Study On Rainfall Mechanical Response And Safety Evaluation Of Soil Slope Along High-Speed Railway

With the recent rapid development of Chinese economic construction, especially in the implementation of the western development strategy in resource development and infrastructure construction, there has been a lot of high and steep slope. It is imminent to carry out research work related to mitigating disaster because of the increasing disaster of slope engineering with the height and angle of the slope engineering increasing by the restriction of the engineering geological and topographical conditions and recent natural disasters exacerbated by heavy rains and floods etc. Therefore the disasters mechanism of soil slope caused by rain in our country is researched and analyzed in this paper from unsaturated soil mechanics, slope engineering, fluid mechanics, and experimental mechanics(1) Based on the typical soil and slope conditions in the southwest mountainous area, the unsaturated silty clay’s mineral composition analysis test, soil particle composition analysis test, compaction test, unsaturated soil water test, direct shear test, consolidation tests have been carried out, and the soil water absorption and exsorption curve of different void ratio and graded composition was obtain, and based on the above factors. The Feng-Fredlund model was modified to explore the influence of the void ratio and soil matric suction for shear strength, and the reason of soil softening at different matric suction was explained. The computing method of elasticity modulus of unsaturated soil is proposed with the unsaturated soil consolidation test.(2) Based on the study of former investigator, the Green-Ampt model was introduced to the overland flow problem, and the original one-dimensional model could be extended to three-dimensional space by coordinate transformation. Meanwhile the basic equations of slope runoff-infiltration was deduced and proceed by numerical discretization finite through the difference methods. Commercial finite element program Abaqus and the Fortran language were used to numeralized the above algorithm, and the rationality was proved by an example.(3) While the rain infiltrated into the slope, the closed bubble continued to be compressed before the phreatic line, which made the air pressure increasing and a block effect strengthening. The enclosed gas made the permeability coefficient of the water in the soil decreasing. Therefore, the effect of gas on the slope infiltration should be considered and the solid-liquid-gas coupling computing method should be adopt in the calculation. Comparative verification study suggested method ignoring the fluid-solid coupling method in the slope calculation appeared too fast saturation line expanded rate, which is different from the actual situation. The method in this paper is consistent with the simple solid-liquid-gas coupling method (Hu ran, etc.) in the long rain conditions. The phreatic line achieved by this paper located between the method ignoring the fluid-solid coupling method and the solid-liquid-gas coupling computing method in short rainfall conditions. But the difference decreased slightly with the time continuing. It suggested rainwater infiltration gas closed, compression of deep slope, and overland runoff-Infiltration should be considered in order to get a more scientific and reasonable findings.(4) Analyze the advantages and disadvantages of the existing rainfall technology in the centrifugal field and integrated monitoring systems, and a new type of centrifuge rainfall systems and fiber grating monitoring systems and components were developed combined with rainfall atomization technology and fiber grating testing techniques. One new type of rainfall spray system using eddy current technology make a better uniformity of rain, while erosion phenomenon caused by excessive raindrop splash in the previous slope trials were eliminated. The new centrifugal fiber grating FBG monitor system composed by displacement meter, anchor dynamometer, pile strain gauge, et, which could effectively ensure the validity of the test in the centrifuge conditions and the verification testing demonstrate that the method can get a better test results than the electrical test component.(5) Based on the similarity principle, the similarity parameters of centrifugal rainfall of slope were derived, and the comparison, selection and testing of the relevant materials were carried out. a comprehensive set of test processes of selecting material, selecting monitoring original, original layout, and loading, monitoring of the test of the slope rainfall centrifuge test were formed.(6) Combined with the new centrifugal rainfall devices and the fiber grating integrated test system, a group of 10 soil slope centrifugal rainfall model tests were carried out under conditions of different rainfall conditions, retaining conditions, slope conditions, stratum conditions, etc. The evolution characteristics of the factors of the displacement change during the test slope, moisture content change, pore pressure change, retaining force structure change, and the typical slope failure mode were obtained with time changing.(7) Based on the previous studies and Fortran-based language and finite element program Abaqus, combined with the slope runoff-infiltration, unsaturated solid-liquid-gas coupling theory, a FEM secondary development is made, and a reasonable calculation module is drawn. Then, combined with the earlier model test the numerical simulation was proceed, and it obtained the distribution patterns and variations of the effective stress field, matric suction field, displacement field, supporting structure force, etc. The verification of the model test at the typical time during rainfall suggested the correction of the test.(8) Based on Rough Set and support vector machine approach, combined with 30 soil engineering slope survey along the Gui-Guang, Lan-Yu, Cheng-Mian-Le high-speed railway, southwest mountain slopes safety evaluation method is proposed from a macro perspective. Based on Catastrophe Theory, slopes safety evaluation criteria under rainfall conditions of driven failure mode and push failure mode were established, which can identify the rainfall influence ranges of slope instability.