Abstract: Tunnel leakage happens very often through shield tunnel joints and grouting holes. It can induce the pore pressure decrease around the tunnel and then result in tunnel and ground settlements. In tunnel engineering, Grouting is usually used to prevent tunnel leakage. What’s more, the synchronous grouting is considered to be the first barrier of tunnel leakage. To investigate the effect of grouting on tunnel leakage, the permeability of inert and cement grouting is firstly studied using laboratory tests. The experimental results show that the permeability of both inert and cement grouting decreases with time and consolidation pressure at the early ages of grouting. The stable permeability of inert grouting is higher than that of the cement grouting. Thus, the cement grouting rather than the inert grouting can be used to prevent tunnel leakage. Then, the predicting method of tunnel leakage-induced pore pressure decrease is suggested considering the effect of grouting and tunnel lining. The calculations results show that the cement grouting can reduce the tunnel leakage-induced pore pressure decrease. Furthermore, the effect of grouting on tunnel leakage-induced pore pressure change depends on the permeability of tunnel lining. Finally, a dimensionless parameter RP is proposed to describe the relationship of tunnel leakage-induced pore pressure change and the permeability of grouting and tunnel lining. The results show that the grouting can reduce the decrease of leakage-induced water pressure, while, the effect of grouting on tunnel leakage depends on the relative permeability of tunnel lining and surrounding soils.

Key words: grouting, shield tunnel, leakage, pore pressure, relative permeability