Analysis Of Response Of The Existing Tunnel And Building In Excavation Based On Deformation Control Criterions

Many control criterions of displacement on excavation are collected.According to the command of national codes and regional codes,the fact is: the largest horizontal deformation of excavation in the first orfer is the smaller value between 30 mm and 0.2%H,the largest horizontal deformation of excavation in the second order is the smaller value between 50 mm and 0.3%H,where H is the depth of excavation.Then with considering the small strain stiffness behavior of the soil,the 3D finite element models including the excavation and the building are built.Influence on adjacent buildings and tunnels under excavation is studied.It includes several aspects,such as:(1)The distance between excavation and buildings is set 1.0m,4.5m、9.0m、13.5m、18.0m、22.5m and 27 m.The building is evaluated from the aspect of settlement,angle deformation,deflection ration and maximum principal tensile strain.(2)Isolation walls are constructed between the excavation and building.Then deformation features of buildings are studied in comparison with no isolation walls.(3)According to the practice of deep excavation adjacent to a metro station and a tunnel in Tianjin,five construction schemes are designed to analyze the interactive impact on the adjacent metro station and tunnel caused by bilateral deep excavations using finite element method considering the small strain of soil.It is shown that symmetric excavation method is most optimal to control the deformation of the station and tunnel.Reasonable excavation sequence is effective to control the horizontal deformation of the station and tunnel,however it has no significant effect to control the vertical displacement of the tunnel.For the asymmetric excavation method,it is better to construct a small excavation firstly than a large excavation firstly.(4)Based on LvYinLi project,the deformation of the tunnel is analysed in the process of the first-stage project according to test data.And the deformation of the tunnel in the second-stage and third-stage project is also calculated by the numerical method.At last,influence on tunnels in the scheme of whole excavation is analysed in comparison with two schemes of block excavation.