Determine the Shear Strength Parameters of Mine Waste Dump Materials by Back-Analysis Method and Determine the Stable Height and Safe Distance of Waste Dump to the Wall (Case Study: Golgohar Mine No.1)

In orther to the stability analysis of Golgohar No.1 mine waste dump, cohesion and friction angle of materials is necessary to determine. Because the determination of these properties requires the use of in-situ shear test and large scale triaxial apparatus and expensive methods, hence, back-analysis method as a low-cost method can be used to determine the shear strength properties. Due to the tensile cracks are observed on the surface of the waste dump, so it can be considered safety factor approximately equal to unit and using the back-analysis method the shear strength parameters can be estimated. In this paper, the analytical and numerical methods by FLAC/SLOPE and Slide software and charts provided by Hoek and Bray have been used to determine the shear strength parameters of materials and their results were compared with each other. This analysis shows cohesion and internal friction angle for materials using analytical and numerical methods and Hoek-Bray charts obtained respectively 19.2 kPa ,24° and 21.4 kPa, 24° and 21 kPa, 24°. With the development of open pit mine and more mineral extraction, the amount of waste collected in the same proportion will increase. This increase is caused larger waste dump, that will threaten its stability on the one hand and the other hand because of the proximity to the mine walls can affect the stability of the wall. So with according to continuation of the waste dumping and transport costs, slope stability and height stable and optimal distance from the south wall of the mine must be considered. In this study, using numerical methods in order to achieve stable safety factor of 1.2 for the waste dump with change the height and angle of slope of the bench, the stable height and angle of slope has been obtained. Also, in order to determine the safe and optimal distance of waste dump from the wall of the mine the analytical methods used and the effect of distance on the safety factor of wall is investigated. The results show that at distances of less than 150 meters from the wall, the safety factor of wall is more reduced and this distance can be considered as a safe distance.