Study On Mechanical Properties Change Of Cohesive Soil And Slope Stability Under Dry-wet Cycles

Compared with sandy soil,clay soil has the physical properties that shrinkage when water is lost,expansion occurs when water is absorbed.This interaction between soil and water will greatly weaken the original structural strength of soil,which is closely related to the engineering properties of soil.Due to the climate,the soil mass in nature is often in the cycle of rainfall infiltration-sun evaporation,and after the dry-wet cycle,the internal structure of the soil mass is damaged,resulting in the development of cracks in the soil mass,which has an irreversible impact on the mechanical properties of the soil mass.Therefore,it is of great theoretical and practical significance to study the mechanical properties of clay and slope stability analysis under the condition of dry-wet cycle,and to provide theoretical basis for preventing the instability of geotechnical structures.In this paper,the damage of dry-wet cycle process to soil stability is taken as the research background,and the dry-wet cycle process in nature is simulated through laboratory experiments.The direct shear test after dry-wet cycle,crack development observation,unconfined compression test and slope numerical simulation are carried out on clay samples,and the failure law of mechanical properties of soil caused by dry-wet cycle process is comprehensively summarized and analyzed.The main research contents and achievements are as follows:(1)Direct shear tests were conducted on clay samples with different dry densities after dry and wet cycles.The results show that the shear strength of soil samples is reduced by the dry-wet cycle process,and the first dry-wet cycle process has the largest effect on the attenuation of shear strength of soil.By analyzing the influence of cohesion and internal friction Angle on the shear strength parameters during the dry-wet cycle,it is found that the decrease of shear strength of soil is mainly caused by the decrease of adhesion between soil particles.(2)The crack development of clay samples after the dry-wet cycle was observed,and the PCAS system was used to quantify the observed results.The results show that the surface crack rate of the soil sample increases with the increase of the number of dry and wet cycles,which is manifested by the increase of the surface crack area and the gradual formation of crack skeleton.The development of cracks in the soil causes the separation of soil particles,which reduces the cohesion between particles,and finally leads to the attenuation of the shear property of the soil.(3)Unconfined compressive tests were carried out on clay samples with different dry densities after dry and wet cycles.The results show that the compressive strength of soil decreases with the increase of dry-wet cycle,and the first dry-wet cycle has the greatest effect on the attenuation of compressive strength of soil.The compressive strength of soil also increases with the increase of dry density,and the peak axial stress of soil with higher dry density is also larger.(4)Using the finite element simulation software ABAQUS,the model of viscous soil slope under different states was established.Taking a viscous soil slope studied by Dawson as the research object,it was found that the stable state of viscous soil slope would be damaged by the dry-wet cycle,that is,the stability safety factor of slope would decrease with the increase of dry-wet cycle.The maximum displacement after instability also increases with the increase of dry and wet cycles.