关键词: 盾构隧道, 河床沉降, 防洪墙变形, 土舱压力, 注浆压力, 控制措施

Abstract: Shield tunneling beneath rivers poses various engineering challenges such as soil deformation, surface settlement, and instability threat to river embankments and flood-control walls. To clarify the deformation patterns of soil and flood-control walls during such construction and elucidate the influence mechanisms of construction parameters on deformation, the deformation characteristics of the surface, deep soil layers, and flood walls induced by shield tunneling through the Haihe river of a section of the Tianjin Binhai New Area rail transit line Z4 are analyzed based on actual measurement data. A shield construction process model is established using the finite element software ABAQUS to examine the influence of construction parameters such as soil chamber pressure and grouting pressure. Finally, process control suggestions are proposed for soil pressure balance shield tunneling crossing the Haihe river based on engineering experience and numerical simulation results. The research results indicate the following: (1)  Riverbed settlement is greater than surface settlement, and the settlement of flood control walls is the smallest. (2) The settlement trough at the top of the flood control wall generally follows a Gaussian normal distribution. (3) The flood control wall will experience horizontal displacement towards the direction of tunnel excavation, resulting in a backward tilt with a maximum slope of 0.000 2. (4) The shield tunneling causes a redistribution of internal forces in the flood control wall. The stress on the flood control wall is similar to that of the beam fixed at both ends when subjected to uniformly distributed loads. By simplifying the flood control wall to a beam, the maximum axial force and maximum bending moment of the flood control wall increases by 7 589 N and 841 kN•m, respectively. (5) Increasing the pressure of the soil chamber is beneficial for reducing the settlement of flood control walls and riverbeds, but when the pressure of the soil silo increases to a certain extent, further increases have a limited effect on settlement control, and the effect of grouting pressure on settlement control is relatively small compared to the pressure of the soil chamber. (6) Setting reasonable construction parameters, strengthening oil pressure injection at shield tail and maintenance avoid shield stop at the bottom of the river, and thus ensuring smooth passage of the shield when passing through rivers.

Key words: shield tunnel, riverbed subsidence, deformation of flood control walls, soil chamber pressure, grouting pressure, control measures