ABSTRACT

Although numerous studies have been conducted to investigate wave propagation cross intact rock and rock mass, effect of rock damage on wave propagation has not been investigated in details. In this paper, damage evolution of granite under static compression and its effect on ultrasonic P-wave propagation in granite were experimentally studied. During testing, intact granite samples were compressed to the constant loads using a uniaxial compression machine. Meanwhile, the acoustic emission (AE) activities in the sample were recorded to quantitatively define the damage. During compression, ultrasonic P-wave velocity and transmission in the tested sample along the loading direction were measured at different loading levels. It is found that AE activities were inactive, indicating low damage degree, when the stress is lower than 60% of the uniaxial compressive strength (UCS). When the load approaches the UCS, a large number of AE counts were continuously generated and the damage degree significantly increased. With increasing loading and damage, P-wave velocity and the amplitude of the transmitted wave significantly increased prior to about 80% of the UCS, attributed to few damages and closure of pores and fissures. When stress approaches the UCS, the wave slowness and attenuation were enhanced, due to the damage evolution and accumulation. The experimental findings facilitates to better understanding of the relationship between damage evolution and ultrasonic P-wave propagation in rocks.