Numerical investigation of the stress distribution in backfilled stopes considering creep behaviour of rock mass

New paper published on Rock Mechanics and Rock Engineering

Paper Title: Numerical investigation of the stress distribution in backfilled stopes considering creep behaviour of rock mass

Authors: Chongchong Qi* & Andy Fourie

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 time-dependent behaviour of the rock mass (TDBRM). In this paper, a generic study was presented to investigate the effect of the TDBRM on the stress distribution in the backfilled stope using numerical modelling. The time-dependent characteristics of backfill stiffness and cohesion were also considered. A reference case was studied in detail followed by an extensive parametric study. The results show 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’ 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 proposed method can provide important guidance to underground mines during stope design for more efficient backfill operation and safer long-term stope stability.

Keywords: Stress distribution; Backfilled stopes; Time-dependent; Numerical modelling

Reviewer 1: This paper presents a series of 2D plane-strain numerical simulations using commercial software of FLAC-2D to study the stress distribution in a backfilled stope.  Frankly speaking, this topic is interesting to the readers. As a numerical practice, it looks successful. However the original contribution of the authors for the numerical model is not clear. In addition, there is no comparison of the numerical results with the field data. It is difficult to judge the numerical results are reliable or not. The detailed comments are as follows.

Representative figure from this paper:

Figure 7.jpg

Time dependent response in the reference case: a) displacement versus time, and b) stress versus time.

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