The selection of mining methods for any resource needs to be addressed from a geotechnical viewpoint. For an open pit operation, slope stability will be paramount in determining stripping ratios and hence overall mining costs. AMC staff will review existing data including previous site investigation programmes and mapping exercises conducted at the mine site. In conjunction with detailed mapping and logging of core, this will help to define the ground water regime, major discontinuity sets and intact rock material properties so that pit slope design can be optimised. Laboratory testing of rock and soil samples can be carried out if required.
For an existing or proposed underground mine the geotechnical engineering and ground control studies focus on slightly different aspects. Review and analysis of existing data and detailed scan line and borehole logging will contribute to an assessment of expected mining conditions and ground control problems for the mining operation. The rock mass characterisation process can include:
- Geotechnical data collection programmes from borehole information and underground or surface exposures
- Virgin in-situ stress measurement and pillar stress measurement
- Design and installation of underground monitoring systems and assessment of results
- Likelihood of caving and associated surface subsidence
- Assessment of the interaction between surface and underground mining operations
- Investigation of hydrogeology, ground water inflow and drainage rates
- The need for and role of backfill in the mining operation
- Design of mining spans, pillars and extraction sequences using empirical and numerical techniques
- Design and support recommendations for the long term stability of permanent underground facilities such as shafts, crusher stations, pump chambers and workshops
- Rock breakage and specific blast design requirements
Many of the inputs to mine design and mine planning will come from this rock mass characterisation phase. Solutions to most of the problems encountered during the feasibility study will come from AMC's blend of experience and detailed understanding of the relevant technical factors that are involved. Depending on the nature and complexity of these technical factors, study programmes ranging from 2 and 3 dimensional computer simulations to in-situ testing and monitoring can be designed and conducted.
