Experimental Study of Ultrasonic Waves Propagating Through a Rock Mass with a Single Joint and Multiple Parallel Joints

Abstract

Experiments were conducted to study the relationship between the transmission ratio (TR) and nor- mal stress, joint roughness, joint number and frequency of incident waves, respectively, when ultrasonic waves pass across a rock mass with one joint and multiple parallel joints oriented normally. The ultrasonic waves were gen- erated and received by pairs of piezoelectric transducers and recorded by an ultrasonic detector. The specimens were subjected to normal stress by a hydraulic jack and loading frame. The jointed rock mass was produced by superposing rock blocks in the study. Rough joints were produced by grooving notches on the planar joints formed by sawing directly. In the case of multiple parallel joints, the overall thickness of specimens was maintained while the joint number changed. Three pairs of P-wave trans- ducers and one pair of S-wave transducers with different frequencies were, respectively, applied and all transducers emitted signals perpendicular to the joints in the experi- ment. The results indicate that TR increases with increas- ing normal stress while the increment rate decreases