Calibration of Numerical Model Applied to a Shear Zone Located on a Slope in an Open Pit Mine—Case History

Evandro Moraes Da Gama,Bruno C R Da Silva

doi:10.4236/gm.2012.21002

Abstract

The instability of a pit mine slope diagnostic caused by the slipping of a localized deep shear zone is described. The slope was designed on ultra basic, serpentine and metabasite rock formations with an angle varying from 40 to 45 de- grees. The perturbed slope zone was classified as RMR 12 and the non-perturbed zone as RMR 75. The boundary of these zones is defined as the shear zone. The pit slope was field mapped in detail and the mechanical properties of the rock were obtained through a laboratory test. The lab data were further processed using the RMR mechanical classifi- cation system. The Distinct Elements Code numerical modeling and simulation software was used to design the pit slope. The model was calibrated through topographic mapping of the points on the ground. The task of calibrating a numerical model is far from simple. Exhaustive attempts to find points of reference are required. The mechanical be- havior in function of the time factor is a problem that has yet to be solved. The instant deformation generated in the numerical model generated functions that can be compared with the deformations of quick shifts acquired in the topog- raphic monitoring. SMR is indeed more often recommended for Pit Slopes, though the fact that we have used RMR does not invalidate the classification for the modeling effect. The main parameters such as spacing, filling, diving direc- tion and continuity allow for compartmentalization of the modeled area. The objective of the modeling was not to pro- ject slopes because this massif was undergoing a progressive slow rupture. The objective of the modeling was to study the movement of the mass of rock and its progressive rupture caused by a shear zone.

Highlights

The term shear zone [SZ] generally refers to an area close to where parallel boundary shear deformations are located
The instant deformation generated in the numerical model generated functions that can be compared with the deformations of quick shifts acquired in the topographic monitoring
This paper describes a diagnosis of the destabilization of a slope located on the eastern side of an open pit caused by the slow slide into depth of a shear zone, identified as a member of group 1

Summary

Introduction

The term shear zone [SZ] generally refers to an area close to where parallel boundary shear deformations are located. The shear zones are formed by the relative movement of blocks of non-deformed, brittle rocks located on opposite sides moving in opposite directions. The shear zone moves on a parallel plane between the blocks as a result of the movement of the blocks towards both sides. This plane is called the shear plane. The main structures for the stability of slopes are foliations; brittle-ductile shear in fault zones. Ductile-brittle shear and fault zones appear in profusion in the open pit forming a cross network .The shear zones have variable extensions reaching up to several tens of meters. Many of them show evidence of having moved more than once

Results

Discussion

Conclusion