Experimental study for the effect of joint surface characteristics on stress wave propagation

Induced seismicity might occur during underground energy and resource exploitation. Seismic waves usually attenuate during propagation across rock joints. Joint surface configuration parameters such as the joint roughness coefficient (JRC) and joint matching coefficient (JMC) play an important role in affecting stress wave propagation and dynamic property. An experimental study was conducted by using the modified Split Hopkinson Pressure Bar (SHPB) apparatus to reveal the influence of surface characteristics (i.e., JRC and JMC) on wave propagation quantitatively. The two bars of the SHPB apparatus were fabricated from high-strength gypsum. Each specimen has an artificial joint and consists of two parts produced by 3D printing. The effect of JRC and the combined effect of JRC and JMC on wave propagation and the dynamic mechanical property of joints were analyzed. The incident, transmitted and reflected waves were recorded from the strain gauges. Based on the basic theory of SHPB tests, the transmission coefficients, the stress-strain relationships and the specific stiffness of joints were obtained. According to the test results, both JRC and JMC affect stress wave propagation across joints and the joint specific stiffness to a significant extent. The results show that the transmission coefficient and specific stiffness decrease with increasing JRC (e.g., JMC = 1). In addition, for specimens with a given JRC, the transmission coefficient and specific stiffness decrease with the decrease of JMC.