Mechanical Performance of Confined Consolidation on the Strength Development of Cemented Paste Backfill

The mechanical performance of cemented paste backfill (CPB) placed in deep stopes often differs from laboratory-predicted performance, and the strength of CPB is generally determined to the uniaxial compressive strength (UCS) after the predetermined curing ages in laboratory. However, in situ backfilled stopes, the CPB is enclosed by the orebody and surrounding rocks usually, and the mechanical performance of CPB should not only be determined by the UCS. To investigate the mechanical performance of CPB in deep stopes during long-term service, the physical and mechanical conditions of CPB in situ backfilled stopes were simulated by the confined high-stress consolidation (CHSC), and the microstructure of CPB made by scanning electron microscopy was analyzed, and the strength regeneration mechanism of CPB was investigated from the microscopic point of view. The results showed that the strength of CPB in deep stopes could be excited to various degrees during long-term service, and the degree of excitation was closely related to the curing ages of CPB. The degree of excitation of the CPB strength was determined by the maximum confined consolidation stress, and the consolidated CPB was more beneficial to its supporting role in engineering. The macroscopic strength of CPB after CHSC can be increased by the increase of bond strength at the interfacial transition zone and the improvement of overall compactness of CPB. The re-filling and re-cementation of micro-cracks result in the strengthening of CPB during the re-curing ages. Compression consolidation (primary consolidation) and chemical consolidation (sub-consolidation) of CPB in the backfilled stopes occur simultaneously, and this is obviously different from the process of the compression consolidation of soil.