The Influence of a Loose Layer Water Cut-off Curtain on the Slope Stability of Open-pit Coal Mines

Water-rich open-pit mines can have problems with large water inflows, slope reinforcement difficulties, and hazardous mining risks. The construction of a water cut-off curtain to control groundwater in the loose layer of an open-pit mine can effectively reduce the amount of water that must be pumped and eliminate the problem of flooding in the pit. However, the rise of the water level outside the curtain and changes in the geotechnical properties of the slope's material will affect the stability and safety of the pit's slope. A computational model was constructed and limit equilibrium and numerical simulation methods were used to determine the influence of a water cut-off curtain on the stability of the slope. Results show that with the the water cut-off curtain, the water level outside of the cut-off curtain in the loose layer of the open-pit mine continues to rise and the hydrostatic pressure and horizontal thrust of the slope body increases. As a result, the sliding force of the slope increases and the resisting force decreases, ultimately lessening the slope- stability coefficient (factor of safety) of the open pit. If the construction position of the curtain is moved outward, the stability coefficient of the slope will increase, assuming that the water level outside the curtain remains unchanged. Conversely, if the position of the curtain is moved toward the pit, the stability coefficient of the slope will decrease. The maximum shear stress on the slope increases as the water level outside the water curtain rises. The maximum shear stress is mainly concentrated at the toe of the slope of the first bench below the surface and at the interface between the curtain and the bottom of the loose material. If designed properly, the water curtain can control the water table in the slope's material, maintaining the stability of the slope.