Abstract
Tunneling in weakness zones containing swelling clay represents one of the most difficult conditions in hard rock tunneling. Evaluation of rock support requirements in such zones is normally empirical, i.e. mainly based on experience. In this paper, rock supports in a major weakness zone containing swelling clay is analysed based on monitoring results and numerical analysis in order to enrich the experience of support evaluation under such conditions. The Finnfast subsea road tunnel is used as a case. Laboratory tests of the gouge material from the actual zone indicate that the swelling pressure is moderate. All instrumentation data and simulation results show that the loading on the sprayed concrete is far less
than its compressive strength, even for the rock support without the reinforced sprayed concrete rib. This suggests that such zones may often be excessively supported when the swelling clay is not very active. It is also found that for reliable stability control through such zones the instrumentation should be installed as close to the excavation face as possible.
than its compressive strength, even for the rock support without the reinforced sprayed concrete rib. This suggests that such zones may often be excessively supported when the swelling clay is not very active. It is also found that for reliable stability control through such zones the instrumentation should be installed as close to the excavation face as possible.