Ring Shear Test Condition Of Slide Zone Experimental Study The Mechanical Behavior Characteristics

Slip soils are important for landslides research and control design. The mechanical behavior closely related to the occurrence and development landslides.Therefore, the research on the physical and mechanical properties and the mechanical behavior of the sliding zone soil has played an important part in landslides research and prevention.Scholars both at home and abroad on the study of the sliding zone soils are mainly concentrated in the geological characteristics of the slide zone soils, the composition, structure, physical properties and long-term strength. Their research object is the most common clay. However, the sliding zone soil has strong regional characteristics, general clay is not universal and representative. Therefore, study separately according to different sliding zone soil is essential. At present, the research on the nearly horizontal strata landslide of the sliding zone soil is less. This soil is commonly developing in Sichuan Red Basin area. By integrating the existing literature related to slide soil physical and mechanical properties, acquaintancing the current research status and existing problems on sliding zone soil, this paper has the nearly horizontal strata landslide of the sliding zone soil in Sichuan Red Basin area as its research object and the KuaLiangZi landslide as the representative of this type of sliding zone soil. A further research was done for the mechanics behavior and properties of the sliding zone soil through the lab test, it can enrich the development the research theory and the content of sliding soil.The main research contents and achievements in this paper can be summarized as follows:(1) Based on the characteristics of strength of slip soil laboratory ring shear test,it shows that the shear strength of landslide soil increases with the normal stress, Soil particles on the shear plane is aligned along the shear direction easily; the peak strength of sliding zone decreases as the shear rate increases, the residual strength of convergence in the 5% regions. From the view of microstructure, the formation process of shear deformation and orientation of mineral grains even rearrangement process, the normal stress and the shear rate and the orientation arrangement of soil particles on the soil failure will not affect the shear surface.(2)The water- rock mechanics of the type of landslide is mainly generated hydrostatic pressure caused by impounding in the crack of the trailing edge, and uplift pressure produced by permeating which ascribes to the water in the crack across the impermeable mud rocks layer. It approaches the shear plane of the sliding zone soil has impact on creep property in the sliding surface under the action of uplift pressure and shear stress across using the ring shear apparatus,the test results show that after sliding zone formed in the shear plane has still creep property, and it has three phases,which are creep deformation, stepped deformation and accelerating deformation; For the same shear surface, when the effective normal stress is invariability, and the RCSR increases to 1.019, the shear stress is higher than the residual shear strength1.54 kpa at the conditions, meanwhile the sample has stepped into accelerating deformation damage; but if the shear stress is constant, and making uplift pressure increasing to 100 kpa, the sample will fast sliding along the shear plane, which reflects the sensitivity of the creep deformation is higher on the condition of shear stress, and when the fissure water level is low at the trailing edge of landslide, it consists with the situation that the shear surface is still sliding.(3)Residual strength of the sliding zone has complex effects on sliding rate. It studies the change of residual strength under the different shear rates. The results show that: shear surface will immediately appear a peak intensity under the tiny displacement, and along with the increase of the shear displacement, the peak intensity will be slow attenuation to the residual strength, what is the cause of the phenomenon? And it may be due to the improvement of pore water pressure at the shear band. Since it is drained shear test, the pore water pressure is not the main influencing factors, but the soil structure on the shear zone is disturbed, as well as it changes the shear mode that is relative sliding of soil particles is directional alignment,which changes the friction between soil particle, at last, when the slip rate is increasing, the residual strength and effective angle of internal at the shear surface will decrease.(4)At first the soil in slide is reshaped, and then the samples do an experiment about soil-water characteristic curve under full range of suction across using volumetric pressure plate method, filter paper method and vapor equilibrium technique with saturated salt solution. The results shows:in different suction range,the matrix suction has obvious diversity along with the change of moisture content,when the moisture content is from saturation to30.01%, the matrix suction is slow growth, however, when the moisture content decreases to10.58%, the growth of the matrix suction is obvious faster.(5)It makes unsaturated soil samples according to the filter paper method, the paper discusses the influence of different saturation on strength of sliding zone soils.Experimental results show: under the condition of long shear displacement, the water in soil moves to shear band. When the strength decreases to the residual shear strength,shear zone of moisture content increased obviously; Saturation is mainly through the matrix suction to impact on the strength of the sliding zone, the overall trend of the saturation is decrease with the increase of the strength soil. When the matrix suction changes in 0 ~ 0.1MPa, the strength of the soil has not obvious change; but when the matrix suction continues to increase, the soil strength significantly increase with the increase of matrix suction. Unsaturated soil sliding zone soil strength envelope above the saturated soil, unsaturated soil residual internal friction Angle is bigger. Unsaturated slip zone soil of strength envelope is above the saturated soil, and unsaturated soil of residual internal friction angle is bigger.