Underground Mine Geotechnics

The derivation of geotechnical mine design criteria is a fundamental aspect of the development and operation of underground mining projects. The successful development and operation of an underground mine requires the design and installation underground support systems appropriate to the rock conditions and the excavation geometries. This allows ore extraction to be maximised and reduces waste dilution. Support of large capital development excavations is required so that these facilities operate for their design life and support of temporary extractive and haulage development can be required in areas of high mining induced stresses.

Approach

An appropriate mining method is selected based on the orebody geometry and the rock mass characterisation of the orebody, footwall and hangingwall rock masses. For the selected mining method, detailed mine design parameters such as excavation spans, and pillar size, stope support, excavation sequencing together with caveability, fragmentation and dilution estimates are developed using a variety of empirical and analytical techniques, including:

  • A thorough assessment of geotechnical conditions in the vicinity of the excavation to be supported by geotechnical mapping of adjacent underground development or geotechnical logging of exploration or geotechnical borehole core.
  • Rock mass classification studies would be carried out using Barton's Q system, Bieniawski's RMR system or Laubscher's mining rock mass rating system as appropriate.
  • Rock loading and potential instability mechanisms would be determined from rock block kinematic evaluations, from numerical stress analyses, and from dynamic considerations.
  • Rock/support interaction, including both rock reinforcement and concrete/shotcrete linings, would be analysed using numerical stress analysis techniques.

Deliverables

  • Definition of the expected ground and stress conditions and regional and local support types.
  • Specification of the most appropriate support which will maintain stability for the expected life of the underground opening under all anticipated loading conditions.
  • Improved underground safety, and elimination of extra support work, resulting in reduced costs.
  • Underground monitoring systems e.g. Cave monitoring, stress monitors, closure meters, seismic monitoring.
  • Fragmentation prediction.

Experience

SRK has world class expertise in geotechnical data gathering and the evaluation of a wide range of mineral deposits. Its engineers are recognised experts in rock mass classification. They are skilled in the interpretation of geotechnical conditions, in the evaluation of potential rock loading, and in the analysis of underground excavation stability.

SRK’s expertise is backed up by significant worldwide project and operational experience in the whole range of mining environments.

Services

  • Design and management of geotechnical investigation, drilling and laboratory testing programmes.
  • Core logging, geological and geotechnical mapping and rock mass characterisation
  • Structural interpretation and analysis.
  • Mining method selection and mine excavation sequencing.
  • Underground excavation stability analysis and stress modelling.
  • Development of geotechnical mine design criteria and underground support design.
  • Development of underground monitoring systems.
SRK Sweden