Experimental investigation of predicting points using Tangent damage factor for limestone failure

Abstract

It is difficult to predict rock cracking and failure accurately given the complex mechanical behavior of the rock failure process under uniaxial compression. Based on the Weibull statistics distribution theory, the equivalent hypothesis theory and damage theory, the damage-time-failure predicting model was established. The damage, time and stress were synthetically considered to predict the rock failure, and the process of rock failure was analyzed. In this paper, we first briefly introduced the Tangent damage factor (TDF) based on the acoustic emission parameters of two groups' experimental data. The relationship between the damage factor and load-time was indicated, and the power law relationship was obtained. The TDF model, applied to limestone, was established. On this basis, the initial predicting points (precursor) and key predicting points (instability point) were identified according to the TDF curve in the process of rock cracking and failure. The initial predicting point was approximately located at 75% of the peak strength, and the key predicting point was the peak strength point. The interval for the precursor point and the failure point, which is the TDF (kB = 0), was divided into three predicting stages: the blue predicting stage (B-E), yellow predicting stage (E-F), and red predicting stage (F-D). The experimental results demonstrated that there is a power law relationship between the damage factor and load-time. The damage factor curves verified the phased characteristics for rapid growth-stable growth-sharp growth-stability. Identification of the predicting points based on the abnormal change behavior of the TDF in the process of rock failure is very important forewarning information. The experimental results indicated that this is a meaningful study for predicting rockburst. The established forewarning model and proposed grading prediction method contributed to predicting hierarchically rockburst hazards in the field.