Research On The Mechanical Properties Of Red Clay And Slope Stability Under Dry-Wet Cycle

As a kind of special clay,red clay has the characteristics of high liquid limit,high porosity ratio,high strength,low compressibility,etc.,and it is easy to produce dry shrinkage crack due to water absorption,expansion and water loss,which makes it have bad engineering characteristics.Red clay is widely distributed in rainy areas in south China,and engineering problems caused by cyclic rainfall and alternation of dry and wet are often needed to be solved during construction.At the same time,the construction of infrastructure in China's red clay areas is accelerating,and red clay slope collapse,landslide,subgrade cracking and uneven settlement occur from time to time.Therefore,it is of great significance to study the mechanical properties and strength evolution of red clay under the action of dry and wet circulation.In this paper,the red clay of a highway slope in guangxi was taken as the research object to carry out indoor basic physical mechanics test,direct shear test with different moisture content,direct shear test under dry-wet cycle and triaxial test,to analyze the change characteristics of the strength of red clay with dry-wet cycle and the evolution law of constitutive parameters.At the same time,the scanning electron microscope test was carried out on the red clay in the dry-wet cycle to qualitatively analyze the microstructure of the red clay.Three kinds of microstructure parameters were selected to statistically analyze the law of the microstructure parameters under the dry-wet cycle.Finally,a 3d model of the red clay slope is established for plastic deformation and stability analysis.The following conclusions are obtained:(1)the shear strength of red clay will attenuate in different degrees under the action of dry and wet cycling,of which the attenuation is the largest after the first dry and wet cycling,then gradually weakens,and finally tends to be stable.The development of cracks in red clay is affected by both water content and dry-wet cycle.In the dehumidification process,when the water content is within a certain range(20%-15%),the cracks develop most.The development of red clay cracks is mainly caused by the first four dry and wet cycles.(2)the stress-strain curve of the indoor dry and wet cycle test of red clay shows a plastic hardening type,and the strength of the triaxial consolidation and drainage state also decreases with the increase of the dry and wet cycle.The constitutive parameters and cycle times of red clay show a regularity,and the plastic hardening model is suitable for the analysis and calculation of saturated red clay.(3)under the action of dry-wet circulation,the microstructure parameters of red clay have different changing rules.Under the action of dry-wet circulation,the microscopic particles and pores are arranged in a directional manner,the particle size distribution is close to the middle,and the content of ellipsoidal particles is the highest.(4)the red clay slope has a laige cumulative displacement under the action of the dry-wet cycle,and its stability attenuates the most after the initial dry-wet cycle.At the same time,the wet and dry circulation easily causes cracks on the surface of the red clay slope,which adversely affects the safety of the slope.