下穿九圩港河的盾构隧道开挖面稳定性研究

Research on Excavation Surface Stability of Shield Tunnel under Jiuweigang River

依托南通地铁盾构下穿九圩港河项目,建立非均质、各向同性地层中盾构隧道开挖面稳定性的三维楔形体理论。考虑地下水的作用,推导粉砂层盾构隧道开挖面土体处于主动破坏状态(沉陷)时的最小支护应力计算公式,以及处于被动破坏状态(隆起)时的最大支护应力计算公式,编制相应计算程序,计算下穿九圩港河隧道区间200环处和323环处的盾构支护应力。与经验公式相比,三维楔形体理论的计算结果与实际掘进土仓的压力值更吻合。此外,讨论不同隧道埋深与直径比(H/D)时,地层的黏聚力和内摩擦角对支护应力的影响,结果表明:随着地层黏聚力、内摩擦角的增大,最小支护应力减小;H/D值对最小支护应力的影响较大,随着H/D值的增大,最小支护应力显著增大。研究成果可为隧道工程设计提供可靠的理论依据。

Based on the project of Nantong subway shield underpassing Jiuweigang River,the three-dimensional wedge theory of shield tunnel excavation face stability in heterogeneous and isotropic strata is established.Considering the effect of groundwater,the calculation formula of the minimum supporting stress when the soil of shield tunnel excavation face in silty sand is in the active failure state(subsidence)and the calculation formula of the maximum supporting stress when the soil is in the passive failure state(uplift)are derived.The corresponding calculation program is compiled to calculate the shield support stress underpassing 200 and 323 rings of Jiuweigang River Tunnel.Compared with the empirical formula,the calculation results of the three-dimensional wedge theory is more consistent with the actual excavation earth pressure value.Furthermore,the effects of cohesion and internal friction angle on support stress with different ratio of tunnel depth to diameter(H/D)are discussed.The results show that the minimum support stress decreases with the increase of cohesion and internal friction angle,and the value of H/D has a great influence on the minimum support stress,and the minimum support stress increases significantly with the increase of H/D,which can provide a reliable theoretical basis for tunnel engineering design.