| Rainfall as a major cause of the high loess slope instability has become consensus, but the awareness and understanding of this relationship is not sufficient. The infiltration of soil water's transportation is directly related to the distribution of pore water pressure and the variation of suction in process of rainfall. And then which regard to the changes of shear strength of the soil, in addition, the depth of infiltration by rainfall also related to determine the location of the sliding surface as slope instability. Therefore, study on the stability of high loess slope under rainfall makes great practical significance and theoretical value.Based on the synthesized and summarized of predecessors' achievements, select typical high loess slope along the Shanxi South-central Overloading Railway Channel as the research object, combining on laboratory tests and field trials, as well as qualitative and quantitative analysis,numerical and traditional compared limit equilibrium analysis, mechanism analysis and system thorough research on the stability of high loess slope under rainfall have been carried out, and some valuable achievement has been made.Firstly, by means of matrix suction measurement of the samples with different moisture content through unsaturated soils GDS triaxial apparatus, making a certain analysis on the test results to work out Malan and Lishi loess soil water characteristic curve. Then, the shear strength parameters of unsaturated loess have been calculated based on saturated-unsaturated triaxial tests.Secondly, we design a field simulated rainfall system, select the typical high loess slope for different intensity of rainfall experiments which including moderate rain, heavy rain and torrential rain, the time between 60 min and 90 min; measure soil pressure, pore pressure, suction, water content and many other parameters during rainfall in the slope, the rule of rainfall infiltration has been a good understanding at last. At the same time, we draw some other useful conclusions, such as:the permeability coefficient of saturated loess is about 7.282×10-6m/s, heavy rainfall may also induces shallow landslides when the accumulated rainfall reach to 182mm or infiltration next to 4m even in the loess region where is absence of cracks, holes or sliding surface.Further more, based on the aforementioned study of unsaturated loess theory, doing the simulation about loess high slope at K62+80 along Shanxi South-central Overloading Railway Channel in different rainfall condition by GeoStudio numerical software. Then get the transient seepage field which contains pore water pressure and volume moisture content.Finally, the transient seepage field of loess high slope in different rainfall condition at chapter is brought into SIGMA/W analysis module of GeoStudio, as a result, the displacement and maximum shear strain of slope in different rainfall condition can be analyzed with the help of the finite element method. Further more, we choose the improved limit equilibrium method of unsaturated soil slope to analysis the slope stability under the action of unsaturated seepage. Research results can not only provide design basis for engineering, but also made considerable progress in the basic theory and research method. |
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