Shield construction in structural soft soils inevitably disturbs the soil around the tunnel leading to tunnel settlement instead of tunnel uplift due to soil unloading rebound during construction. In this paper, tunnel settlement prediction in structural soft soils during construction has been studied by adopting Oujiang Beikou shield tunnel as an example. Firstly, disturbance degree calculation method based on effective stress was introduced and the disturbance degree due to shield construction was numerically simulated. Secondly, combined with one-dimensional consolidation test results, a “two-fold line” settlement calculation model was developed for disturbed soil. Finally, tunnel settlement during construction was predicted through one-way compression layer-summation method and compared with experimentally measured results. Research results demonstrated that the developed method was suitable for the prediction of shield tunnel settlement in structural soft soils.

In order to study the deformation of a diaphragm wall and the settlement of surrounding soil under the complicated conditions of the deep and soft soil layer, which is underlying inclined rock and top‐down construction method, the construction scheme of suspended diaphragm wall based on the engineering practice of Oujiang North Estuary deep and large foundation pit of Wenzhou S2 railway is proposed, and the research method of numerical simulation is adopted in this article. By using Midas GTS finite element software, a three‐dimensional model of deep and large foundation pit excavation with top‐down construction method is established, and the internal force, deformation, and surface settlement of surrounding soil of suspended diaphragm wall with different depths into rock (1 m, 2 m, and 4 m) are analyzed. Furthermore, the optimization simulation research on the anchor locking scheme is carried out for the determined footed diaphragm wall. Similarly, the anchor locking scheme at a depth of 1 m into the interface between soil and rock is selected as the supporting scheme of the footed diaphragm wall through the simulation results. The research results of this article can guarantee the safety of diaphragm wall construction of deep and large foundation pit in complex stratum.

In order to study the construction effect of deep and large foundation pit excavation and its impact on the surrounding environment under complex stratum conditions, the deep and large foundation pit of the top‐down construction method of shield exit shaft of S2 line of Wenzhou City railway is taken as the research object in this paper. According to the complex geological conditions of deep soft soil layer with underlying inclined rock surface in Wenzhou, the numerical simulation method is used to carry out the related research. The simulation results of the deformation characteristics of the diaphragm wall under two different working conditions which are the same length diaphragm wall and the suspended foot diaphragm wall are compared and analyzed. According to the analysis results, the suspended foot diaphragm wall is determined as the final construction scheme of the diaphragm wall, and it is verified by field measurement. The research results can provide technical support for the construction of similar projects. At the same time, it can also provide basic accumulation for the construction of major projects in Wenzhou.