Experimental Study of the Fatigue Deformation of Rock Samples under Cyclic Loadings

A series of laboratory cyclic loading tests on rock samples with constant loading rates under different deviator stress levels are performed.The relationships among the axial strain,radial strain,bulk strain and cycle index under different deviator stress levels are evaluated.The characteristics of fatigue deformation of the rock samples subjected to cyclic loading are then analyzed.The results indicate that the axial strain,radial strain,bulk strain and deformation modulus remain constant with the increasing cycle index under the deviator stress of less than 50MPa.A diverge tendency can be observed if the deviator stress is greater than 50 MPa.Due to the increasing in number and the dilation of cracks in the samples,the average deformation modulus under a deviator stress of 80MPa is larger than the one under 110MPa.Under different deviator stress,the average deformation modulus will reduce with the increase of the deviator stress.