Experimental Investigation of Propagation and Transmission of Compressional Stress Waves in Cemented Paste Backfill

摘要

A split Hopkinson pressure bar (SHPB) was used to characterize the propagation of high intensity large strain compressional waves through cemented paste backfill (CPB). The effects of curing age, cement content, and degree of saturation on stress refraction at interfaces, velocity of propagation, and internal damping in CPB were investigated. The results show that a smaller portion of the incident stress wave is refracted at the CPB interface in unsaturated specimens in comparison to those in a near fully saturated condition. Increased refraction ratios and velocities of propagation as a result of increased curing age and cement content were mainly observed in unsaturated specimens. In addition, the effects of degree of saturation on stress wave propagation in unsaturated material seemed negligible. The compression wave propagation velocity in the SHPB was also compared with small strain velocities found by means of ultrasonic wave measurements. The measured small strain wave velocities were found to be consistently smaller than the large strain velocities found in the SHPB. Similarly, the small strain elastic theory was found to underpredict the transmission ratios at CPB interfaces. Thus, it was proposed to account for correction factors by accounting for the changes in density and constrained modulus under high amplitude and short duration compressive waves. The coefficient of attenuation remained practically unchanged at different curing ages and was shown to significantly decrease near saturation.