Study On Failure Law And Mechanism Of Expansive Soil Under Drying-Wetting Cycle

Expansive soil is that has the obvious response to the change of environmental humidity.Expansive soil is widely distributed in China.Frequently engineering accidents due to rainfall and drying cycles have caused significant property losses and serious environmental damage to residents.Scholars at the domestic and international have done a lot of research that plentiful and substantial achievements on the expansive soil slope.But there are few reports on the development prediction and failure behavior of expansive soil crack.To investigate the evolution law of water content and the mechanism of soil crack development in the low permeability boundary.The crack development test is carried out based on a large-size compacted expansive soil sample.Through the sensor,the evolution law of water content in the evaporation process is monitored.The acoustic sounder is used to measure the change of crack development depth.The self-made binary image processing program was used to quantitatively analyze the surface cracks,calculate the crack area ratio of soil,explore the crack failure mechanism and crack development law,and verify it in the indoor slope test.Finally,through PFC simulation software,the failure results of expansive soil crack slope are analyzed by using slope crack parameters.The specific research results are as follows :1.Through the self-made expansive soil drying-wetting cycle device,the expansive soil drying-wetting cycle test was carried out.By monitoring the change of water content in different soil depths,the influence of water content gradient on the change of soil cracks is analyzed.The higher the water content gradient,the more obvious the crack development of soil.The variation law of crack depth,crack area and water content of cracks was explored,and the reasons for the rapid increase of water content in soil after the development of cracks were expounded.The crack development law was verified by the slope failure model test,and the slope crack parameters were measured.2.The contact mode and arrangement of soil particles were observed by electron microscope.Microcosmic analysis of evaporation from the liquid bridge between soil particles to the formation of soil cracks that the essential reason for cracks in the soil.Observing the drying-wetting cycle process of soil by the camera on the side and top of the soil.The cracking behavior of soil under dry conditions and collapse healing and expansion healing behavior of soil under rainfall conditions are analyzed.and the failure mode of cracks on the soil.The selfmade image processing technology is used to quantify the soil cracks,show the development process of soil cracks,and elaborate the development mechanism of expansive soil cracks.3.Based on the measured crack parameters of the slope,the crack parameters are substituted into the slope simulation model by PFC software,and the slope has experienced different times of drying-wetting cycles in a generalized way,resulting in the development of different cracks.The influence of cracks on expansive soil slope under dry-wet cycles is obtained.