| As a typical high plastic clay,expansive soil is often in unsaturated state in natural state,which has a control effect on the overall stability of bank slope.Danjiangkou reservoir is the starting place of the middle line of South to North Water Diversion,and the soil mass of reservoir slope is mainly expansive soil.Therefore,it is important to study the stability evolution of expansive soil slope for ensuring the safety of water source.This paper takes the expansive soil bank slope of Danjiangkou Reservoir as the research object,and uses the method of combining physical model and numerical simulation to analyze the response of the deformation and stability of the expansive soil bank slope under the fluctuation of reservoir water level and rainfall conditions.The main research is to study the influence mechanism of water factors on the expansive soil bank slope.The research results can provide theoretical basis for solving the engineering problems caused by the expansive soil bank slope.The main research contents are as follows:(1)Through field drilling sampling,indoor mechanical test and expansibility test,the physical and mechanical properties of expansive soil on bank slope are obtained,and the region is determined to be medium weak expansibility,which provides basic data for material ratio of physical model test.It is found that the cohesion and internal friction angle of remolded expansive soil have a linear relationship with dry density and a quadratic relationship with water content,and the interaction between them is obvious.(2)Based on the similarity theory,the similarity criterion of main influencing parameters of expansive soil on bank slope is derived,and the similar soil sample is prepared,and the physical model is constructed in the built model tank with equal scale reduction in practical engineering.Based on the comprehensive analysis of the monitoring data of internal displacement and seepage pressure,the change law of internal displacement and pore water pressure is consistent with the rise and fall of water level: the internal horizontal displacement first decreases slightly and then increases reversely with the rise of water level,and when the water level drops,the horizontal displacement rises slightly;the pore water pressure decreases with the rise of water level and decreases to the minimum when the water level rises to the maximum It increases slightly with the fall of water level.When the water level changes greatly,the corresponding change range of internal horizontal displacement and pore water pressure also increases.(3)The finite element model of the test bank slope is established.Based on the fluid solid coupling principle of unsaturated soil,the variation laws of the seepage field,stress field and displacement field of the bank slope under the conditions of reservoir water fluctuation and rainfall are analyzed.Through the comparison with the monitoring data,the correctness of the numerical simulation is verified,and the internal displacement and pore water pressure are in good agreement.The displacement of bank slope increases with the rise of water level,decreases with the fall of water level,and the pore water pressure decreases with the rise of water level,but rises with the fall of water level.(4)According to the stability analysis and calculation of expansive soil bank slope,during the period of water level rising,the slope stability coefficient begins to rise rapidly and reaches the maximum at the highest water level.When the water level is stable,the slope stability coefficient first decreases and then remains stable;during the period of water level falling,the slope stability coefficient decreases rapidly;during the period of water level falling to stability,the slope stability coefficient rises slightly.On the whole,the bank slope is still in a safe state,but in practice,when the continuous rainstorm and water level changes,and considering the fissure of expansive soil,the stability coefficient will decrease greatly,which will lead to the instability of the bank slope. |
