Discrete element modeling of strata and surface movement induced by mining under open-pit final slope

• An EJRM method is proposed to model strata movement caused by mining under pit slope.
• The EJRM is able to model the caving and large displacement movements of rock masses.
• Parameters of the EJRM are determined using measured data and back analysis method.
• The monitored slope failure compared very well with the numerical results.
• Mining under the final slope of an open-pit was simulated using the proposed method.

Ore mining under the open-pit final slope will result in caving and large displacement movement of rock-masses surrounding the goaf. It is difficult for numerical methods that equate jointed rock-masses to a continuum to simulate the aforementioned mechanical behavior of rock-masses. However, the placing of joints in a calculation model according to their actual distribution characteristics will result in an excess of model blocks, which renders the calculation impossible. To solve this problem, a numerical modeling method based on an Equivalent Jointed Rock-mass Model (EJRM) is proposed in this paper. First, the rock-masses in the research area are simplified as an EJRM; then, a back analysis method, combining orthogonal design and numerical simulation with Discrete Element Method (DEM), is used to invert the mechanical parameters of the model; lastly, the DEM is utilized to analyze the movement and failure of the strata and surface induced by mining under open-pit slope. The Yanqianshan iron ore mine was treated as an example in the present study. Mining under the eastern slope of the open pit of the mine was simulated by means of the aforementioned method. The patterns of the failure and movement of the strata and slope at different mining stages were obtained. This numerical modeling method proposed can be used to simulate complex mechanical behaviors of rock-masses induced by underground mining.