1、Groundwater can flow into tunnels through intact materials, joints and fissures, as wellas faults and karst conduits.The mechanical mechanism and evolutionary process ofwater inrush through faults and karst conduits have

2、 been investigated systematically inthe present study using a literature review, theoretical analysis, software development,experimental testing and numerical simulation.The MATLAB platform was used forsoftware package d

3、evelopment, and the PFC3D software was used for numericalsimulation analysis.
　　(1) A novel research method is proposed for the analysis of the internal instabilityof granular soils to identify which type of water inr

4、ush will occur.To verify thefeasibility and accuracy of the novel method, four unimodal parametric PSD modelsand one bimodal parametric PSD model are compared, and dozens of soil specimensare studied.To determine the opt

5、imal parameter values of the PSD models, a softwarepackage termed Analysis Software for Internal Stability of Granular Soils (ASISGS) isdeveloped, which can also obtain the secant slope curves of soil PSDs automatically.

6、Anew synthetic chart is proposed for the analysis of the internal instability of granularsoils, and the evaluation results are in good agreement with experimental tests.
　　(2) The microscopic mechanisms of suffusion i

7、nitiation and development arerevealed.The theoretical formulas and models previously proposed for determining thecritical hydraulic condition of suffusion initiation are compared first, and then a newformula and a new th

8、eoretical model are proposed based on the seepage force and thevariable section capillary model, respectively.For calculation and comparison of theseformulas and theoretical models, a software package termed Calculation

9、Program forCritical Hydraulic Gradient (CPCHG) is developed.The force condition and equilibriumstate of coarse particles under seepage flow are studied and expressed in mathematicalterms, and the critical hydraulic gradi

10、ent of soil skeleton deformation is proposed.
　　(3) An experimental testing apparatus is developed for systematic research on theseepage failure of filling materials in faults and karst conduits subjected to seepage f

11、low.The apparatus comprises an axial load application system, a pressurized water supplysystem, a permeameter cell, a particle collection system, a water collection system anda data acquisition system.A series of experim

12、ents on internally-unstable granular soilswith and without different clay contents, respectively, was conducted under differentaxial stresses.The variations of flow rate and hydraulic conductivity with the hydraulicgradi

13、ent under different conditions are analyzed.The effects of axial stress and claycontent on the evolutionary process and the critical hydraulic condition are investigated,and the typical evolutionary process and phenomena

14、 of seepage failure are summarized.
　　(4) The mesoscopic evolutionary process of seepage failure of non-cohesive fillingmaterials under unidirectional seepage flow is reproduced by seeondary developmentof the PFC3D so

15、ftware.The effect of seepage direction on the evolutionary process ofseepage failure is studied by doing numerical simulations under different seepagedirections.The variations of porosity and flow rate with increasing hy

16、draulic gradientare monitored, as well as the migration pathways of fine particles.Numerous basicscaling relationships and their limitations for a DEM scale model are summarized first,and then a new set of scaling relati

17、onship is proposed using a governing equationapproach for the DEM simulation of fluid-solid coupling problems, and numericalsimulations of the seepage failure with different scaling relationships indicate that it ismore

18、reasonable and accurate than other scaling relationships.
　　(5) Several factors are selected as evaluation indices for risk assessment of waterinrush, and two evaluation index systems used in the design and constructi

19、on stages,respectively, are established.An innovative and effective method named AttributeInterval Evaluation Theory (AIET) is proposed for risk assessment of water inrush.TheAIET can not only quantitatively prioritize r

20、isks by combining consequences andprobability of occurrence, but also analyze the reliability of the evaluation results.Sincethe AIET method is subjected to a large amount of calculations, a practical softwaretermed AIET