Experimental Study On Residual Strength And The Index Of Shear Strength Characteristics Of Different Clay Soil

Currently, the protection work of the landslide disaster has attracted wide attention from the engineering and academic circles, but the study on the inherent mechanical mechanism and the protection engineering of the landslide is still not enough. In the analysis of slope stability, the residual strength is usually used as the failure condition, and the ring shear test is one of the most effective methods to study the deformation and strength characteristics of the landslide mass. The DTA-138 ring shear apparatus for 20 different plasticity index of saturated cohesive soil, under the test conditions of the drainage consolidation, systematic experimental study, study under the condition of large deformation of cohesive soil shear strength characteristics; current research method to stress, over-consolidated ratio, plastic index and multistage shearing effect on the residual strength. The variation law of shear strength parameters with the plastic index is studied, and the relationship between the settlement displacement and the current normal stress and the super consolidation ratio is studied. The stability tests of two kinds of saturated cohesive soils, which are Ip=26 and Ip=32, are used to prove the stability of the device. The main contents and conclusions of this paper are:(1)The group of 18 different plasticity index of saturated cohesive soil in the over consolidation ratio is OCR=2, current method to stress were worked as ?0=50k Pa, 100 KPA and 150 k Pa of ring shear test, obtained both silty clay or clay and residual strength with the method to the stress increase significantly increased.(2)Through saturated clay on Ip=15 saturated powder soft clay and Ip=24, Ip =28, Ip =46. In the current method to stress Sigma ?0=50k Pa. Different over consolidation ratio of clay soil, draw over consolidation ratio on the peak intensity has certain influence, but on the residual strength almost no influence.(3)By selecting the saturated clay and Ip =32 Ip =26 under the same over-consolidation ratio, single level shear and multilevel shear experiments, it is concluded that the multistage shear peak strength was significantly lower than that of the single level shear peak strength, multilevel shear residual strength and single level shear residual strength is basically the same. Shear mode has no significant effect on the residual strength.(4)In the large deformation stage, the cohesive soil is close to the critical state, and its strength depends on the soil properties, which is not directly related to the history of stress and the mode of shearing. Under the same current normal stress, the residual strength decreases with the increase of the plastic index. Under different current normal stress, the change trend of residual strength with plastic index is basically the same.(5)In the current law to be sigma ?0 < 150 k Pa, the current method to be force and residual strength may have a non- linear relationship; in the normal stress sigma ?0 > 150 k Pa, the current method to be force and residual strength has a linear relationship.(6)By the residual strength and the method to force ratios obtained the residual friction angle obtained in three different current method to the stress level, the residual friction angle are with increasing for plastic index decreases, and has the same trend. The relationship between the residual inner wiping angle and the plastic index of the 20 kinds of saturated cohesive soil can be expressed by exponential function, and the parameters depend on the current normal stress.