Deterioration and instability mechanisms of water-rich and weakly cemented open-pit slopes

Authors

WANG Ming, Zhaluteqi Zhahanao’er Coal Industry Co., Ltd., Zhaluteqi 029100, ChinaFollow
WU Zhang, CCTEG Xi’an Research Institute (Group) Co., Ltd., Xi’an 710077, China; National Coal Industry Key Laboratory Engineering Geological Laboratory, Xi’an 710077, ChinaFollow
XU Changyou, State Power Investment Corporation Inner Mongolia Energy Co., Ltd., Tongliao 028000, China
ZHAO Fu, CCTEG Xi’an Research Institute (Group) Co., Ltd., Xi’an 710077, China; National Coal Industry Key Laboratory Engineering Geological Laboratory, Xi’an 710077, China
MENG Xiangchun, State Power Investment Corporation Inner Mongolia Energy Co., Ltd., Tongliao 028000, China
SHI Bin, CCTEG Xi’an Research Institute (Group) Co., Ltd., Xi’an 710077, China; National Coal Industry Key Laboratory Engineering Geological Laboratory, Xi’an 710077, ChinaFollow
LIU Jingyu, Zhaluteqi Zhahanao’er Coal Industry Co., Ltd., Zhaluteqi 029100, China
XU Yongchao, Zhaluteqi Zhahanao’er Coal Industry Co., Ltd., Zhaluteqi 029100, China
WANG Jingwei, Zhaluteqi Zhahanao’er Coal Industry Co., Ltd., Zhaluteqi 029100, China
ZHAO Lichun, Zhaluteqi Zhahanao’er Coal Industry Co., Ltd., Zhaluteqi 029100, China

Abstract

Background During the mining of an open-pit mine, denudated layers contain loose Neogene and Quaternary aeolian, alluvial, and diluvial deposits, facilitating water storage and conduction. This is prone to cause slope degradation and instability, severely threatening mining safety. Methods Based on results from field surveys and laboratory experiments, this study systematically analyzed the impacts of groundwater on the weak layer along a slope of an open-pit mine in the Huolinhe Coalfield, Inner Mongolia, focusing on its softening effect on mudstones. By establishing a mechanical model for unconsolidated strata, this study derived an equation for calculating the seepage force in the accumulation layer and quantified the impacts of groundwater level on the factor of safety (FoS) of the slope. The findings were validated through numerical simulation, thereby revealing the mechanisms behind the slope degradation and instability caused by groundwater. Results and Conclusions The results indicate the basal mudstone layer of the slope is severely weathered, with joints well developed. This layer, together with the Quaternary sandy soil layer, forms the weak layer of the slope. The mudstone layer is low-lying due to the structural influence and is impermeable, rendering its overburden rich in water in the long term. Influenced by groundwater, the weakly cemented accumulation layer is prone to deformations and failure under the action of the seepage force, while the mechanical properties will be reduced by groundwater. Therefore, the slope’s topography facilitates water convergence, and the presence of the weak layer represents a major cause of the slope instability. Furthermore, the slope instability is exacerbated by the groundwater-induced seepage force, buoyancy, and rock-soil mass degradation. Accordingly, it is advisable to intensify systematic hydrogeology research and take the prevention and control measures including the interception of external water and drainage of internal water.

Keywords

open-pit slope, weak cementation, water-rich, numerical simulation, instability mechanism, prevention and control measures

DOI

10.12363/issn.1001-1986.25.03.0192

Recommended Citation

WANG Ming, WU Zhang, XU Changyou, et al. (2025) "Deterioration and instability mechanisms of water-rich and weakly cemented open-pit slopes," Coal Geology & Exploration: Vol. 53: Iss. 8, Article 14.
DOI: 10.12363/issn.1001-1986.25.03.0192
Available at: https://cge.researchcommons.org/journal/vol53/iss8/14

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