The influence of loose layer water cut-off curtain on the slope stability of open-pit coal mines

Abstract Water-rich open-pit mines in China face the problems of large water inflow, slope reinforcement difficulties and high mining risks. The construction of a water cut-off curtain to control groundwater in the loose layer of open-pit mines can effectively reduce the amount of water drainage, thus solving the problem of flooding in open-pit mines. However, the rise of the water level outside the curtain and the change in the geotechnical properties of the slope will affect the stability and safety of the slope of the open-pit mine. A computational model was constructed, and the limit equilibrium method and numerical simulation method were used for calculation and analysis to study and analyse the influence law of the water cut-off curtain of the loose layer on the stability of the slope. The research results show that under the effect of the water cut-off curtain, the water level on the 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 increase. As a result, the sliding force of the slope increases and the anti-skid force decreases, ultimately leading to a decrease in the slope stability coefficient of the open-pit. Assuming that the water level outside the curtain remains unchanged, if the construction position of the curtain is moved outwards, the stability coefficient of the slope will increase; conversely, if the position of the curtain is moved inwards, 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 platform below the surface and at the interface between the curtain and the bottom of the Quaternary System. The water curtain can control the water table. The water cut-off curtain can control the groundwater level of the slope and maintain slope stability.