Influences On The Surface Structure And Special Environment Induced By Shield Tunneling

In this paper, the impact of grouting pressure deviation and surface building caused by shield tunneling is investigated. To analyze the shield excavation impact mechanism and protection of the building, the field data research methods and numerical simulation research is used. The main contents and conclusions are as follows:1) According to the construction of Tianjin Metro Line 2 passing under a masonry building, the finite element model is established to analyze the influence of tunneling on the ground surface and the surface masonry buildings. The calculated results which adopt the small-strain constitutive model are compared with the field measured data. The results are also compared with the conclusions which obtained by the hardening soil constitutive model. The further analysis shows that both the maximum settlement and the width of traverse settlement trough predicted by small-strain model achieved better agreement with the practical project. And both the maximum settlement and the width of traverse settlement trough obtained by the hardening soil model are bigger than the results which are obtained by the small-strain constitutive model. During the tunnel construction, the masonry building tilts to the axis of the tunnel. The rate of inclination obtained by the small-strain model can also consistent with the field data. Therefore, the small strain response of soil should be taken into account during the settlement investigation of buildings and ground surface induced by shield tunnel.2) To analyze the influence on the surface subsidence and surface building caused by shield tunneling, the Plaxis finite element modeling software is used and the finite model is based on the Cheng-jin-da construction cases. The main conclusion is as follows: the closer the distance between the tunnel axis and the monitoring points arising from the greater settlement, and the percentage of the settlement generally generated by tunneling beneath is less than what the above tunnel excavation produced. During the shield tunneling, longitudinal differential settlement is serious. After the shield machine passes, uneven settlement gradually eliminated. The transverse differential settlement remains unchanged after it achieves maximum settlement.3) Through the research on the effects of different angles of the building, the results are as followings. With the increases of the crossing angle, the foundation settlement of Xishan wall increases and the rate of inclination decreases. And with the increases of the crossing angle, the foundation settlement of Nan side wall decreases and the rate of inclination increases. With the increasing of the angle, the building wall that is perpendicular to the axial direction of the shield is not affected, but parallel to the axis of the shield has a greater slope of the adverse effects.4) The control of the shield tail grouting is one of the important factors affecting soil deformation. Therefore, when shield tail grouting appeared pressure deviation respect to the status of normal, the influence of top soil and surface deformation is investigated. The number of rings for different grouting pressure is simulated to investigate the impact of soil deformation.