Estimation of rock wall closure generated by stope excavation underlying the sill mat made from cemented backfill

Underhand cut-and-fill mining is necessary when rock walls and the orebody are of poor quality or when rock bursts are of high concern. Sill mats made from cemented paste backfill must be constructed before excavating the underlying stope. Large rock wall closure associated with the excavation underneath can then be expected. This phenomenon has already been confirmed by numerical modelling and field observations. The rock wall closure can then affect the stability of the base-exposed sill mat. Thus, it is a critical issue to determine the rock wall closure induced by the excavation underneath the cemented backfill (i.e. sill mat). In this study an analytical solution for determining the rock wall closure associated with excavation underneath is first presented. After that the proposed analytical solution is validated by numerical results by considering different stope geometries, mine depths, lateral pressure coefficients, and the mechanical properties of the rock mass and sill mat. The proposed solution paves the way for estimating the required strength of the sill mats subjected to significant wall closures.