Dynamic mechanical response and damage evolution of cemented tailings backfill with alkalized rice straw under SHPB cycle impact load

Abstract

Dynamic disturbances such as blasting excavations cause damage to backfills. To ascertain and improve the dynamic mechanical response of backfill under frequent disturbance, single and cyclic impact load tests were conducted on cemented tailings backfill mixed (CTB)with different contents of alkalized rice straw (ARS) using a split Hopkinson pressure bar. The evolution laws of the dynamic mechanical properties and damage characteristics of CTB with the impact times and the ARS content were analyzed. The results showed that (1) The dynamic compressive strength (DCS) of CTB was improved by the ARS under single impact load with different strain rates. (2) Under the cyclic impact loads, the DCS, dynamic elastic modulus, and peak strain of CTB decreased with the increase in the cyclic impact times. Under the same impact times, the DCS of the backfill first increased and subsequently decreased with the increase in the ARS content, and 0.3% was the best content. (3) The unit volume absorbed energy of CTB was increased by the ARS and the longitudinal wave velocity (LWV) decay rate of CTB was decelerated under the cyclic impact loads. (4) The established damage evolution equation of CTB based on the LWV showed that its cumulative damage degree was increased by the cyclic impacts. Moreover, the incorporation of ARS was beneficial for decelerating and reducing the damage evolution rate and degree. The ARS was wrapped by hydration products in the CTB matrix, and its adhesion with the matrix promoted the ARS to play a bridging role, and inhibited and slowed down the development, propagation degree and propagation rate of cracks in CTB under cyclic impact. When the content of ARS was further increased, the probability of overlapping was significantly improved, which was not conducive to the adhesion between ARS and CTB matrix, resulting in the decline of the mechanical properties of CTB. The research results provide a reference for the understanding of the dynamic mechanical response of CTB with ARS under frequent blasting disturbances.