Experimental and numerical assessment for the roof-contacted filling effect of expansive backfill

Abstract

The effect of roof-contacted filling is a significant factor that affects the ground pressure management in the filling mining method. The expansive backfill is developed to solve the problem of the difficulties of roof-contacted filling in the open stopes with subsequent filling mining method, as well as actively supporting the surrounding rock masses by expanding its own volume and generating certain pre-stress to the roof. This paper focuses on analyzing the mechanical effects of roof-contacted filling with expansive backfill using a simulation test. Subsequently, the results of the simulation test were validated through theoretical analysis and numerical simulation. The results showed that: (1) The roof of the roof-contacted unfilling (RCU) mining room and the roof of the roof-contacted filling with ordinary backfill (RCO) mining room were both under downward stress whereas the roof of the roof-contacted filling with expansive backfill (RCE) mining room was supported by upward stress. (2) The RCU mining room led to a stress concentration in the roof and pillar, whereas the RCO mining room relieved the stress concentration in the roof and pillar. The RCE mining room did not only relieve the stress concentration in the roof and pillar, but also provide support to the roof and pillar. (3) The expansion stress generated by the self-expansion of the expansive backfill played a direct supporting role to the roof and the upper part of the pillar, and produced a positive Poisson effect to the lower filling body, which in turn provided support to the middle and lower part of the pillar. (4) Compared to RCU and RUO, the RCE enables the filling body to change from passive bearing to active support of the roof and pillar. This transition allowed more effective limitation of roof and pillar deformation while working in coordination with them to improve stress distribution within the mining room. As a result, the stability of the mining room was maintained, and the effect of roof-contacted operations was significantly enhanced.