天津站地下换乘中心基坑工程2标段盖挖逆作法的实测分析

分析了天津站地下换乘中心工程2标段基坑开挖过程中的地下连续墙水平位移、结构柱隆沉及其差异变形和主动区土压力的监测结果．实测表明：当开挖完成后，普通地下连续墙最大侧移位置位于开挖面附近，而T形地下连续墙．即使开挖至负4层，最大侧移位置仍在开挖面之上的墙体中部．开挖过程中墙体侧移会出现由于开挖的空间效应而减小的情况．结构柱隆起具有明显的时空效应，其值与距地下连续墙的距离、层板浇筑、开挖顺序等因素有关．尽管最大隆起超过控制值，但差异变形在控制范围内且结构并未破坏，可以适当放宽结构柱隆起预警值的要求，以差异变形为关键控制标准．墙外主动区土压力呈曲线分布，在施工过程中变化较小，其分布及变化与墙体挠曲形式和侧移趋势有关．

Analysis on Monitoring of Top-Down Method of Section 2 of Tianjin Railway Station Underground Transfer Centre

The analysis was conducted on the monitoring data of the excavation for section 2 of Tianjin railway sta- tion underground transfer centre. The data included horizontal displacement of diaphragm wall, heave and differential displacement of columns and earth pressure in the passive zone. It was shown that the position of the maximum hori- zontal displacement of normal diaphragm wall occurred at the exaction bottom when the excavation was completed. However, for the T-shaped diaphragm wall the maximum horizontal displacement occurred at the middle of the wall above the excavation bottom even through the fourth underground story had been completed. The horizontal displace- ment of diaphragm wall during the excavation would be reduced due to the spatial effect of excavation. The heave of columns had an obvious space-time effect. The heave was closely related to distance between the column and the dia- phragm wall, slab pouring, excavation sequence, etc. Although the maximum heave exceeded the control value, the differential deformation was still in the control range and the structure was not damaged yet. So the request of heave alarm value for columns could be relaxed appropriately and the differential deformation could be chosen as the key control criterion. The earth pressure in the active zone, the distribution and variation of which being related to the flexure form and lateral displacement trend, presented curve distribution and changed slightly during the construc- tion.