Study On Surface Fissure And Permeability Of Red Clay Under Drying And Wetting Cycle

Guilin belongs to a subtropical monsoon climate with high temperatures and rainy weather throughout the year,and the rain and heat are basically the same in the same season.In this natural environment,red clay fissures due to repeated swell-shrinking,resulting in increase of permeability and reduction of strength,which is likely to cause geological hazards.Therefore,it is very important to understand the fissures characteristics and permeability of red clay in repeated drying and wetting cycle for slope stability and road foundation diseases.The studying on the development of the fissures of remolded red clay can provide reference for the treatment and prevention of such engineering problems.This study takes Guilin Yanshan District red Clay as an example.Through wetting and drying cyclic test,to study the effect of drying and wetting cycle on the surface fissure development and permeability of red clay soil by digital image processing technique and MATLAB software.The main research contents and results are as follows:(1)The digital camera is used to photograph the surface fissure of the red clay to acquire the digital image of the fissure,and the traditional image processing method is improved in the Matlab software environment,thus the statistical accuracy and accuracy of the fissure rate are improved.The fractal dimension of fissure binary image is calculated by Matlab software.The relationship between fractal dimension and fissure rate of soil is analyzed.(2)The effects of different dehydration temperatures on the development of fissure in red clay were studied by dehydration tests.The results show that at lower dehydration temperature,red clay has a peak in the fissure area during wetting and drying cyclic test,while at higher dehydration temperature,the fissure area shows an increasing trend.(3)The effects of different humidification ways on the fissure development of red clay were studied by wetting test.The results show that the spray saturation has obvious effect on the surface scour and disturbance of small size specimen,which is not conducive to the extraction of fissure feature,and the first tension fissure produced by vacuum saturation method can control the development of wetting and drying cyclic fissure.(4)The wetting and drying cyclic of the sample is performed five times.The results show that the fissure morphology and distribution on the surface are affected by the initial moisture content,and the fissure rate decreases with the increase of the dry density.The change rule of the same fissure evaluation index in wetting and drying cyclic can be roughly divided into three categories.(5)Through the variable head permeation test,the change curves of the permeability coefficients with different dry densities and different moisture content in the five wetting and drying cyclic were studied.The results show that the permeability coefficient of red clay decreases significantly with the increase of dry density,increases with the increase of initial moisture content,and peaks at the optimal moisture content.The development of fracture can be reflected by the change of permeability coefficient process.