Experimental study of the ultrasonic and mechanical properties of SRM under compressive loading

Experiments were conducted to investigate the relationship between the ultrasonic pulse velocity (UPV), transmission ratio (TR), attenuation coefficient (AC) and mechanical properties of soil and rock mixture (SRM) with different rock percentage, under uniaxial compression. Cylindrical SRM specimens (50 mm diameter and 100 mm height) with rock block percentage of 20, 30, 40, and 50 % were produced to perform a series of Uniaxial Compressive Strength (UCS) test. The ultrasonic wave was transmitted and received by a P-wave piezoelectric transducer (130 kHz) and the ultrasonic travel time and amplitude were recorded by an ultrasonic detector during the whole deformation process of specimens. From the test results, the UPV decreased and AC increased with the increasing rock percentage for all specimens by ultrasonic inspection before UCS test. The failure mechanism of all specimens showed splitting-sliding mixed pattern, macro-cracks have a direction of 0–10° parallel or sub-parallel to normal stress, and UCS decreased with increasing of rock percentage. In addition, the UPV and TR have fluctuation growth trend with increasing of axial stress while the increment rate decreased gradually. The statistical correlations between UPV and TR and axial stress are presented and discussed. Moreover, the relationship between ultrasonic parameters and axial stress for soil and rock specimens were also discussed. These results confirm that the ultrasonic and mechanical properties of SRM are closely related to rock percentage. As a special geomaterial, the mechanical properties of SRM are different from rock and soil; this can be further confirmed by ultrasonic tests.