Glencore Mining - North Queensland Australia

Sector: Mining

Procurement Type: Design Analysis

Owner: Glencore

NOMA´s client: Mount Isa Mines

Design Period: 2017

 

The Project

Mt Isa Mines’ is currently mining the N3500 Orebody in North Queensland. The underground mining method is described as top down long-hole stoping with cemented paste fill. The extraction sequence requires both horizontal (underhand) and vertical exposure of the paste filled stopes.

The aim of the project was to conduct a series of numerical analyses to determine the strength required to maintain stability of underhand paste fill exposures throughout the planned extraction sequence of the N3500 Orebody.

Key Aspects

Underhand paste fill exposures must be strong enough to prevent failure of the entire fill mass and major sloughing of the vertical and underhand exposure faces.  Paste fill exposure stability is a function of the following:

• exposure geometry,
• stope extraction and filling sequence,
• hangingwall – footwall closure,
• surrounding rock mass failure,
• initial stresses within the fill mass,
• internal cold joints or segregation within the fill mass,
• dimensions of the fill mass, and
• shear strength of the fill.

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To analyse the performance of paste exposures, a rigorous three-dimensional numerical modelling approach is required.

Scope of Works

NOMA Consulting was engaged by Mount Isa Mines to conduct the following:

• Construct a three-dimensional model to simulate the historical extraction and filling sequence within the N3500 orebody. It is important to accurately simulate the filling and hydration sequence of each stope to provide a rigorous assessment of the internal stress distribution (arching) within each fill mass.
• Calibrate the previous vertical paste fill exposure performance using available geomechanical and monitoring data.
• Assess the stability of planned underhand paste fill exposures