The Experimental Study On The Mechanical Property Of Pisha-Sandstone

The Pisha-Sandstone is originated in dry sub-arid regions, it is a kind of sedimentary rock layers with poor diagenesis. Adhering to the typical constitutive property and special sensitivity for water of Pisha-Sandstone, which tend to have slope failure problems under conditions of wind erosion, water erosion and gravity erosion, resulting in disasters. Besides, with the enhancement of engineering constructions and scale in Pisha-Sandstone areas of south Inner Mongolia in recent years, it is of dominant importance to study the mechanical property of Pisha-Sandstone.This essay researches on the Pisha-sandstone in Jungar Banner of Erdos in Inner Mongolia, and adopts the combining method of laboratory test and field test. Experimental results indicated that the density of Pisha-Sandstone is high and, the diagenesis is relatively denser during the deposition process. It is capable of higher strength, larger permeability coefficient and lower saturated water content. But it will be easily saturated when the barely Pisha-Sandstone is exposed to natural precipitation, making itself to loss the strength easily which is responsible for the water loss and soil erosion. Through the unconfined compressive strength test conducted on Pisha-Sandstone, results showed that the sensitivity is higher and the constitutive property is stronger when the water content is small; its strength decreases with the increased water content and the compression strength becomes almost zero when the water content is saturated. Additionally, the constitutive equation of Pisha-Sandstone under condition of uniaxial compression was built, and the corresponding stress-strain curve equation was basically compatible with the Saenz model.Results for the direct shear test been applied to the Pisha-Sandstone illustrated that the shear strength decreases with the enlarged water content, the strength was lightened by more than50%when the water content was saturated. Further research shows that main influence of the water content is cohesion of the Pisha-sandstone Under influences from the low vertical load, the impact of water content on the shear strength of Pisha-Sandstone becomes increasingly significant and the effect is lightened when the water content becomes larger but, remaining drastically. Meaning while, the general trend of the cohesive force for Pisha-Sandstone depicts an increasingly lowered logarithm form with the enhanced water content. When the water content is becoming saturated, the cohesive force is close to zero. Herein, the impact of water content on the internal friction angle of Pisha-Sandstone is not significant.With the characteristic of anisotropism for Pisha-Sandstone, the influence of varies angle selections on the shear strength is also mainly behaved on the cohesion, the influence of varies angle selections on the shear strength is notable, and the force ranks last when the angle is30-60degrees; it becomes higher when the angle is0, while the90degree associated force is the highest. Accompanied with the enlargement of water content, the effect of angle selections on cohesive force is lowered and, the fovea inferior trend turns unobvious, the curve becomes a linear one when the water content is close to saturation, as well as the zero cohesion. Besides, the impact of sampling angles variability on the internal friction angle happens to be lower, with the little differences been observed for angles of30,60and90degrees separately but, been higher than the0degree one.On the basis of the tests been applied to those basic mechanical properties of Pisha-Sandstone, a scanning electron microscope test was conducted. Providing microscopic theoretical basis for the research on mechanical properties of the Pisha-sandstone, Formation of the Pisha-sandstone is observed from the perspective of micro-structure.