Comparative Analysis And Application Of Direct Shear And Triaxial Strength Indexes Of Cohesive Soil In Jingzhou City

The parameters of soil strength have an important influence on the selection and design calculation of foundation pit engineering.The selection and value of shear strength index directly affect the safety and economy of foundation pit engineering.In Jingzhou and even the whole Hubei area,many geotechnical investigation reports only provide quick shear strength index of soil mass,which brings a lot of inconvenience to underground and geotechnical engineering design.In this paper,the comparative analysis of shear strength index between quick shear test and triaxial test(UU)has been carried out on the typical cohesive soil of Jingzhou City.The relationship between direct shear strength index and triaxial strength index has been established with regression method,and the obtained results have been applied to the design of foundation pit engineering.The main contents are following:(1)The shear strength theory and the research progress of shear strength test have been introduced.(2)The shear strength test principle,instrument and procedure have been introduced in detail.(3)The direct shear test and triaxial test have been conducted and compared on the typical cohesive soil of Jingzhou City.The results show that,at the same soil depth,the cohesion value of direct shear test(fast shear)is smaller than that of triaxial test(UU),while the internal friction angle of direct shear test(fast shear)is larger than that of triaxial test(UU).There is a strong correlation between direct shear index and triaxial strength index,which can be fitted with a quadratic equation of one variable.(4)ABAQUS software is used to simulate the deformation characteristics of soil samples under the conditions of direct shear test(fast shear)and triaxial test(UU).The results show that the trend of stress-strain curves obtained from the simulation is similar to that of the tests,which further verify the rationality of the strength index relationship.(5)Based on the research results,the characteristics of foundation pit supporting structure have been compared and analyzed by using different foundation pit design softwares.It can be seen that the calculated results under different test conditions have a little difference,and the calculated value of foundation pit deformation by triaxial strength index is closer to the measured value.