Study On Impacts Of Clay Content On Bank Slope Seepage And Stability Characteristics Of Silty Clay

Silty clay slope is widely distributed in water conservancy project in China.Clay contents of soil in different regions are obviously different due to the sedimentary history differences.At present about the influence of clay content on seepage and stability of silty clay slope is not clear,which has a direct impact on the correct safety evaluation of silty clay slope.Taking several bank silty soil slopes of a hydro-jucntion in Xiangjiang River as examples in a thesis,many laboratory tests and numerical analysis are carried out,the influence of clay content on physical and mechanical parameters of silty clay is revealed,and the effects on seepage and stability characteristics of the bank slope are studied,the research achievements provide a reference for safety analysis evaluation and the protection of silty clay slopes.The main research contents and conclusions are as follows:(1)Experimental study on impacts of clay content on soil water characteristic curve of silty clay.The clay contents of six silty clay samples with different regions are determined with the densimeter method and their shear strength were performed by direct shear apparatus.Then,the impacts of clay content on cohesion and internal friction angle of silty clay are analyzed.As the clay content increases from 30.7% to 45.58%,cohesion have keep decreasing from 35.7kPa to 35.7 kPa,Angle of internal friction increases from 17.4° to 20.2°firstly,and then decreases to 15.9°.(2)Experimental study on impacts of clay content on shear strength parameter of silty clay.The volumetric moisture contents of different matrix suctions are measured with the centrifuge.And soil-water characteristic curves of six samples are fitted on VG model.The results show as follows: as the clay content from 30.7% to 45.58%,the coefficient of permeability from 8.26×10-6m/s to 4.71×10-7 m/s,the α increased by 5.4% and the value of n decrease by 3% of VG model.(3)Analysis of effect of clay content on seepage and stability of bank slope.Based on laboratory results by shear strength test and soil water characteristic curve test,seepage field and stability of bank slope with different clay content are simulated under rainfall conditions with SEEP/W and SLOPE module of GeoStudio software.The impacts of caly content on the pore water pressure,seepage gradient,transient saturated areas and safety factor are compared.The results show as follows: As the clay content increases,the lower its pore water pressure,the seepage gradient change is insignificant,the smaller its scope of transient saturated areas,the safety factor of bank slope stability gradually decreases.