The construction of large-span caverns in hard rock in a major underground storage project is discussed in this paper. In-situ stresses were measured using hydraulic fracturing and 3-D over coring during construction, showing a horizontal stress ratio of 2-3 times the vertical stress. Rock reinforcement design was based on the Q-system combined with numerical modelling for special design cases. Tunnel performance were checked and monitored by in-situ instrumentation, including deformation, convergence, and bolt load. A measuring borehole was drilled into the virgin rock before rock excavation, which provided a direct and very insightful comparison with various deformation measurements made during rock excavation. It has proven that the high horizontal stresses are very favourable to stability of the opening.
|Journal||International Journal of Rock Mechanics and Mining Sciences|
|Issue number||SUPPL. 1|
|Publication status||Published - 1 May 2004|
- Horizontal stress
- Large-span tunnel
- Site monitoring