Measurement of distribution of rock joint stiffness based on active ultrasonic excitation

Goodman proposed to use the joint stiffness to characterize the topological behaviors of complex rock joint interfaces and provide quantitative values for them, without measuring and analyzing the geometric parameters such as roughness and contact area of joint interfaces in detail. However, it is difficult to measure the stiffness of rock joints at present. Therefore, the piezoelectric ceramic transducer is used to excite the elastic waves of the intact granite plate specimen and the cracked granite plate specimen in the laboratory environment. At the same time, the scanning laser Doppder Vibrometer is used to monitor propagation data of the elastic waves in the plate. On this basis, the collected signal data of wave fields are processed by filtering, interpolation, integration, etc., and the distribution of joint stiffness is calculated based on the Schoenberg linear sliding model. Then, the joint stiffness is used to parameterize the contact behaviors of rock joints, which further proves the feasibility of ultrasonic characterization of whole rock joints. By using the full-field waveform data, the interface contact behaviors of rock joints are clearly revealed, which lays a foundation for further exploring the relationship among rock joint geometry, pore sizes, interface properties and seismic characteristics.