Research on Sensitivity of Influence Factors on Soil Landslide Stability
|School||Chengdu University of Technology|
|Keywords||soil landslides sensibility influencing factors estimation of stability numerical analysis orthogonal experimental design|
Lots of the soil landslides were triggered by the "5.12" Wenchuan Earthquake, especially, Qingchuan earthquake disaster region far away from the epicenter, but its disaster-affected degree was very serious. In view of the reality that lots of soil landslides were triggered between the Earthquake, it is of very important significance to develop the sensitivity research of the seismic soil landslides disasters in theory and in practice, under the present economic and technical conditions that they could not been exploration and protection thoroughly. Based on the previous researchers, to based on the fieldwork and data which we collect in Qingchuan earthquake disaster region, taking soil landslides in Qingchuan County, which is Strong earthquake high-intensity region(Ⅶ),as research object. The paper studied the sensitivity of the seismic soil landslides disasters by orthogonal test method in a systematic way, based on the following aspects: To characteristic of soil landslides statistics and conduct analysis of that, Based on the characteristic Influence factors which influenced the stability of seismic soil landslides were studied in a systematic way, and, meanwhile, the correlation and ranking functions were studied between influence factors on the seismic soil landslides disasters in Qingchuan earthquake disaster region, And, using the famous finite element analysis software——The GeoStudio2004, we conduct numerical analysis for the stability of soil landslides. Which are analyzed by engineering geological analysis method, engineering geological statistical methods, engineering geological numerical analysis method. Some achievements obtained are in the following aspects:(1) The study area belong to high intensity area ,where seismic intensity isⅦdegrees, basic earthquake acceleration is 0.15 g, and its geological structure is complex, mainly distributing Dujiangyan-Jiangyou fracture, Yingxiu-Beichuan fracture, Pingwu-Qingchuan fracture, among them, Yingxiu-Beichuan fracture, Pingwu-Qingchuan fracture have strong earthquake activity in the "5.12" earthquake.(2) In this paper, To the characteristics of the soil landslides statistics and conduct analysis of them in the study area, the influence factors of the seismic soil landslides disasters were analyzed. It was finally known from results of statistical analysis that, the areal geologic structure is main influence factors and plays a key role in distribution of the seismic soil landslides disasters. Lots of the soil landslides were distributed near active strong fault; The specific topography and landforms tends to appear in amplification effect of the seismic wave in slope, Displacement amplification coefficient, speed and acceleration amplification coefficient, the seismic soil landslides disasters were mainly distributed that elevation is 700 m to 900 m (77%), relatively elevation is about 10 m to 100 m (76%), the middle- upper part of the slope, its average slope is 20°-39°(71%), the concave slope type of the slope holds quite large proportion (43%),and the soft rock strata, and it can also be related to the tendency and inclination of the rock formation, In this area, The main strata lithology of landslides is phyllite and slate(50%), the bedding landslide account for the greater proportion(61%), the inclination of the rock formation is about 30°-39°(53%); Taking into account the interface effect of the structure of rock and soil about propagation of the Seismic waves in the rock-mass and soil-body, Intricate dynamic stress differentiation were shown near various interface, In particular, Stress isoclines image is more intensive and sharp transition; The type of the rock-mass and soil-body has two action, On one hand, it damping propagation of the Seismic waves in the rock-mass and soil-body, on the other hand, it is the embodiment of the physical and mechanical characteristics in stability of slope that is talus landslide in research area It is indispensable for the water about stability of slope, after Wenchuan big earthquake happened, the rainfall was the primary factor for soil landslides, and, the pore water pressure of constant growth, make failure of the seismic soil landslides disasters rapid development during the "5.12" Wenchuan Earthquake. In short words, the influence factors of the seismic soil landslides disasters were analyzed, such as The specific topography and landforms, The lithology, The tendency and inclination of the rock formation, The structure of the rock-mass and soil-body, The type of the rock-mass and soil-body , The regional geological fault, The hydrogeology conditions.(3) The paper points out that the finite element stress-based approach that of combining the limit equilibrium method with the finite element method, types of analyses for assessing the stability of the soil landslides is reasonable and accurate. The chapter discusses the fundamentals of limit equilibrium formulations, points out the limitations, explores what can be done to overcome the limitations, and ends with general guidelines on the continued use of the method in strong earthquake high-intensity region in practice. And then, the finite element method of analyses for assessing the stability of the soil landslides were carried on the comprehensive analysis, Including the material constitutive model, seepage theory, stress analysis theory in static condition, the slope dynamic response analysis theory, coupling theory between the stress field and the seepage field of slope body. Finally, using the combination of the two methods, it is concluded for the soil landslides stability coefficient formulation about the finite element stress-based approach. Comparison results on the stability of the soil landslides, which were calculated by using the famous 2-d finite element analysis software (GeoStudio2004) and the limit equilibrium method in every situation, points out that the stability coefficient have a little difference within 10% ,except the stability of the seismic soil landslides disasters, between the finite element stress-based approach and the limit equilibrium method, that the finite element stress-based approach types of analyses for assessing the stability of the soil landslides is reasonable in strong earthquake high-intensity region.(4) To influencing factors, which affect the stability of seismic soil landslides, statistics and conduct quantitative analysis of them by Engineering geological statistical methods in the study area, it is known that some of these factors have certain relevance and obey certain function relations. Based on the conclusion of statistics analysis, these factors, whose have certain relevance, can be divided into three categories such as Natural cohesion, Saturated cohesion, and aspect of slope, and Natural density, Saturated density, angle of slope and elevation, and Natural internal friction angle, Saturated internal friction angle. And, Natural cohesion and Saturated cohesion, Natural internal friction angle and Saturated internal friction angle, Saturated density and elevation, Natural density and elevation meet hyperbolic, Natural cohesion and the slope tendency, Saturated cohesion and the slope tendency meet S curve, Natural density and slope, Saturated density and slope meet logarithmic curves, Natural density and Saturated density meet index curve 2, and, the relative elevation and elevation meet linear function.(5) Based on the research in the above three aspects, with the orthogonal experiment design theory, the stability influencing factors of seismic soil landslides of the study area are analysis on the sensitivity of them ,which are divided into the Soil character and external factors. The paper probes into sensitivity analysis of the two stability affecting factors from various angles, considering the shallow landslides, the medium-depth landslides, and the deep-seated landslides three kinds of circumstances, respectively. Research on the sensitivity analysis of these three kinds of circumstances, the sensibility of Soil character and External factors of the stability influencing factors of the seismic soil landslides are obtained.