Study On Slope Stability Considering Strength Weakening Of Red Clay

Red clay is widely distributed in Guangxi.As a special kind of soil,red clay has the characteristics of high natural moisture content,high plasticity and large void ratio,as well as high resistance to damage and compression deformation.Therefore,with the continuous expansion of traffic infrastructure scale,remolded red clay will be used in Subgrade Slope filling,and it will be used in road construction The undisturbed red clay slope is often encountered in cutting excavation.Under natural conditions,the strength of red clay is easily weakened by the influence of external environment and accumulated strain.At present,the research on the shear strength weakening of two types of red clay is relatively less at home and abroad,and the research on slope stability does not consider the residual strength of red clay.Therefore,the research on the strength weakening of red clay is of great significance in theory and engineering practice for the correct evaluation of the safety and stability of slope.In this paper,taking Guangxi red clay as the research object,through the indoor geotechnical test of undisturbed soil and remolded soil as well as the finite element numerical simulation calculation and other methods,the weakening of shear strength of red clay caused by accumulated strain and water and the analysis and research of red clay slope stability are carried out.The main work and conclusions are as follows:(1)Repeated direct shear tests were carried out on the undisturbed red clay with different water content.The results show that under the same vertical pressure load,when the undisturbed red clay goes through the same shear displacement,the corresponding shear stress is related to the moisture content of the soil sample.The strength change of undisturbed red clay is the result of the interaction of internal friction angle and cohesion.The weakening of strength will lead to the decrease of both strength indexes,but the deterioration degree of the two indexes is different.(2)Repeated direct shear tests were carried out on remolded red clay with different water content.The results show that under different vertical pressures,the general trend of shear stress displacement curve of remolded red clay is approximately the same.With the increase of moisture content of soil sample,the increase rate of shear stress at the initial loading stage gradually slows down and the overall shear strength gradually decreases under the same vertical pressure,which indicates that the increase of moisture content will lead to the decrease of shear strength of soil sample Low.Under the peak strength,the internal friction angle and cohesion of remolded red clay decrease with the increase ofwater content,but the rate of decrease varies with the range of water content.(3)Through the improvement of the simplified Bishop method,the calculation method of the slope safety factor considering the residual strength is obtained.The residual coefficient R and the parameter n are the key parameters to determine the slope safety factor.When 40%-60% of the soil on the sliding surface of the slope enters into the residual strength,the safety factor decreases fastest,and the stability of the slope is more dangerous.With the increase of n/N,the safety factor of slope is decreasing.(4)The numerical simulation of progressive failure of red clay slope based on strength weakening is carried out.The results show that the increase of water content will lead to the decrease of safety factor of red clay slope stability.Under the same water content condition,the safety factor of slope decreases with the increase of residual coefficient R.With the increase of slope I,the safety factor of slope decreases first and then increases.