Mechanical behavior and meso-degradation mechanism of cemented paste backfill under the coupled effect of disturbance damage and dry-wet cycles

To study the coupled degradation effects of disturbance damage and dry-wet cycles on backfill, cemented paste backfill (CPB, a mixture of coal gangue, fly ash, cement and water) samples with disturbance damage were prepared by cyclic disturbance loading tests. Subsequently, uniaxial compression tests were performed on CPB samples subjected to both disturbance damage and dry-wet cycles. Combined with the discrete element method, this study systematically explores the mechanical behavior and meso-degradation mechanisms of CPB under the coupled action of dry-wet cycles and disturbance damage. The research shows that: ①The cyclic disturbance loading will cause disturbance damage on CPB samples, and as the number of disturbances increases, the degree of damage gradually increases, and the two are exponentially related. ②There is a dry-wet cycles threshold value (5 times) for CPB samples. Below the dry-wet cycles threshold, the strength of CPB increases gradually with increasing dry-wet cycles. Above this threshold, however, dry-wet degradation occurs, and the elastic modulus degrades more significantly than the peak strength. ③The impact of disturbance damage diminishes with increasing dry-wet cycles. ④Under the coupled effect of disturbance damage and dry-wet cycles, the bind force between particles in CPB samples decreases, the energy absorption and storage capacity decreases, the frictional energy consumption increases, internal pores and microcracks initiate and develop, and the internal structure changes from dense to loose porous. The research results can effectively promote the development and application of backfill mining technology in coal mines.