Failure Mechanism and Stability Analysis of Rock Slope: New Insight and Methods

263 Pages·2020·15.695 MB·English

by  Ke Zhang

Ke Zhang
Failure Mechanism
and Stability Analysis
of Rock Slope
New Insight and Methods
Failure Mechanism and Stability Analysis of Rock
Slope
Ke Zhang
Failure Mechanism
and Stability Analysis
of Rock Slope
New Insight and Methods
123
Ke Zhang
Faculty of Electric Power Engineering
KunmingUniversity ofScience
andTechnology
Kunming, Yunnan,China
ISBN978-981-15-5742-2 ISBN978-981-15-5743-9 (eBook)
https://doi.org/10.1007/978-981-15-5743-9
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Preface
To cope with the rapid development of China, various slopes have been made in
rock engineering projects. The stability analysis of rock slopes has been a critical
and challenging problem being faced. However, these rock slopes usually contain
various discontinuities of different sizes and shapes that play a dominant role in
theirfailure.Thisbookfocusesonthepre-existinggeologicalstructuresintherock
slopes. Based on the geological conditions encountered, rock slope failure modes
areeitherdrivenbylarge-scale,globalfailuremechanismorstructurallycontrolled
failure mechanism. Using new insights and methods, the failure mechanism and
stability analysis methods of rock slopes are investigated based on a synthesis of
laboratorytesting,theoreticalanalysis,numericalmodelsandpracticalapplications.
This book is based on the research work by the author in the past 10 years,
including11chaptersandthreeparts.Chapter1reviewsthecrackpropagationand
coalescenceinrocks,andnumericalmethodsofrockslopestabilityanalysis.PartI
(Chaps. 2−3) investigates the shear fracturing and fractal behavior of rock bridges
in jointed rock slopes by conducting shear-box experiments, numerial simulations
and fractal analysis. Part II (Chaps. 4−8) conducts a systematical study on the
large-scale,globalfailuremechanismandstabilityanalysisbyusingthekinematical
element method, integrated karst cave stochastic model-limit equilibrium method
and improved strength reduction method. Part III (Chap. 9−11) conducts a sys-
tematical study on the structurally-controlled failure mechanism and stability
analysisbyusingthediscontinuitykinematicalelementmethod,improvedstrength
reduction method and fracture mechanics method.
This book was supported by the National Natural Science Foundation of China
(Grant Nos. 11902128, 41762021), the Applied Basic Research Foundation of
Yunnan Province, China (Grant Nos. 2019FI012, 2018FB093), the Young Elite
ScientistSponsorshipProgrambyCSRME(GrantNo.2016QT-6-6),andtheChina
Postdoctoral Science Foundation (Grant Nos. 2017T100715, 2016M592717).
I would like to express our gratitude to my colleagues, engineering geologists,
geotechnical engineers and mining engineers with whom I have worked all these
years.Iammostgratefultomythreesupervisors,Prof.PingCao,Prof.GuoweiMa,
and Prof. Heming Cheng, for all of their unswerving encouragement and support
v
vi Preface
during my time at Central South University, University of Western Australia and
Kunming UniversityofScience and Technology, respectively. I wouldalso like to
thank them for being a great role model for me in pursuing a scientific career, a
healthy lifestyle and a peaceful mind.
Lastbutnotleast,Iwouldliketogivespecialthankstomyfamilymembers,in
particularmywifeRuiBaoandmydaughterXinyinZhangforbringingmealotof
joyfulness and happiness. Thanks for being with me.
Kunming, Yunnan, China Ke Zhang
March 2020
About This Book
TocopewiththerapiddevelopmentofChina,rockslopestabilityhasbeenamajor
problem faced during construction. This book presents in-depth knowledge of
laboratory experiments, theories, modeling techniques, and practices for the anal-
ysis and design of rock slopes under complicated geological environments. New
conceptsinkinematicalelementmethod,discontinuitykinematicalelementmethod,
integratedkarstcavestochasticmodel-limitequilibriummethod,improvedstrength
reductionmethod,andfracturemechanicsmethodareaddressed,withconsideration
of significant geological features.
The book is intended to be a reference for geotechnical engineering and engi-
neering geology professionals and a textbook for related graduate courses.
vii
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Crack Propagation and Coalescence in Rocks. . . . . . . . . . . . . . 3
1.3 Numerical Methods of Rock Slope Stability Analysis . . . . . . . . 5
1.3.1 Limit Equilibrium Method . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 Numerical Techniques and Strength Reduction
Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.3 Fracture Mechanics Method . . . . . . . . . . . . . . . . . . . . 7
1.4 Main Contents in This Book . . . . . . . . . . . . . . . . . . . . . . . . . . 7
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Part I Experimental Studies on Shear Failure Mechanism
of Rock Masses
2 Influence of Flaw Inclination on Shear Fracturing
and Fractal Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.1 Experimental Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1.1 Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 21
2.1.2 Testing Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.1.3 Physical Implications of Shear-Box Test . . . . . . . . . . . 23
2.2 Patterns of Crack Propagation and Coalescence . . . . . . . . . . . . 23
2.2.1 Tensile Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.2 Shear Cracks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
2.2.3 Coalescence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.3 Peak Shear Strength of Flawed Specimens . . . . . . . . . . . . . . . . 32
2.3.1 Role of Shear-Normal Stress Ratio . . . . . . . . . . . . . . . 32
2.3.2 Role of Flaw Inclination. . . . . . . . . . . . . . . . . . . . . . . 33
ix
x Contents
2.4 Fractal Characteristics of the Fragmentation . . . . . . . . . . . . . . . 34
2.4.1 Sieve Test Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.4.2 Calculation of Fractal Dimension . . . . . . . . . . . . . . . . 34
2.4.3 Results and Discussions . . . . . . . . . . . . . . . . . . . . . . . 35
2.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3 Influence of Flaw Density on Shear Fracturing
and Fractal Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
3.1 Experimental Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.1.1 The 1991 Randa Rockslide and Conceptual
Rock Bridge Model . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.1.2 Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . 43
3.1.3 Experimental Setup and Results . . . . . . . . . . . . . . . . . 45
3.2 Numerical Shear-Box Tests with the RFPA Model . . . . . . . . . . 47
3.3 Shear Fracturing Behavior of Rock Bridges . . . . . . . . . . . . . . . 50
3.3.1 Mechanical Behavior of Crack Initiation . . . . . . . . . . . 52
3.3.2 Mechanical Behavior of Crack Propagation
and Coalescence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3.3 Peak Shear Strength of Specimens. . . . . . . . . . . . . . . . 55
3.3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.4 Fractal Characteristics of the Shear Fracture Surface. . . . . . . . . 59
3.4.1 Digital Image Processing . . . . . . . . . . . . . . . . . . . . . . 59
3.4.2 Box-Counting Fractal Dimension . . . . . . . . . . . . . . . . 60
3.4.3 Results and Discussion. . . . . . . . . . . . . . . . . . . . . . . . 60
3.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Part II Large-Scale, Global Failure Mechanism and Stability
Analysis
4 Empirical Methods for Estimating Strength Parameters of
Jointed Rock Masses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
4.1 Methods Relating Strength with RQD . . . . . . . . . . . . . . . . . . . 70
4.2 Methods Relating Strength with Q. . . . . . . . . . . . . . . . . . . . . . 70
4.3 Methods Relating Strength with RMR . . . . . . . . . . . . . . . . . . . 71
4.4 Methods Relating Strength with Hoek-Brown
Failure Criterion and GSI . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
5 Kinematical Element Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.1 Kinematical Element Formulation Subjected to Seismic
Loading and Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.1.1 Generation and Discretization of a Plastic
Sliding Zone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
Contents xi
5.1.2 Kinematics Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.1.3 Static Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.1.4 Factor of Safety Computation . . . . . . . . . . . . . . . . . . . 80
5.1.5 Optimization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2 Numerical Studies and Verification . . . . . . . . . . . . . . . . . . . . . 81
5.2.1 Example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
5.2.2 Example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.2.3 Example 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.2.4 Influence of Vertical and Inclined Inter-Element
Boundaries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5.3 Blasting Effect on Slope Stability and Example Analysis . . . . . 86
5.4 Seismic Stability Charts for Slopes . . . . . . . . . . . . . . . . . . . . . 88
5.4.1 Seismic Stability Charts for Preliminary Analysis. . . . . 90
5.4.2 Back Analysis Based on Seismic Stability Charts. . . . . 90
5.5 Rigorous Back Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
5.5.1 Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . 97
5.5.2 Back Analysis Procedure . . . . . . . . . . . . . . . . . . . . . . 99
5.5.3 Example Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
5.6 Reliability Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
5.6.1 Theoretical Background . . . . . . . . . . . . . . . . . . . . . . . 105
5.6.2 Example Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
5.7 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
6 Integrated Karst Cave Stochastic Model-Limit Equilibrium
Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
6.1 Engineering Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.1.1 Study Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.1.2 Stratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.1.3 Karst Data Collection . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.2 AMonteCarloSimulationtoGenerateaKarstCaveStochastic
Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.1 General Description . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.2.2 A Stochastic Representation of the Length
of a Karst Cave . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
6.2.3 A Stochastic Representation for the Length
of Carbonatite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
6.2.4 Karst Cave Stochastic Model Generator. . . . . . . . . . . . 122
6.3 Integrated Methodology for Stability Analysis . . . . . . . . . . . . . 124
6.3.1 Stability Analysis Procedure . . . . . . . . . . . . . . . . . . . . 124
6.3.2 Numerical Model of Open Pit Slope . . . . . . . . . . . . . . 125
6.3.3 Results and Discussions . . . . . . . . . . . . . . . . . . . . . . . 129