Study On The Seepage Law Of Precipitation In Soil Slope And Its Influence On Slope Stability

The artificial accumulation slope represented by open-pit mine dump is prone to slope instability due to rainfall.The water content in the slope and the flow law of water have an important influence on the slope stability.Therefore,it is of great significance to study the seepage law in the slope and the change law of cracks formed by seepage to ensure the safety of the slope.In order to study the seepage law of rainwater in the slope and the resulting crack changes during rainfall,a physical model of the slope of the dump in Bayan Obo West Mine was established.By simulating artificial rainfall,the movement of water in the slope during seepage was detected by using high-density resistivity method.A total of three concentrated rainfalls were carried out in the experiment,and the initial rainfall intensity was 0.62 mm / min.The first and second concentrated rainfalls adopted the method of ’ rainfall-measurement-re-rainfall-remeasurement ’ cycle,and gradually measured the change of apparent resistivity in the infiltration slope with water flow.The time interval between the adjacent two rainfalls was 15 min.In the third concentrated rainfall,the ’ low rainfall intensity and long duration ’ rainfall was first used,and then the rainfall intensity was increased to 2.17 mm / min and continued to measure.The changes of apparent resistivity and surface cracks in the slope with the infiltration of water were observed.The research shows that with the progress of rainfall,the inversion apparent resistivity inside the slope changes from horizontal uniformity to high apparent resistivity anomaly,and then experiences the cycle of ’ increasing-decreasing-increasing-decreasing ’.However,the cracks on the slope surface appear from the first concentrated rainfall to the second concentrated rainfall,and then experience the cycle of ’ splitting-closure-splitting-closure ’.After the rainfall is over,the cracks are split again when the ventilation is dry,and finally the cracks are gradually widened.Due to the small initial rainfall,the slope soon reached a new balance.In the third concentrated rainfall,the slope still did not change significantly after 253 min of continuous accumulated rainfall using the method of ’ low rainfall intensity and long duration ’.Then,the rainfall intensity was increased.After 5 min,new cracks could be seen on the slope.At the same time,the original cracks continued to widen.Due to the saturation of soil moisture caused by continuous rainfall,the slope stability decreased under the combined action of seepage and runoff.Then,the time-lapse geophysical method was used to analyze the apparent resistivity change rate,residual value and apparent reflection coefficient of the slope model data.The analysis shows that the time-lapse geophysical method can be used to monitor the slope during rainfall seepage,and the main change area of the slope is the shallow area.At the same time,the time-lapse geophysical method can better find the hidden dangers in the slope.In this thesis,the high-density resistivity method is used to detect the change of slope model cracks under the condition of rainfall seepage step by step.From the inversion image and observation data,it is known that the slope cracks are from scratch when rainfall seepage occurs,and the cracks gradually widen with the seepage.The stability of the slope model before and after the experiment was analyzed by Sweden slice method and simplified Bishop method,and the change of slope stability during the experiment was analyzed theoretically.The analysis shows that the influence of seepage on slope stability is relatively slow.When the slope is wetted,heavy rainfall occurs,the slope stability coefficient decreases obviously,and the slope tends to change in the direction of instability.