Abstract:

Based on the distribution and occurrence characteristics of underground shallow gas in Hangzhou area, and combined with the Hangzhou Metro project, a model test system was established; and influences of gas release and re-accumulation of the shallow gassy soil on stabilities of metro tunnel were studied by the physical model test. Results show that gas actions of shallow gassy soil may cause the tunnel crossing gas reservoirs to generate additional deformations and internal forces; disturbances on relative deformation and internal force of the shield lining segments are little; but influences on the global deformation of tunnel structures are significant; values of the additional deformation and internal force caused in gas re-accumulation are much less than those in the former process of gas release. For the metro tunnel in regions buried shallow gas, global stability of tunnel structure should be as the control emphasis; and the gas in strata should be released under control before construction so as to reduce the later adverse effects on metro engineering.

Key words: shallow gas, gassy sand, metro tunnel, stability, geological disaster