Rock mechanics

BGS undertakes both applied rock mechanics research and standard internationally recognised tests to investigate the mechanical and physical properties of near-surface rocks (less than 5km deep) and building stones. Tests are performed to the 'suggested' ISRM (2007) and ASTM (1995) standards where applicable. The facility performs a range of classification (index), strength and deformation tests on core samples with diameters of 38mm, 50mm & 100mm to ASTM (1995) standards. The primary focus of research is performing novel tests to obtain data that underpin the national datasets of the BGS on the geotechnical properties of UK rocks. Staff experience includes rock and soil mechanics, engineering geology, petroleum engineering, hydrogeology, biological sciences, and numerical modelling.

The testing facilities at BGS underwent a comprehensive upgrade in early 2011 with the introduction of an MTS triaxial rock deformation rig. This state of the art apparatus allows testing of rocks ranging from unconfined conditions, through to depths of 6 km, with temperature from room temperature to 200 degrees C. A range of testing scenarios can be simulated, including creep tests, uniaxial strength tests, constant strain rate tests and complex stress-paths.

Data from these studies are used in the development of robust models that describe the geotechnical properties of rocks and feed into the national databases on geotechnical properties of rocks.

Parameters

Apparatus and experimental systems are customised to meet specific requirements of a project. Experiments are performed under simulated down-hole stress, pore pressure and chemical conditions using uniaxial, triaxial, or shear apparatus. All of our facilities are carefully temperature controlled, with some apparatus in constant-temperature environmental chambers, so as to maintain constant temperature conditions. With careful attention to experimental design, choice of instrumentation, calibration and regulation of testing conditions, BGS is able to quantify key parameters including:

  • Index (density, effective porosity, and moisture content)
  • Uniaxial Strength
  • Uniaxial Deformation
  • Triaxial Strength
  • Triaxial Deformation
  • Rheological properties (creep parameters)
  • Indirect Compressive Strength
  • Direct Shear Strength (Portable rock shear box)
  • Indirect Tensile Strength (Brazilian disc method)
  • 3D Swelling Strain
  • Slake Durability
  • Point Load
  • Sonic Velocity (P & S wave)
  • Thermal properties
  • Intrinsic permeability

Rock samples are carefully prepared in order to maintain saturation, minimise damage and to be as close to in situ conditions as possible.

Applications

Our research outputs are used widely within the BGS and feed into many of the models produced by the BGS. Our customers are British, European and International Agencies, regulatory bodies, private-sector companies and consulatncies working in:

  • Engineering geology
  • Radioactive waste disposal
  • CO2 sequestration
  • Hydrocarbon prospecting

Examples of experimental studies include:

  • Building stones of the United Arab Emirates
  • Rock mechanics properties of the caprock material from the North Sea

Recent publications

Cuss, R.J. and Harrington, J.F. (2011) Update on dilatancy associated with onset of gas flow in Callovo-Oxfordian claystone; Progress report on test SPP_COx-2. British Geological Survey Commissioned Report, CR/11/110. 34pp.

Entwisle, D C. (2007) The Engineering Geology of the A74M and M6 in the Solway area. British Geological Survey Internal Report, IR/07/031. 27pp.

Hobbs, P. R. N and Freeborough, K.A. (2006) Triaxial strength tests on till samples from the Slope Dynamics Project – Happisburgh, Sidestrand, and Aldbrough. British Geological Survey Internal Report, IR/06/065. 17pp.

Horseman, S.T., Harrington, J.F., Birchall, D.J., Noy, D.J. and Cuss, R.J. (2005). Consolidation and rebound properties of Opalinus clay: A long-term, fully-drained test. Commissioned Report CR/05/128. British Geological Survey, Environmental Protection Programme.

Reeves, H.J., Cuss, R.J., and Evans, C.J. (2003) Critical stress analysis as a predictor of fluid flow; the answer or just another piece of the jigsaw? In: Fault and Top Seals : What do we know and where do we go? EAGE Confernece, Montpellier, France. 8 - 11 September 2003.

Hobbs, P.R.N. and Akhurst, M.C. (2002) Characteristic geotechnical properties of solid and drift geological units from site investigations, southern Central Belt of Scotland. British Geological Survey Internal Report, IR/02/184. 8pp.

Contact

Please contact Dr Helen Reeves for more information