The Experimental Research On The Shear Mechanical Property Of Pisha-Sandstone With Different Particle Sizes

Pisha-sandstone is part of continentally clastic rocks. Because the overburden is thick and its low pressure, the pisha-sandstone’s diagenetic degree is low-. cementation is poor,the biggest feature is when meet water the pisha-sandstone become mud and when meet wind the pisha-sandstone become sand. The soil erosion is very serious in pisha-sandstone area. Recent years, the construction of water conservancy projects is increased in pisha-sandstone area of southern Inner Mongolia,the studying on mechanical of pisha-sandstone is very important. At the same time, in the calculation of the stability of landslide,before sliding many landslides generally form a sliding surface and the shear strength of sliding surface has been reduced to residual valua, so the residual strength also must be studied; Considering to the moisture content is extremely important and the anti-erosion of diffrernt particle sized have significant difference; I conduct the experiment on iteration shear properties of pisha-sandstone and discuss the changes of shear strength and residual shear strength under distinct particle sizes and different water content.For the first in shear, different sizes samples stress-strain curves are obvious reaching peak. The shear strength of particle size 0.5-0.25mm specimen is lowest and the engineering property is worst. The large particle size of sample’s particle crush is obvious with high water content the relative coarse particles are broken easily. The tiny particle are increased significantly when the water content is increased.With water content increased the shear strength of different particle sizes decrease linearly. In the low normal stress, the water contents have intense influence on shear strength. The cohesion and the angle of internal friction decrease when water content increase, but the cohesion decrease more. The residual cohesion decreased linearly when water content increase under three particle sizes. Particle size of O.5-O.25mm mutate obvious.At the beginning of the shear stage, the specimen exhibited reduction character; with the shear displacement increased, the specimen shows dilatancy character. Using R.Simon shear dilatancy model has some defeats.It can not describe the initial shear shrinkange. In this paper, using SAS software to carry out regressing analysis conduct a new dilatancy. Experiment and fitted values have a good degree fitting.