Experimental Study On Direct Shear Creep Characteristics And Long-term Strength Of Red Layer Sliding Zone Soil In Southern Hunan

a large number of slope engineering projects show that：red layer slope instabilityis due to the shear creep damage of the sliding zone. Therefore study the shear creepcharacteristics of sliding zone and its long-term strength is particularlyimportant.Because of red soil layer with the characteristics of soft and hard，the weakinterlayer is the material basis for the landslide formation. the change of the softinterlayer water content has a obvious impact on the stability of slope.Red bed slope isoften the result of artificial excavation and drainage problems,eventually led to theformation of landslide slope imbalance.There have been many researchers on therheological characteristics and long-term strength of sliding zone to do a lot ofresearch work [19],But the research or public reports specific to the shear creepproperties of sliding zone southern hunan red layer are rare.shear displacement vstime curves and shear displacement vs shear stress curves are obtained by studying thecreep characteristics of red-layer sliding soil after gradingly burdenning shearforce under various vertical loads via direct shear creep experiment, which will beused as the technical bases in choosing the long-term strength parameters andcalculating slope deformation. The main research contents and results are as follows:(1) Through the direct shear creep test on a series of the red layer of slidingsoil, discusses the creep properties of soil under different vertical load and moistureconditions. The test results show that: Because of the red layer sliding rock crushing,and the water along the red layer sliding belt fissure infiltration to the sliding zone, thesoftening of sliding soil, accelerated the development of the shear creep, when theshear stress reaches the shear strength of slip zone long-term limit and the soild under the certain condition of moisture content, if the vertical load smaller, sliding soil ischaracterized by sudden cut broken. When the vertical load is large enough, the slidezone soil is a constant acceleration creep development. When the red layer slidingzone soil under the condition of certain moisture content and the vertical stress, withincreasing shear level, the direct shear creep deformation is increased, The wholecreep process experienced three stages, the transient creep, creep and the acceleratedcreep. When the red layer sliding zone soil under the condition of certain shear stressand the vertical stress, with increasing moisture content, the feature of nonlinearrheological is more obvious, and the direct shear creep deformation is larger.(2) Through the direct shear creep test results in the red layer of sliding soilshear stress-shear displacement curves,It is concluded that the curve change rule andthe characteristic. The rheological model that to experience the three rheologicalparameters: creep deformation rate, coefficient of viscosity and shear modulus. Theresearch showed that the red layer sliding zone shear stress-shear displacementisochronous curve showed a nonlinear rheological characteristics.It performance foralong with increasing shear stress and time, the curve will gradually move closertoward the strain axis. Under the certain condition of moisture content, the change ofthe shear modulus of the sliding zone is inversely proportional to the change of timeand shear stress, Under the certain condition of shear stress; the change of the viscouscoefficient of the sliding zone is proportional to the change of vertical load; Under thecertain condition of vertical load; the change of the viscous coefficient of the slidingzone is proportional to the change of shear stress.(3) Combination of the long-term strength theory and the failure criterion whichcome from the creep test, Established the long-term strength equation in the form ofpower function. The equation describe well the three soil creep state of theexperienced under long-term load, to complete the simulation of the red layer ofsliding soil long-term strength characteristics, For red layer slide of slope deformation,strength and stability problems of analysis provides a theoretical basis.