Internal friction resistance of saturated rocks under cyclic loading

The stress-strain loop hysteretic nonlinear behavior of a rock is generally adopted in uniaxial cyclic loading experiments. Pore fluid, cyclic loading frequency, confining pressure and bedding direction are important external variables that cause stress and strain hysteresis, energy attenuation and rigidity change of rocks. In this paper, three comparative experiments have been carried out under the Material Testing System (MTS) for the stress-strain hysteresis with different saturated fluids, the rock energy attenuation by loading different frequency stress and saturated fluids, and Young’s modulus effect for the sandstones with different bedding directions sampled from Daqing, Nanjing, Hefei, etc. Based on the results, we clarified the nonlinear elastoplastic response characteristics of saturated rocks, and revealed the nonlinear deformation mechanism induced by external factors. And the mediating role of friction resistance on internal particle contact surfaces during rocks nonlinear elastic deformation process is proved. It is inferred that the sliding friction resistance of particles in macro-cracks may be the main internal factor resulted in the attenuation and hysteresis of rocks. This paper attempts to further reveal the dynamics process of earthquakes and rock instability based on the similarity of frictional sliding between the fine-scale rock particles and the earth-scale tectonic faults.