations     58
3.3.2 continuity equation     58-59
3.3.3 Finite element calculation     59
3.3.4 ABAQUS finite element numerical implementation     59-60
3.4 drawdown gentle slope stability analysis in the mode     60-65
3.4.1 of water level decline of three modes     60-61
3.4.2 drawdown and slow down under the conditions of slope stability analysis     61
3.4.3 drawdown and slow down the slope under the conditions of example analysis     61-62
3.4.4 libraries water level slow down the conditions, slope stability analysis     62-63
3.4.5 library rapid drawdown conditions, slope stability analysis     63-64
3.4.6 library drawdown and slow down under the conditions of slope safety factor contrast     64-65
3.5 simplify the non-saturated - unsteady flow conditions, slope stability analysis     65-66
3.6 non-saturated - unsteady flow conditions, slope stability analysis     66-72
3.6.1 a slope line of the final infiltration     67-68
3.6.2 permeability coefficient on the slope safety factor     68-69
3.6.3 water level decline in the rate of slope safety factor     69-71
3.6.4 drawdown than the slope safety factor     71-72
3.6.5 consider the matric suction on slope stability analysis     72
3.7 chart in wading slope     72-81
3.7.1 different conditions, infiltration line distribution     73-77
3.7.2 safety coefficient diagram method     77-81
3.8 dilatancy slope stability in the three drawdown mode     81-84
3.8.1 dilatancy stability of slopes under conditions of the drawdown gentle drop     81-82
3.8.2 dilatancy simplify the impact of the conditions of saturation line     82-83
3.8.3 dilatancy in the non-saturated - unsteady flow conditions for Slope Stability     83-84
3.9 Conclusion     84-86
4 three-dimensional the wading slope stability strength reduction finite element analysis     86-121
4.1 Introduction     86
4.2 basic questions     86-87
4.2.1 boundary conditions     86-87
4.2.2 slope instability criterion     87
4.3 3D slope stability analysis and comparative analysis of two-dimensional stable     87-90
4.4 typical example checking     90-95
4.3.1 classic example of a     90-92
4.3.2 classic example     92-95
4.4 soil material parameters on the three-dimensional slope stability     95-100
friction angle with the boundary conditions on the safety factor
4.4.1     96-97
friction angle and the boundary conditions
4.4.2 sliding surface     97-100
4.5 slope of the geometry of three-dimensional slope stability     100-114
4.5.1 corner     100-106
4.5.2 slope is     106-111
4.5.3 corner arc shape of     111-114
4.6 retaining structure     114-118
4.6.1 reinforced with piles of two-dimensional slope     114-115
4.6.2 reinforced with piles three-dimensional slope     115-118
4.7 wading three-dimensional slope stability     118-120
4.8 Conclusion     120-121
5 Conclusions and Outlook     121-124
5.1 Conclusion     121-123
5.2 Looking     123-124
References     124-130
master's degree during the academic situation     130-131
thank     131-132

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CLC: > Industrial Technology > Building Science > Soil mechanics,foundation engineering > Soil Mechanics
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