Failure characteristics and mechanism of a landslide in weathered phyllite at Anqian iron mine, Liaoning, China

A landslide occurred on November 24, 2019, in weathered phyllite at the western longwall of Yabaling open pit of Anqian iron mine in Anshan City, Liaoning Province, China. The landslide was estimated to be 3.0 × 10 4 m 3 in volume and caused severe damage to the road of transporting waste materials. This landslide was a typical jointed rock mass landslide, and the cause of the landslide was related to four factors: open-pit mining activity, the weak rock, discontinuities, and the high rainfall. According to the failure characteristics, the landslide area was divided into three parts: the tension-cracking area, the sliding-deformation area, and the colluvium area. The failure mechanism of the landslide was investigated through a back analysis combining nonlinear Hoek–Brown criterion and FLAC3D program with a parameter reduction technique. The results showed that the predicted sliding surface at the critical state matched closely the field observations. A remedial scheme of landslide stabilization including four rows of micropiles was proposed and the stabilization mechanism of the micropiles was discussed. The shear strain increment contours show that the micropiles arrested the original sliding surface and controlled the movement of the sliding mass behind them, and thereby significantly improved the stability of the landslide. This paper also presents the results obtained from the parametric analysis in order to understand the impact of strength parameters on the long-term stability of the stabilized slope. The findings improved understanding of the failure characteristics and mechanism of jointed rock mass landslides may be used for evaluating the stability of slopes and early identification for both active and inactive open-pit mines.