Numerical assessment of failure potential of a large mine waste dump in Panzhihua City, China

Catastrophic landslides occur frequently at large waste dumps, causing huge losses of lives and environmental degradation. In this study, Zhujiabaobao iron mine waste dump was surveyed and found to be unstable during a field investigation in April 2016. A failure potential assessment was undertaken for the waste dump; this is crucial for the prediction and mitigation of landslides hazards. Reconnaissance, geomorphological analysis, and laboratory experiments were carried out to provide basic data, and a three-dimensional waste dump model was constructed. To consider ground cracks in the waste dump and acquire information about potential sliding mass, an extended finite element model (XFEM) based on strength reduction technique was applied. An analysis shows that the factor of safety (FOS) of waste dump is 1.22, not very stable according to The technical code for building slope engineering (GB50330-2013) published by Chinese ministry of Housing and Urban-Rural Development, and the potential failure volume is 45 x 10(4) m(3). Then, the potential landslide and debris flow due to slope failure were simulated using the software SFLOW based on a free-surface shallow water model (SWM). The landslide simulation considers different water contents of sliding mass, reflected in parameter C-v (sediment concentration by volume), whereas debris flow simulation was designed for 20, 50, 100, and 200-year return periods. The results show that with the decrease in C-v, the speed of sliding mass increases, and the run-out distance of landslide increases. However, even the farthest influence distance does not reach downstream buildings. The debris flow can pile up in front of gully mouth and even run into the Jinsha River. Therefore, once a landslide has occurred or when a lot of loose material is present, corresponding management measures (such as cleaning the material or setting the retaining wall) and a forewarning system should be developed to prevent huge damage caused by debris flow.