Stress Field Assessment For Determining The Long-Term Rheology Of A Granite Rock Mass
2016 (English)Conference paper (Refereed)
A case study is presented to show how stress field information can be used to assess the long-term rheological behaviour of an equivalent geo-material. The example concerns a granitic rock mass at the km3 scale where an underground hydropower scheme including a new 10 km long power conduit and a powerhouse complex located about halfway in the conduit and 500 m below ground level will be constructed. For design of the underground cavern and hydraulic pressure tunnel, several in situ stress measurements were carried out, using hydraulic, overcoring and flat jack techniques. Integration of the several in situ test results through a continuum mechanics model shows that the long-term behavior of this granite rock mass differs markedly from the short-term behaviour as defined by laboratory measurements on cores. The large scale stress field is found to depend mostly on the softer material that fills up the faults and hence results from the shear stress relaxation over a large number of pre-existing fractures and faults. The overall granite rock mass may be viewed as a combination of stiff elastic blocks separated by soft low strength material, leading to a fairly large scale homogeneous axisymmetrical stress field with vertical axis, with local strong anomalies that correspond to either high or low stress magnitudes.
Place, publisher, year, edition, pages
In situ stress measurements, regional stress field, elastic rock mass, shear stress relaxation, natural fracture network
Earth and Related Environmental Sciences
IdentifiersURN: urn:nbn:se:uu:diva-293981OAI: oai:DiVA.org:uu-293981DiVA: diva2:928463
7th International Symposium on In-Situ Rock Stress RS2016, Tampere, Finland