SRK has provided rock mechanics services to the Chirano Mining Operation over a number of years and has undertaken rock mass characterisation, geotechnical analysis and design studies at the majority of its deposits in support of mine life extension projects. Each deposit started life as an open pit mine but has since transitioned to underground. SRK’s work for Chirano has focussed on underground mine rock mechanics and underground/open pit interaction.
For the Paboase Mine, SRK prepared geotechnical guidance and undertook a fatal flaw assessment for a longitudinal modified sub-level cave (SLC) mining method using a combination of elastic MAP3D modelling, RS2 modelling and empirical assessment. As production using this mining method was implemented and the resource extended with depth, we developed an inelastic FLAC3D model calibrated against cavity monitoring survey (CMS) data which we updated on an annual basis to simulate the response of the rock mass to mining. This model was used to assist with the provision of geotechnical guidance as SLC mining progressed to deeper levels and carry out an assessment of the impact of underground mining on crown pillar stability and surface infrastructure, ventilation fan, portal accesses and open pit sumps.
For the Akwaaba Mine, which also utilises a longitudinal modified SLC mining method, SRK undertook MAP3D elastic modelling to develop geotechnical strategies for extending the existing underground mine down dip and along strike as well as assessing the geotechnical viability of extracting orebody splays extending into the hangingwall of the main orebody. The modelling was used to guide mining sequence, identify stress concentrations in pillars and access development and determine stope stability and optimum stope dimensions.
For the Akoti Mine, which utilises a long hole open stoping mining method with waste rock backfill, FLAC3D modelling and empirical pillar assessments (Lunder and Pakalnis) were used to optimise stable stope and pillar dimensions for current and future mining scenarios, down dip and along strike orebody extensions. Crown pillar stability and sizing was also determined along with the impact of crown pillar extraction on the stability of open pit walls.
SRK has also carried out geotechnical characterisation and analysis of the Suraw, Tano and Obra deposits. These deposits were originally mined by open pit. Exploration drilling has identified potential underground extensions of the orebody below the open pit. Feasibility level underground geotechnical design guidance has been prepared for these deposits to support the development of underground mine designs. RS2 numerical modelling along with empirical analyses were used to estimate stable stope, rib and sill pillar sizes, geotechnical dilution, crown pillar sizing along with ground support requirements for capital and extractive development.
