In this study, the deep foundation pit project of No.4 Wangjiang New City of Hangzhou New World is taken as a case study, and the zonal excavation process of the foundation pit is comprehensively monitored. Through the in-depth analysis of the monitoring data of the diaphragm wall deformation, soil inclinometer measurements, wall top settlement, and ground settlement outside the pit, and combined with the numerical model of the foundation pit zonal excavation established by PLAXIS 3D, we compare the numerical simulation results with the actual monitoring data to validate the accuracy of the model and to supplement the insufficiency of the monitoring data. The results show that the deformation of the diaphragm wall during the excavation of the foundation pit presents a typical parabolic variation pattern, and a push-back displacement toward the pit occurs during the post-excavation construction stage. The deformation characteristics of the soil outside the pit are similar to those of the diaphragm wall, but its deformation magnitude is relatively small. With the progress of foundation pit excavation, the ground settlement outside the pit increases gradually, and its displacement curve deviates from the traditional parabolic variation pattern due to the influence of environmental factors. In addition, the wall top settlement shows a clear trend of “first heave and then settle” during the foundation pit excavation and the construction of the main structure inside the pit.

It is difficult to control the plane posture of shield tunneling machines during construction on small radius curved sections. In actual construction, construction person mainly determine the main parameters based on experience, and there is currently no relevant theoretical basis. This article analyzes the plane posture of shield tunneling machines and proposes a reasonable plane state for shield tunneling machines, that is, the cutter head of the shield tunneling machine passes through curved sections close to the outer boundary; When obtaining a reasonable plane posture of the shield tunneling machine, the relationship between the inner and outer jack travel of the shield tunneling machine can be obtained. During construction, as long as the pushing amount of the inner jack is controlled, the pushing amount of the outer jack can be obtained; A reasonable calculation method for the maximum over excavation amount of the shield machine under different top pushing amounts in the plane state of the shield machine is obtained; It is proposed to only perform over excavation on the inner side of the curve, without over excavation on both the upper and lower sides, and a calculation method for the extension of the over excavation knife at different angle positions is obtained. The results have laid the theoretical foundation for intelligent control of shield tunneling posture in curved sections.

The foundation pit excavation and dewatering break the equilibrium stress field of the surrounding soil layer and negatively affect the underlying shield tunnel. The analytical solution of the longitudinal deformation of the underlying tunnel caused by foundation pit excavation and dewatering is proposed using a two-stage analysis method. In the first stage, Mindlin elastic solution and effective stress principle are used to calculate the additional stress caused by excavation and dewatering. In the second stage, the shield tunnel is treated as a Timoshenko beam resting on the Pasternak foundation to simulate the interaction between the tunnel and soil. The analytical solution of the longitudinal tunnel deformation is derived from the superposition method. By comparing with the monitoring data of engineering examples, the correctness of the proposed method is verified, and the influence of the excavation length, width, depth, tunnel burial depth, dropdown, and relative position of the foundation pit on the longitudinal displacement of the tunnel is further analyzed. The results show that with the increase of excavation length, width, and depth, the maximum uplift of the tunnel increases. The tunnel deformation decreases with the increase in tunnel burial depth. With the increase of the dropdown, the uplift decreases, and the settlement value increases. With the increased distance between the tunnel axis and the foundation pit center, there are a decreasing area of the uplift, an increasing area of the settlement, and a decreasing area of settlement.