Experimental Research On Characteristic Of Deformation And Dissipated Energy Of Rock Under Cyclic Loading Conditions

In the construction and service stage of geotechnical engineering, rock mass often encounter the effect of cyclic loading and mechanical property of rock mass under cyclic loading is one of important influencing factors of long-term stability of geotechnical engineering. Therefore, it is of great significance to systematically study the evolution of deformation and damage of rock under periodic loading.In this paper, sandstone obtained from the Three Gorges Reservoir (T3xj) are studied on the characteristic of deformation and damage under cyclic loading (including uniaxial cyclic loading, triaxial cyclic loading and cyclic pore water pressure) by rock mechanics test system MTS815 and RLW-2000M triaxial creep testing machine. Based on analysis of evolution of hysteresis loop curves of sandstone under cyclic loading, the energy evolution of dissipation and release of rock specimens are also discussed. The conclusions are as below:In uniaxial and triaxial cyclic loading, with the increase of cycle number, stress– strain hysteresis loop curves show the characteristic of sparse to dense and the residual strain is gradually decreasing and become stabilized. In cyclic pore water pressure, the development of each axial effective stress– train hysteresis loop and horizontal effective tress– transverse strain hysteresis loop are clockwise and show a law of four stages.On the other hand, energy dissipation and release of sandstone specimen has been described though the use of theory of energy principle. It has been found that in uniaxial and triaxial cyclic loading, dissipated energy per unit volume of the completion of every cycle is gradually decreasing with the increase of cycle number, which means that the dissipate energy in rock specimen after the completion of each cyclic loading. However, in the cyclic pore water pressure, dissipated energy per unit volume of the completion of every cycle is gradually increasing with the increase of cycle number. In the initial stage of cyclic pore water pressure, dissipated energy per unit volume is negative, which shows that sandstone specimen releases energy to outside. While with the increase of cycle number, dissipated energy per unit volume are gradually moving to zero and has the trend to be positive, which means that sandstone specimen dissipates energy.