Study on mechanical properties and failure characteristics of sandstone under cyclic loading
In order to study the mechanical properties and failure characteristics of rock under cyclic loading,the sandstone samples were subjected to conventional triaxial loading under different confining pressures and equal amplitude cyclic loading and unloading tests under different stress levels(peak stress 40%,60%and 80%).The results show that under conventional triaxial loading,the strength of sandstone increases with the increase of confining pressure,and the elastic modulus remains basically the same.Under the same confi-ning pressure condition,the strength of rock sandstone decreases with the increase of the upper limit stress level.The failure mode of the specimen is dominated by shear cracks,and transverse or vertical tensile cracks are gen-erated in local areas.During the cyclic loading and unloading process,the loading and unloading deformation modulus of sandstone maintain a strong consistency.Under the same stress level,the loading and unloading de-formation modulus increase with the increase of confining pressure.Under the same confining pressure and differ-ent stress levels,the unloading deformation modulus still has good consistency on the whole,and the loading de-formation modulus increases slowly.Under the same stress level,the first relative residual strain of rock samples under cyclic loading and unloading has a tendency to increase with the increase of confining pressure.
rock mechanicssandstonemechanical activation behaviorresidual strain
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