Kink Effect on the Stress Distribution in 2D Backfilled Stopes

Mining backfill is increasingly used in underground mine stopes around the world. A good understanding of the stress distribution in backfilled stopes is a critical concern for the design of barricades, sill mats and side-exposed backfills. In this regard, several published numerical studies reported that the vertical stress versus depth curve can exhibit an increased pace with depth near stope bottom. This phenomenon, known as kink effect, can significantly affect the stress estimation for the design of barricades and base-exposed backfill. In addition, the mechanism of kink effect has never been fully investigated, nor considered in analytical solutions developed for evaluating the stresses in backfilled stopes. In this paper, the mechanism of kink effect is first analyzed and then taken into account in an analytical solution. It is found that the occurrence of kink effect mainly depends on yield or unyield state of backfill, which is in turn determined by the Poisson’s ratio μ and internal friction angle φ of the backfill. A conceptual analytical solution is then proposed to evaluate the stress distribution in 2D backfilled stopes by considering the kink effect near the bottom. The proposed solution was first calibrated by a few numerical simulations performed with FLAC2D. The results showed that kink effect takes place, starting from the bottom of stope along a height equaling to 10th and 20th of the backfill’s total thickness for the vertical and horizontal stresses, respectively. The calibrated analytical solution was further validated by additional numerical simulations with different backfill properties.