Abstract: In deep excavations and large open pit mines, due to the spatial variation of geo-material properties, eva‎luating the stability of slops is often a challenging task. Several methods of slope stability analysis based on a wide range of assumptions and approaches have been implemented in commercial software packages to facilitate the process of stability analysis in inhomogeneous and multilayered slopes. However, choosing an appropriate method is very important because using an unrealistic or inappropriate method may lead to catastrophic consequences in terms of life and finances. In addition, the shear strength of geo-materials, analysis methods, and time-dependent rock deformations which is called creep can also significantly affect the result of slope stability analysis. In this study, a sensitivity analysis carried out on the K0, internal friction angle, Poisson’s ratio, modulus of elastic, time-dependent rock characteristics and cohesion and their effects on the Chadourmalu slopes stability are analyzed applying 3D numerical simulation. Chadourmalu open pit mine is the largest producer of iron ore in the northeast of Yazd. With more than 30 years of operation and reaching a depth of 225 meters, this mine is nearing the end of its working life, and now this open pit mine inevitably faces the complexity of long-term (time-dependent) stability conditions. Creep is a continuous, time-dependent deformation while the stress level is constant. According to the evidence of long-term instability potential, the displacement variations of the northern walls to the east of the pit have been investigated in the period of 18 months since December 2017. According to the long-term displacements measured in the mine wall using radar and back analysis performed using numerical simulation, a three-dimensional model was made using FLAC3D software, and the parameters of the Maxwell model, which includes shear modulus and viscosity, were eva‎luated. The viscosity value obtained from model calibration is 7e10 MPa days. After the numerical model calibration, the effect of three scenarios on the stability of the mine wall has been investigated. In the first scenario, the effect of time, in the second scenario, the effect of bench removing in the first eight bench and in the third scenario, the effect of increasing the depth on the displacements and stability of the slope was investigated. To consider the uncertainty related to the ratio of horizontal to vertical stress, three value is considered for K0 which are 0.5, 1 and 1.5 and their effects on the slope stability and displacements magnitude are analyzed applying numerical simulation. Based on the numerical simulation results, the horizontal to vertical stress ratio of 1.5 matches the measured displacements and the evidence of unstable zones in the mine wall. In the first scenario, in the three selected K0 values (0.5, 1, and 1.5), after 15 days, the uplifts have increased by 169%, 127%, and 123%, respectively, and the subsidence has increased by 88%, 128%, 244% percent, respectively. Increasing the width of first and second benches reduces the instability potential, and increasing the width of third to eighth benches increases the instability potential due to the weight reduction in the slide heel. The increase in pit depth in the third scenario leads to developing another sliding zone around 10th to 17th benches.

امين ازهري

امين ازهري , عليرضا ياراحمدي