Shear Failure Mechanism and Acoustic Emission Characteristics of Jointed Rock-Like Specimens

Abstract

Evidence indicate that the stability of rock mass is highly associated with the shear behaviours of jointed surfaces under the effect of in situ stress conditions. Understanding the shear failure mechanism of jointed surface has great significance for tunneling and drilling engineering. Direct shear tests were conducted on jointed rock-like specimens to investigate the influence of joint roughness and normal stress on shear failure characteristics. In the present study, regular triangular sawtooth was produced to simulate different asperities. Based on the direct shear test, the specimens exhibited four types of failure modes: damage tend to occur on the sawtooth tips under low normal stress; whereas damage occurred on a large scale under high normal stress; a localized region of the sawtooth was worn when the dilation angle was small; meanwhile the sawtooth tips or base were cut off when the dilation angle was large. In addition, Acoustic Emission (AE) technology was adopted to synchronously monitor the development of cracks during testing. Further attempt has been carried out to simulate the crack initiation, propagation and coalescence using Particle Flow Code (PFC). The numerical model has successfully verified and explained the crack behaviors determined by the shear failure mechanism in the physical test. Additionally, the irregular profile was introduced in the PFC, it was found that the failure behavior in sawtooth profile has established a good conclusion to fully understand the failure mechanism in the irregular profile. This work can provide some reference for evaluating the behavior of underground engineering composed of jointed rock masses during the shearing.

Investigation of the Multi-Scale Deterioration Mechanisms of Anhydrite Rock Exposed to Freeze–Thaw Environment

“…Ban [41] pointed out that due to the substantial homogeneity of sandstone, the maximum horizontal tension strain occurs at the center of the specimen, and the failure mode is relatively simple, which is a central crack connecting the upper and lower loading points in an approximate straight line. The anhydrite rock disc sample studied in this article exhibits multiple cracking forms because there are many natural joints in the anhydrite rock.…”

Investigation on acoustic emission characteristics of fault stick-slip under different lateral pressures

“…An increase in D qmax and Δ α indicates that the multifractal characteristics of the AE spectrum are gradually enhanced, and the difference between the dominant and nondominant frequencies gradually increases, which leads to increased inhomogeneity. This might be because as the lateral pressure increases, the fracture asperities increase, and the number of cracks increases correspondingly 53 , leading to a gradual increase in and concentration of dominant frequency amplitude points. The multifractal parameters of the AE spectrum differ greatly under different lateral pressures, but the dynamic variations in the multifractal parameters are similar.…”

Investigation on Acoustic Emission Characteristics of Fault Stick-Slip Under Different Lateral Pressures

“…The increase of Dqmax and Δα indicates that the multifractal characteristics of the AE spectrum are gradually enhanced, and the difference between the dominant and non-dominant frequencies gradually increases, which leads to increased inhomogeneity. This might be due to the fact that as the lateral pressure increases, fracture asperities increase and the count of cracks increases correspondingly [43] , leading to a gradual increase and concentration in dominant frequency amplitude points. The multifractal parameters of AE spectrum differ greatly under different lateral pressures, but the dynamic variations of multifractal parameters are similar.…”