Experimental Research On Shear Failure And Surface Morphology Characteristics Of Sandstone

In the engineering of slope treatment,hydraulic development,tunnel construction,mining and so on,joints connect is one of the main failure modes of the rock mass because of shear loading.As is known to all,the shear failure characteristics of rock are influenced by various factors,such as it’s type,size,moisture,loading rate and so on.In practical engineering applications,due to the existence of crustal stress,it’s distribution characteristics plays a crucial impact on stability of rock mass.In addition,the influence research of water on the shear failure characreistics of rock mass also can provide a theoretical basis for practical engineering application because of the existence of surface rain and groundwater.Therefore,experimental study is made on shear failure process of sandstone,their mechanical properties and surface morphology under shear loading condition by independent developmental shear-flow coupling test device for coal or rock and three-dimensional scanner.Simultaneously,it is also researched on their mechanical properties and surface morphology of sheared sandstone under the different normal stresses,the different moisture statesand the different pore water pressure in shear loading.The main results obtained are as follows:(1)With the increase of normal stress,the shear strength and the peak shear deformation increase,but reduce of the peak normal deformation.Due to the limitation from the normal stress,the crack extension range in sandstone surface is narrower,and the number of secondary cracks are little.In addition,with the increase of normal stress,the height distribution of the fracture surface show a better Gaussian distribution,and the waviness and roughness of the shear fracture surface are smaller.(2)Due to the softening effect,lubrication and water wedging action from the water pressure,with the relative increase of moisture content,the shear strength,the peak shear deformation and the peak normal deformation of sandstone decreases,the surface crack distribution is more smooth,the number of secondary cracks are little,and the roughness of shear fracture surface decreases.(3)Pore water pressure can effectively reduce the adhesion between the mineral particles,weak the shear strength of sandstone,and the higher the pore water pressure,the weakening effect is stronger,the lower the shear strength of sandstone,the smaller the peak deformation,the lower the roughness coefficient of the fracture surface,the more smooth the fracture surface.(4)Based on the comprehensive analysis of the sandstone specmens after all the compression shear test,and combined previous research results,summed up a set of relative complete method of shear failure analysis.It’s mainly focused on three aspects,such as the surface rack distribution of the damaged specimen,the feature of the cross section fluctuation and the characterization of the morphology characteristic parameters.