Investigation of failure mechanism of cement-fiber-tailings matrix composites using digital image correlation and acoustic emission

In this study, the failure mechanisms of cement-fiber-tailings matrix composites (CFTMCs) in unconfined compression strength tests were investigated using the digital image correlation (DIC) and acoustic emission (AE) techniques. The results indicated that the addition of polyacrylonitrile fiber to the backfill could optimize the microstructure and thus improve the mechanical properties of the material. The fiber exerted a significant restraining effect on the expansion of internal fractures in the backfill. Using DIC, it was observed that the addition of fibers could eliminate the strain concentration regions in the material to a certain extent and reduce the transverse deformation of the main fracture. In addition, the AE characteristics of cement paste backfill (CPB) and CFTMC differed significantly; the AE cumulative count of CPB decreased significantly after the yield point, whereas that of CFTMC increased abruptly after the stress peak. Furthermore, the degree of fluctuation in the AE cumulative count of the samples increased with the decrease in the cement / tailings ratio, and the destruction area became more apparent as the tailings content inside the CPB decreased. These conclusions can serve as an important reference for stability research on goafs filled with CFTMC.