Study on precursor information of rock instability based on displacement increments measured at multiple points

Prediction of rock failure is key in the study of rock mechanics. The physical parameters of rock such as acoustic emission, wave velocity, and resistivity undergo changes during the process of rock deformation and failure; therefore, they cannot be used to predict failure or stress–strain in the rock unit. In this study, the relationship between the variation coefficient of rock surface displacement and the peak stress is analyzed by performing physical experiments of rock uniaxial compression and the numerical simulation of heterogeneous rock fracture. In addition, a formula is proposed for determining the quasi-variation coefficient of the displacement increment measured at various points on the rock surface. The results reveal that the quasi-variation coefficient of the average displacement increment measured at multiple points is closely related to the rock instability. In the linear elastic and nonlinear plastic stages, the quasi-variation coefficient of displacement increment changes smoothly and tends to be constant. At the moment of rock instability, however, the increase is sharp. Hence, rock failure can be predicted by using the variation coefficient of displacement increment. This approach can be used as an important method for the prediction of rock mass instability or earthquake occurrence.