Triaxial Test Of Silty Clay Unsaturated Soil In Changchun Area

The unsaturated silty clay in the Changchun area is an old Pleistocene alluvial sedimentary soil,which is a geological environment often encountered in engineering construction.For undisturbed soil samples,Using a laser particle size analyzer,a GEO-expert pressure plate instrument,a triaxial unsaturated soil instrument,an in-depth study of the soil-water characteristic curve,the fractal theory,shear strength and other parameters of undisturbed silty clay.Mainly discussed the influence of matrix suction on the strength index of unsaturated silty unsaturated clay,The test results of expriment indicates that the soil-water characteristic curve of silty clay in Changchun region is more precisely fitted by the VG model.Useing of laser particle size analyzer to test the particle size composition of undisturbed soil,Then calculate the fractal dimension,Based on the Bird fractal model to predict the soil-water characteristic curve,It is concluded that the predicted value is in good agreement with the measured value.It is feasible to use the classification theory to predict the soil-water characteristic curve.Using the matrix suction as a variable,the unsaturated silty clay was subjected to triaxial testing of unsaturated soils and the shear strength parameters were obtained.Under certain confining pressure conditions,with the continuous increase in die suction,the cohesive force increases significantly,and the friction angle increases slightly;According to the shear strength parameters obtained from the unsaturated soil test and further combined with the soil-water characteristic curve test,it is concluded that as the volumetric water content increases,the friction angle and cohesive force decrease.The experimentally obtained parameters,Midas GTX is used for foundation well engineering simulation research,Mainly simulate and analyze the influence of excavation depth and matrix suction on the surrounding ground settlement and horizontal displacement of the ground wall.The simulation results indicates that the excavation depth is one of the important factors affecting the settlement of the surrounding surface and the horizontal displacement of the soil wall;When the excavation depth is fixed,the suction of the die continuously increases,and the surface settlement and horizontal displacement of the soil wall gradually decrease and finally stabilize.For foundation pit engineering,the shear strength index is an important technical parameter that affects the foundation pit support system.Matrix suction is the key to the analysis of unsaturated soils,and it is also the basic work for numerical simulation analysis of foundation pit support.For unsaturated soils,accumulating a large amount of test data is of great significance to theoretical research and engineering applications.The experimental research work carried out in this paper provides more reliable technical parameters for engineering practice in Changchun area.