Research On Catastrophe Mechanism And Slope Stability Under The Disaster Environment

China is a disaster-prone country, and most of disasters are related to slopes, such as landslides, mountain collapse, drop stones, debris flow and so on. They are all the global natural catastrophes with immediate damages on people’s lives and properties, so the catastrophic mechanism and the slope stability evaluation are being the focus researches at home and abroad. Due to the diversity of geology, hydrology and load conditions, slope engineering is under a complex disaster environment and the slope failure is a systemic, complex problem with many uncertainties and dynamic characteristics. This paper has mainly discussed several special problems of slope engineerings in complicated geological conditions, the disaster factors of rainfall and water level variations in the hazard environment. To reveal the general rules of slope disasters, failure mechanism and stability characteristics of the typical slope structure have been investigated under the different disaster factors. The main contents and results are as follows:(1) The influence factors of slope disasters, instability modes and mechanical mechanisms of catastrophe are discussed and summarized, the instability mechanisms and stability characteristics of stratified rock slope in the complex disaster environment are obtained.Through the summary and statistics of structure characteristics of many actual slopes, main geometric parameters are selected. Based on rigid body limit equilibrium method and strength reduction method, the law of safety factors and failure surface positions of the stratified rock slope are studied in conditions of different strata inclinations, slope angles and structural face intervals. The failure mechanisms and stability characteristics have been revealed under complex structural conditions of horizontal layer, consequent landslide, vertical layer and anti-dip laminate slopes.(2) The types of slope progressive failure and corresponding mechanical mechanisms in the complex disaster environment have been analyzed. Applying limit equilibrium method and finite element method, the numerical method simulating progressive catastrophe is established.① To analyze the types of slope progressive failure and corresponding mechanical mechanism considering dynamic evolutionary process of the slope disaster, limit equilibrium method and finite element method are applied to study the progressive process of the disaster, and discussed how to implement the gradual extension of failure region.② For the uncertainty factors in slope engineering, such as randomness, fuzziness and so on, the method of slope progressive failure considering uncertain factors is discussed, which combined the fuzzy theory with the probability.(3) Based on investigation of typical domestic landslide disasters, the failure mechanism and stability characteristics of slopes affected by the rainfall are further studied, considering the interaction and the nonlinear deformation induced by the unsteady seepage during the rainfall infiltration.The theory of unsaturated soil, saturated-unsaturated seepage, strength and the method of slope stability in the rainfall infiltration are discussed systematically in detail, and safety evaluation method coupling transient seepage and stress fields is also studied, with the consideration of nonlinear deformation induced by unsteady seepage. Combined strength reduction technique to calculate slope stability considering transient seepage, and implemented the evaluation method of failure approach index(FAI) by the coupling of seepage and stress fields based on ABAQUS, revealing slope rock mass strength reserve, the degree of damage and criticality of non-rupture areas quantificationally to explore the impacts of heavy rainfall characteristics on slope failure mechanism and stability from various angles.(4) Coupling the unsteady seepage and the nonlinear deformation of soil, the instability mechanism and slope stability have been conducted under the effects of water level variations(including dips and swells), which combined steady seepage in the early time of water level changes with unsteady transient seepage in the process of water level variation.Based on the principle of flood routing, the process of water level variations of bank slopes have been analyzed, taking the factors of flood processes, flood control storage and discharge capacity into account. With the help of secondary development of ABAQUS, a user subroutine which defined a continuous function of pore pressure with time and space has been created to set the boundary of slopes, presenting dynamic continuous changes of water levels over time. Using the technique of field variables to discount automatically, safety factors at a certain water level has been obtained, thus realized combination between level variation, seepage, and deformation with stabilization organically. On this basis, the interconnection between transient seepage field and stress field under water level dips and swells is conducted. The paper has also discussed the impact on seepage, deformation and slope stability induced by different permeability coefficients, the velocity of water level variations and matric suction conditions, and also revealsed the basic laws of slope catastrophe under the water level changes.