Abstract

The accuracy of the basic input data is extremely important in slopes stability analysis. Primarily such inputs include orientation of the planes of weakness (joints) existing in the rock mass in question, as well as parameters of the shear strength along these joints and across the rock mass. More accurate knowledge of the inputs permits reliability of the analyses to be enhanced and excessive safety margins to be avoided. The task of this study was to assess the impact of the key input parameters on slope stability of the open pit mine inYakutia. A parametric analysis of such input data such as: dip angles of flat and steep fractures, their parameters of shear strength (tan φ and C) and of the rock mass, rock density, and angle of inclination of the open pit mine slope was performed.

Introduction

Effectiveness of an open cut mining as well as creation of high engineered slopes and rock excavations depend on correct determination of the general angle of slope inclination. The accuracy of the main input data is extremely important in stability analysis. Assuming that the safety factor of a rock mass k is the product of combination of the basic design parameters pi such as:

  • – dip angles of potential sliding surfaces,

  • – parameters of shear strength along these surfaces,

  • – rock density,

  • – dip angles of the slope,

  • – method of stability analysis applied,

it is possible to assess the effect of potential influence of each parameter by a value of the safety factor ∂ k/∂ ?i: k =f (?i) (i=1, 2, …) using the parametric analysis method (Londe 1984, 1988, Gaziev & Rechitski 1985). This method permits to define the most sensitive parameters, and efforts should be concentrated on their more precise specification.

2 Open Pit Mine and its Geological Structure

The task of this study was to assess the impact of the key input parameters on stability of the open pit mine slope of one of the deposits inYakutia. The main host rock is sandstone of variable preservation. The designed depth of the open cut works out to be 300m (Fig. 1).

The southern slope of the open cut with three joint sets dipping towards the cut facewas investigated: joint set I dip at 30°–60°, joint set IV dip at 70°–90°, and joint set V dip at 50°–60°. The results of geological mapping of the rock mass show that the joint of sets IV and V occur more frequently in the rock mass are longer than the joints of set I, and therefore potential failure of the rock mass in the form of rotational block slide was also considered in the analysis.

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