Abstract
The measurement of rock joint parameters is a hotly debated and difficult problem in rock mechanics. Joints have great influence on the propagation of stress waves in rock mass. Since the multiple reflections of stress waves propagating inside the joints is not considered accurately, the reflection wave shape cannot be obtained by using a discontinuous displacement model to describe the deformation characteristics of joints. A joint is regarded as a rock using the first analysis of the stress wave transmission in the course of a single joint and the propagation law of a reflection wave. For rocks orientated in the same direction with the same type of wave superposition, stress wave parameters can be established through the multiple reflection effect of a single-joint analysis model. Further to this, analysis using an extended single-joint model can estimate a stress wave under the condition of a vertical incidence group parallel strata analysis model. Taking a single macro-joint as an example, a measuring line is arranged in the normal direction of the joint, and two measuring points on both sides of the joint are arranged in a line to record the waveforms of the incident and transmitted waves. According to the established single-joint analysis model, the calculated waveform of the incident side measuring point is calculated by using the measured waveform of the transmission side measuring point, and the measured waveform of the incident side measuring point is compared with the measured waveform of the incident side measuring point, and the joint elastic parameters with the minimum error are obtained by using the principle of least square method. Six tests were carried out through joints with a thickness of 0.04 m. The results show that the primary wave (P-wave) and secondary vertical wave (SV wave) velocity of joints obtained from many tests have good consistency, which indicates that the joint analysis model has good stability, and the test solution of joint elastic parameters based on the model is reliable.
Highlights
Due to the stratification of rock, multiple transmission and reflection effects will occur when a stress wave passes through a rock formation
According to the law of transmission and reflection of a stress wave through a single joint, the waves in the same direction and the same type are superposed in this article, and the analysis model of stress waves passing through single-joint rock is established
The macro-joint model of stress waves passing through a group of parallel jointed rocks is proposed
Summary
Due to the stratification of rock, multiple transmission and reflection effects will occur when a stress wave passes through a rock formation. According to the superposition principle, the relationship between the waveforms in a single-jointed rock mass can be obtained: The outgoing P wave u4 in rock layer 1 is equal to the FIGURE 2 | Incidental, reflective, and transmitted stress waves at interfaces. For the actual rock mass with multiple parallel joints, as shown, the method of calculating the total transmission and reflection coefficients of a single-jointed rock mass when the P wave incident is vertical can still be generalized. According to the spherical diffusion effect of the stress wave excited by the point source in the rock mass and the spectrum of the transmitted wave at measuring point 2, the calculated spectrum of the incident and the reflected wave can be, respectively, obtained. By substituting the average calculated wave velocity into Eqs. 25 and (26), the joint elastic modulus and Poisson’s ratio are 6.03 GPa and 0.19, respectively
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
