Undercutless caving at Newcrest: towards the next generation of cave mining

Abstract

Mass mining and particularly the cave mining industry is facing technical challenges that include those associated with greater depths, lower grades and demand for increased productivity (Flores 2014). New orebodies and expansion of current mines demand safer, faster, and lower-cost approaches to establishment and operation. The rate at which a cave is established is crucially dependent on the efficiency of the undercut process, which is becoming increasingly difficult and costly to execute in deeper orebodies. For these reasons, the development of alternative and more effective cave establishment methodologies has become critical. In this context, Newcrest has initiated the NextGen Caving programme, which endeavours to develop and implement novel, cost effective techniques for mining the next generation of block caves aiming to unlock low grade massive ore bodies at greater depths. Among the NextGen initiatives is the Undercutless Caving concept or Single Pass Cave Establishment (SPCE). This aims to improve safety, and reduce cave establishment time and cost, by establishing the drawbell and undercut components of a traditional block cave method from a single level and process. If proven to be successful, Single Pass Cave Establishment will not only change how Newcrest evaluates and constructs block cave projects, it will also represent a step change for the caving industry. To engineer, test, validate and implement this concept, Newcrest has embarked on an ambitious project consisting of a design study and two trials. This paper introduces the Undercutless Caving concept alongside the results of the first practical trial at the Telfer Mine in Western Australia. Successful results from a practical trial at Telfer have been achieved, with complete undercut and connectivity gained across the major and minor apex pillars of the planned four drawbell layout, of comparable pillar sizes to that at Cadia East. As an industry first of achieving drawbell and undercut establishment from a single level with no void above and with unprecedented drawbell and pillar dimensions, this milestone represents a significant step forward in cave establishment for the industry.

A Methodology to Determine Undercutting Height in Block/Panel Caving

“…This methodology has even been applied below the production level [11]. Alternatively, at the Newcrest mine, undercutting has been carried out from the production level to reduce costs and timelines and enhance the safety of this stage at high depths [12]. Also, confined blasting over the undercutting was used to increase the initial productivity [13].…”

Development of an optimal draw control strategy for a sublevel caving operation at Malmberget mine

“…The mine objectives are quantified into measurable Key Performance Indicators (KPIs). A common KPI used for optimising draw control is Net Present Value (NPV) (Jamieson 2012; Campbell and Power 2016). A draw control strategy which maximises NPV was chosen by the Telfer mine and the Ernest Henry SLC operations (Jamieson 2012; Campbell and Power 2016).…”

“…A common KPI used for optimising draw control is Net Present Value (NPV) (Jamieson 2012; Campbell and Power 2016). A draw control strategy which maximises NPV was chosen by the Telfer mine and the Ernest Henry SLC operations (Jamieson 2012; Campbell and Power 2016). Using NPV is popular for several different mining methods, as it is able to quantify all cost and revenue components over a period of time.…”

“…Hence, daily control of the loading operation at the draw point is required to determine when loading of a given ring should be stopped. Caving operations which do not measure ore grade at the draw point are unable to register this variation and must, therefore, use a uniform and static control of loading at the draw point (Jamieson 2012; Campbell and Power 2016; Shekhar, Gustafson, Schunnesson, et al 2016). The final extraction ratio targets are lower near the hanging wall, and the target increases as the draw point location moves from hanging wall to footwall (Campbell and Power 2016).…”