Ground Response to the Construction of Shanghai Metro Tunnel-Line 2

Numerical prediction of long-term settlements over tunnels in clay

“…Similar widening has been reported by a number of authors (Glossop, 1982;Shirlaw, 1995). The increase of long-term settlement reached 60-90% of the total settlement for No.2 metro tunnel in Shanghai, meanwhile the width of the settlement rose from 2.645a in the first month to 2.742a (a is the radius of tunnel) in the third month after construction (Lee et al 1998, shown in Figure 1b). The long-term settlement can affect the function of the tunnel and the safety of the surroundings.…”

Numerical Study on the Effect of Grouting on Long-Term Settlement of Tunnels in Clay

“…However, [4] pointed out that the effects of grouting around tunnel linings deserves more attention than it has generally been given and its influence on settlement must be taken into account when the detailed long-term behaviour of tunnel is studied numerically. The field-based measurement from Shanghai metro tunnel line-2 also confirms that the effect of grouting on the excess pore pressure is quite remarkable and not reasonable for neglecting ( [2]). [9] studied the effectiveness of grouting on tunnels in clay during long-term through field trial, laboratory test combined with numerical simulations.…”

“…The shield body is 6.24m long with 6.34m in diameter. Correspondingly, the clearance between the external diameters of shield body and the tunnel, which is usually named physical gap p G according to the definition of [2], will reach 140mm. Correspondingly, the FEM mesh of the tunnel is shown in Fig.1 combined with soils distribution.…”

“…[7] reported that this kind of long-term settlement might last two or more years in saturated soft ground even without any surface loading for Shanghai urban subway tunnel. The surface settlement of Shanghai metro tunnel line 2 almost doubled in three months after the tunnel construction ( [2]). Based on comprehensive field data, [4] concluded that typically the increase in settlements over long-term is of the order of 30%-90% of the total settlement.…”

“…Many field observations on long-term settlements of tunnels have indicated that the long-term settlements can be significant when tunnels are embedded in soft and compressible soils regardless of the tunneling methods ( [1], [2], [3], [4], [5], [6]). [7] reported that this kind of long-term settlement might last two or more years in saturated soft ground even without any surface loading for Shanghai urban subway tunnel.…”