[Objective]Determine the limit support pressure required to maintain tunnel face stability during the construction of double-line small clearance shield tunnel.[Method]The excavation stability of double-line small clearance shield tunnel is studied by using a combination of numerical simulation,the-oretical analysis and engineering verification.Numerical simu-lation is used to analyze the instability mode and limiting sup-port pressure of double-line small clearance shield tunnel face.Based on the numerical simulation results,an analytical model for the instability of a double-line shield tunnel excavation face is proposed,and the limit support pressure required to maintain the tunnel face stability is derived by using the limit equilibrium theory.[Result & Conclusion]During the construction process of the small-clearance shield tunnel,a combined soil arch will be formed.Under the action of the combined soil arch,the limit support pressure required to maintain the stabili-ty of the double-line small-clearance tunnel excavation surface will increase significantly.Theoretical analysis shows that when the clearance is less than 0.5 D(D is the tunnel diame-ter),the limit support pressure increases with the increase of the clearance;when the clearance exceeds 0.5D,the limit sup-port pressure decreases with the increase of the clearance;when the clearance exceeds 2.0D,the combined soil arch cannot be formed,and the failure mode in this case is the same as that of the single-hole tunnel,and the clearance no longer affects the limit support pressure.
关键词
地铁/双线隧道/小净距/开挖面稳定性/极限支护压力
Key words
metro/double-line tunnel/small clearance/ex-cavation face stability/limit support pressure
维普
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