Effects of lateral cyclic loading on compression behaviours of granular waste rocks for backfilling to reduce environmental pollution.

Granular waste rocks filled in goaf can replace coal seams to support roofs, thus reducing the extent of overlying strata movement, and thus reducing the environment damage caused by coal mining. To better to control the compression-induced deformation (CID) of waste rocks for backfill (WRBs), a loose material, it is feasible to apply lateral cyclic loads on granular waste rocks in advance. In order to study the effect of lateral cyclic loading on granular waste rocks, by utilising pre-lateral cyclic loading and axial loading, the deformation of granular waste rocks under load was tested on a compression simulation experimental platform for solid backfill materials. Furthermore, the changes in displacement, stress and mass of granular waste rocks during lateral cyclic loading were attained. The test results showed that (1) the loading stress progressively increased with the growth of the loading displacement, in which the rising process was divided into three stages according to the rate of loading. (2) With the increase in number of loading cycles, the rate of increase of stress in stage I increased and the stress reached increasingly higher levels; at the same time, stage II was gradually shortened. Eventually, only a single stage prevailed as the stress rapidly reached its preset maximum value, and the final displacement of the samples gradually declined. (3) The axial stress-strain curves of the samples exhibited a quasi-exponential relationship. Through lateral cyclic loading, the relative density of WRBs was significantly improved, and their deformation resistance was strengthened. (4) During backfill mining, lateral cyclic loads were applied to granular waste rocks, which improved the bearing capacity thereof and reduced strata movement and surface subsidence. This is beneficial to the protection of the surface environment and surrounding buildings.