Experimental Study On Water Loss Cracking Characteristics Of Guilin Red Clay

The red clay water evaporates and produces shrinkage cracks,resulting in enhanced permeability and reduced strength of the soil,which is easy to cause geological disasters such as slope instability and uneven settlement of the foundation.In-depth study of soil moisture evaporation and cracking characteristics is helpful to prevent and deal with related engineering problems.In this study,the red clay in guilin city was taken as the research object and compacted soil and saturated mud were used as sample types in the test.The effects of initial moisture content,soil thickness,ambient temperature,soil composition(kaolin,quartz),and modified materials(fly ash,lignin fiber)on moisture evaporation characteristics and fracture development of red clay were studied through indoor soil desiccation cracking test,Based on PIV particle velocity measurement technique,the fracture development process and shrinkage characteristics of red clay were analyzed from the perspective of soil surface deformation.The main conclusions are as follows:(1)Through soil moisture evaporation test,the influence of the above factors on the moisture evaporation characteristics of red clay was quantitatively analyzed.The results show that the maximum evaporation rate is positively correlated with the initial moisture content,thickness,temperature and quartz sand content,while the maximum evaporation rate is negatively correlated with the content of kaolin,fly ash and lignin fiber.The total evaporation time was positively correlated with the initial moisture content,thickness and content of kaolin,fly ash and lignin fiber,while the total evaporation time was negatively correlated with temperature and quartz sand content.(2)Digital image processing technology was used to process the surface digital image of red clay in the process of water loss and cracking test to obtain crack parameters,and a crack measurement system suitable for the study of surface crack of red clay was established.The influence of the above factors on the crack development of red clay was analyzed.The results showed that the degree of fracture development of the red clay sample was negatively correlated with the thickness and kaolin content,and positively correlated with the initial moisture content,temperature and quartz sand content.The addition of 2%?6% fly ash or 1%?4% lignin fiber can inhibit the development of cracks in the red clay,which can be expressed in the following ways: reducing the crack parameters of the compacted soil,reducing the amount of soil divided by cracks in the saturated mud sample,and increasing the soil area.(3)Changes of surface displacement field and strain field in the process of water loss and cracking of red clay were analyzed by PIV particle velocity measurement technology.The results show that the displacement field and strain field change with the development of crack and the shrinkage of soil mass.For a single soil mass,the displacement and strain strength of soil mass in the direction perpendicular to the boundary of soil mass in the direction of crack are the largest.In the process of losing water,the red clay shrinks towards a point in the center of the soil mass,and the soil mass shrinks outwards along the center.