Study On Structure And Seepage Characteristics Of Structural Clay In Zhanjiang Formation Under Rainfall

The Zhanjiang area of Guangdong Province is located between 109°40’-110°58’ east longitude and 20°13’-21°57’ north latitude,it is close to the South China Sea,it is affected by the tropical monsoon,and has abundant rainfall throughout the year.It has formed under this natural condition a gray clay with strong structural properties,which is called Zhanjiang Formation of structural clay.At the same time,the area is often hit by typhoons and brought heavy rainfall,it often induces geological disasters such as landslides and debris.Heavy rainfall will cause the loss of the internal cementation capacity of the soil,and the connection and arrangement of particles will change,which will lead to the structural damage of the soil.During the rainfall process,the advance rate of the wetting front in the soil is closely related to the soil structure.Therefore,the research on the structure and seepage characteristics of the structural clay of the Zhanjiang Formation under rainfall conditions is of great significance to the engineering practice in the Zhanjiang area.Based on previous studies,taking Zhanjiang Formation of structural clay as the research object,this paper has passed a series of laboratory tests and numerical simulation analysis.The main research contents and results are as follows:(1)Obtain the physical and mechanical property indexes of the structural clay of Zhanjiang Formation at different buried depths through geotechnical tests.(2)Without considering the influence of seepage,the structural damage parameter,a structural quantitative parameter index is introduced.According to the compression curve of the structural clay,the structural damage parameter of the structural clay of the Zhanjiang Formation at different buried depths is obtained,and it is found that the.As the buried depth increases,the structural damage parameter decreases.(3)The soil-water characteristic curves of the undisturbed Zhanjiang Formation of structural clay at different buried depths were measured by the tensiometer method,and the Fredlund-Xing model parameters were obtained by analysis.Through the nonlinear fitting analysis between the model parameters and the structural damage parameter,the establishment.The quantitative relationship between structural properties and soil-water properties of the structural clay of Zhanjiang Formation is established,and its rationality is verified by experimental data.(4)Through soil column infiltration tests,we observed the wetting front migration,wetting front movement distance and infiltration rate of structural clay in Zhanjiang Formation at different buried depths during the test.The monitoring points were obtained by setting up two monitoring points.For the change of volumetric water content,the relationship between the distance of wetting front migration,infiltration rate and time has been established.(5)Through the rainfall data in Zhanjiang area combined with the actual engineering background,with the help of the finite element software Geo Studio,set four rain patterns of rainfall conditions,establish a slope model in an ideal state,and conduct a fluid-solid coupling analysis with or without the existence of a weak interlayer.Considering the influence of weak interlayer and four rain patterns on slope stability,obtain four kinds of rain patterns and the slope pore water pressure,maximum shear stress,maximum shear strain,xy displacement distribution cloud diagram and slope stability safety factor with or without weak interlayer.