Numerical Investigation of the Stress Distribution in Backfilled Stopes Considering Creep Behaviour of Rock Mass: Fid-Bau Portal

Numerical Investigation of the Stress Distribution in Backfilled Stopes Considering Creep Behaviour of Rock Mass

Qi, Chongchong / Fourie, Andy

Abstract Evaluating the interaction between backfilled stopes and the surrounding rock mass is a vital issue during secure backfill application and stope stability analysis. With the increase of rock mass complexity and mining depth, weak rock masses and high in situ stresses are increasingly encountered, emphasising the consideration of the creep behaviour of the rock mass (CBRM). In this paper, a modelling framework was proposed by considering the CBRM and the time-dependent characteristics of backfill (e.g., increasing stiffness and cohesion with time). A generic study was present to investigate the effect of the CBRM on the stress distribution in the backfilled stope. In the generic study, a reference case was investigated in detail followed by an extensive parametric study. Furthermore, the proposed modelling framework was applied to an engineering instance, namely, the Baixiangshan Iron Mine, to verify its robustness. The generic study shows that the horizontal stress was much larger than the vertical stress in the backfilled stope at day 21 and the stress was transferred from the rock mass to the backfill (‘squeeze-induced stress effect’). The horizontal displacement of rock mass was responsible for the long-term stress development in the backfilled stope. Backfill parameters and backfill delay had a strong influence on the stope stress development while the influence of backfill gap was mainly around the upper part of the backfilled stope. The engineering application in Baixiangshan Iron Mine indicates that the proposed modelling framework can be well adopted to analyse the continuous increase in stress and displacement during backfill operations.