Rainfall Infiltration And Stability Of Shallow Slope Considering Initial Groundwater

Zhejiang Province is one of the provinces prone to frequent occurrence of landslide geological disasters in China,and shallow landslides caused by extreme rainfall such as typhoon torrential rain or continuous plum rain every year pose a serious threat to the lives and properties of local people,becoming an important public security issue affecting the economic and social development of the province.However,in recent years,most landslide disasters have not occurred in the key risk prevention areas,which shows that current research has insufficient understanding of the occurrence mechanism of rainfall induced landslides in groundwater-enriched areas.Taking the landslide in Wuxie scenic area of Zhuji city on June 10 th,2021 as an example,this paper carried out on-site investigation and indoor geotechnical experiments,and then analyzed the causes of the landslide;based on the soil moisture content exponential distribution model determined by considering the unsaturated characteristics of soil,the analytical solution model of rainfall infiltration process for shallow slope was derived,and its stability under different rainfall conditions was evaluated;considering the similarity law of rainfall simulation and the Coriolis effect of raindrop movement,a set of airborne rainfall simulators for supergravity environments was developed;finally carried out two supergravity tests of rainfallinduced shallow soil landslides with or without introduction of initial groundwater conditions;by comparing the test results and theoretical analysis results,a method for analyzing the stability of shallow slopes with the influence of initial groundwater is proposed.The main conclusions of this paper are as follows:(1)The Zhuji landslide occurred in the overlying soil layer of bedrock,and the ratio of the failure depth to the slope length is small,the overall performance is a shallow soil landslide;heavy rainfall and initial groundwater are the main triggers for this landslide.(2)Combining the improved rainfall infiltration model with the shallow slope stability analysis model,the results show that for shallow slopes with initial groundwater,the failure will occur at the bedrock surface under rainfall conditions,and the instability time is earlier than the prediction results of the traditional model.(3)The results of supergravity test show that for the bedrock shallow slope with uniform distribution of initial moisture content,the overall sliding of the slope occurs under rainfall,and the maximum prototype failure depth is 1.98m;for the shallow slope with initial groundwater,the maximum prototype failure depth in the slope is 3.51 m,and the instability process starts from the middle and rear of the slope and sliding along the soil near the bedrock face,and when the initial groundwater is introduced,the maximum failure depth of the landslide increases by 77.3%,and the failure time is advanced by 48.3%.(4)The relative error between theoretically calculated failure time and test results is only 8.82%,so the improved stability analysis model can be used to predict rainfall-induced shallow soil landslides.(5)Using the improved stability analysis model to calculate the failure triggering time of the slope when the rainfall intensity is 35mm/h,the relative error between the calculation result and the actual failure time of Zhuji landslide is only 5.33%.