Experimental Study On The Strength Of Slip Soil

The natural phenomenon that the soil or rock mass on the slopes slide down along the slope integrally under the rivers,rain water and groundwater activity,artificial slope cutting,earthquake and other factors is landslide.The landslide is one of the most serious consequences of geological disasters because of the quantity and the risk for a long time.The slide zone soil always accompanied with the occurrence of landslide,and the residual strength is the key to strengthen the stability of soil slope and prevent landslide research effectively.And conventional field in situ test,repeated direct shear test,as well as the conventional triaxial test are to be limited in the measurement of residual strength due to reasons such as instrument manufacturing mechanism.It is needed to use the ring shear apparatus to measure the residual strength for guiding the engineering practice.This paper is aimed at exploring the characteristics of deformation and strength about clay in different states(consolidation state,water content),and different conditions(effective normal stress,shear rate,shear mode and over-consolidation ratio)by the American GCTS SRS-150 dynamic ring shear apparatus.The main content and research results are as follows: 1.The influence of moisture content Three groups of ring shear test were carried out with the same shear rate,different moisture content(20%,26%,30%)to get the corresponding shear stress—shear strain curve.It was found that it presents obvious softening phenomenon that with the increase of the shear displacement,stress-strain curve firstly rise to the peak,and then gradually decline until reach the residual strength and remain unchanged;Peak strength and residual strength both have close relationships with water content of soil samples.They increased with the increase of water content decreases,and soil softening phenomenon is more obvious with the higher water content;Effective cohesion of the soil increased with the moisture content,but it is unconspicuous that the internal friction angle is affected by the moisture content.2.The influnce of shear rate The ring shear test under the same moisture content,different shear rate(0.01 mm/s,0.04 mm/s,0.1 mm/s,0.4 mm/s)were carried out.The study found that,under the large shear rate,the strength of the soil increased with the increase of shear rate;The greater the shear rate,the greater the degree of softening soil;To achieve stable soil residual strength value,the greater the displacement is needed;Peak intensity change of soil is mainly due to the effective cohesion has changed.3.The influnce of consolidation ratioTaking shear test of two different soils,IP = 7 and IP = 18,the over-consolidated for 1,3,5,7.The study found that,the higher the plasticity index,the higher the degree of softening of the soil.Basic softening degree increases with the increase of over consolidation ratio;the change of the residual strength of the soil in high plasticity index is unobvious with the increase of over consolidation ratio,compared with the plastic index.4.The influnce of cyclic loadingBy means of constantly trying with multiple sets of sample,the realation between the strength cyclic loading with the strength is found.