Chapter 1 Introduction 1.1 Background 1.2 Recent developments 1.2.1 Critical condition 1.2.2 Model test 1.2.3 Numerical model 1.3 Key problems 1.4 Key contents Chapter 2 Test system and method 2.1 Introduction 2.2 Erosion-seepage-stress coupling test system 2.2.1 Test apparatus 2.2.2 Soil specimen preparation 2.2.3 Test procedure 2.3 Inclined seepage test system 2.3.1 Test apparatus 2.3.2 Soil specimen preparation 2.3.3 Test procedure 2.4 Particle migration test system 2.4.1 Test apparatus 2.4.2 Soil specimen preparation 2.4.3 Test procedure 2.5 Velocity-direction detection system 2.5.1 Test apparatus 2.5.2 Test procedure 2.6 Meso-test system of hydraulic erosion based on dual light source PIV/PTV 2.6.1 Test apparatus 2.6.2 Soil specimen preparation 2.6.3 Test procedure 2.7 Summary Chapter 3 Seepage failure characteristics of gap-graded soil 3.1 Introduction 3.2 Experimental design scheme 3.3 Influencing factors of erosion in gap-graded soil 3.3.1 Critical hydraulic gradient 3.3.2 PSDs 3.3.3 Dry density 3.3.4 Summary and analysis 3.4 Erosion characteristics of gap-graded soil under complex stress 3.4.1 Suffusion processes of gap-graded soil 3.4.2 Erosion characteristics of gap-graded soil 3.4.3 Volume change law of gap-graded soil 3.4.4 Summary and analysis 3.5 Seepage characteristics of gap-graded soil under complex stress 3.5.1 Seepage velocity 3.5.2 Critical hydraulic gradient 3.5.3 Stress states 3.5.4 Summary and analysis 3.6 Influence of seepage direction on piping development of gap-graded soil 3.7 Summary
Chapter 4 Characteristics of erosion-seepage-stress coupling in piping of gap-graded soil 4.1 Introduction 4.2 Intensity variation in piping process of gap-graded soil 4.2.1 Effect of stress state on erosion-strength 4.2.2 Effect of particle size on erosion-strength 4.2.3 Effect of compactness on erosion-strength 4.3 Coupling law of erosion intensity and stress state of gap-graded soil 4.4 Summary Chapter 5 Mathematical model 5.1 Introduction 5.2 Establishment of piping two-fluid model 5.2.1 Parameter definition 5.2.2 Continuity equation 5.2.3 Equation of motion 5.2.4 Fluid-structure coupling function 5.3 Solution of piping two-fluid model 5.3.1 Fundamentals of Finite Volume Method 5.3.2 Solution of liquid phase motion 5.3.3 Solving solid phase motion 5.3.4 Boundary processing and solution 5.4 An auto-adaptive moving mesh method 5.4.1 Resume 5.4.2 FM generating 5.4.3 Discretization of governing PDE 5.4.4 Erosion law and parameters updating 5.4.5 Stepwise solving of the coupled equations 5.5 Summary Chapter 6 Backward erosion piping in heterogeneous fields 6.1 Introduction 6.2 Synthetic heterogeneous field 6.2.1 Study domain 6.2.2 Random fields 6.2.3 Generating random fields 6.2.4 Realization of random fields 6.3 Solution of the BEP simulation 6.4 Effects of spatial variability 6.4.1 Monte-Carlo simulation 6.4.2 Results of Monte-Carlo simulations 6.5 Mechanism of heterogeneity effects on seepage instability 6.6 Application of seepage instability evaluation 6.7 Summary References
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