Blasting near open pit walls

Abstract

The topic of blasting near pit walls is one that invokes mixed reactions from different mining departments. For many mine operations and mine scheduling departments, it often represents a significant disruption to efficient work flow, while to geotechnical departments it represents a critical component in the task of delivering safe and competent pit walls and compliance with pit slope design. Many different approaches exist to help achieve the desired end result of safe pit walls and compliance with pit slope design, suggesting that there is no single best-solution. This paper explores some of the contemporary paradigms which strive to achieve the desired end result, with a particular focus on presenting a thought process aimed at trying to avoid unnecessary and ineffective restrictions on mining practices and wall control blasting. Practices such as reduced blasthole diameter, pre-splitting, trim blasting, initiation sequences and systems and reduced blast size will be explored using modelling based upon field measurements. How well do we understand the impacts of blasting on pit wall integrity and pit slope stability? While there is no single design that suits all mining applications, there is a single thought process that should lead each mine to quite quickly decide on the most appropriate solutions for areas of different sensitivity regarding slope stability.

Correlating blast vibrations and geomechanical properties to determine damage profiles and improve wall conditions in open pit mining

“…Thus, the ratio of bench height and damage extension is 1.1, the smallest value simulated. The results in Table II show that adequate timing and sequencing and the use of buffer rows promote a strong impact on damage, corroborating the results stated by McKenzie (2016).…”

“…In addition, it correlates this damage to the bench height, according to parameters used in blast design such as buffer rows and confinement. McKenzie (2016) points out the three main mechanisms of damage caused by blasting: induced vibrations (responsible for creating new fractures), extreme gas pressure (responsible for the expansion of fractures) and release of load (responsible for the creation of fractures parallel to the rock movement). Those are very important factors while addressing pit slope stability.…”