Abstract For the subway station constructed with cut and cover top-down method, the vertical supporting system used during the construction is composed of the foundation pit supporting structure, intermediate column and pile foundation under the column, and the stability of the vertical supporting system is the key to the success of the project. Since the intermediate pile foundation bears the roof casingsoil, the dead weight of the roof and the intermediate floor structure, the road vehicle load and the construction load, etc., the selection, bearing capacity and settlement calculations of the intermediate pile foundation should be carried out according to the engineering geological conditions, the layout of the column network, the type of intermediate column and the construction requirements. Taking Zhongnan Road Station of Wuhan Metro as an example, comparison among four schemes of the pile foundation under column for the vertical support system of the station with cut and cover top-down method is conducted in this paper. By analyzing the bearing capacity, settlement, construction period and economic requirements of the intermediate pile foundation, it is finally decided to use the scheme of screw-drilled under-reamed hydraulically cast-in-situ pile for construction. The pile test on the site, construction feedback, and deformation monitoring results show that the settlement of each pile top is no more than 3.7 mm and the ground settlement is 6.45 mm during construction after the technology of screw-drilled under-reamed hydraulically cast-in-situ pile is used, which can meet the settlement control requirements for pile body and surrounding buildings very well. Besides, with a lower cost and shortest construction period, the scheme of screw-drilled under-reamed hydraulically cast-in-situ pile is the best one for Zhongnan Road Station of Wuhan Metro.
Abstract：
For the subway station constructed with cut and cover top-down method, the vertical supporting system used during the construction is composed of the foundation pit supporting structure, intermediate column and pile foundation under the column, and the stability of the vertical supporting system is the key to the success of the project. Since the intermediate pile foundation bears the roof casingsoil, the dead weight of the roof and the intermediate floor structure, the road vehicle load and the construction load, etc., the selection, bearing capacity and settlement calculations of the intermediate pile foundation should be carried out according to the engineering geological conditions, the layout of the column network, the type of intermediate column and the construction requirements. Taking Zhongnan Road Station of Wuhan Metro as an example, comparison among four schemes of the pile foundation under column for the vertical support system of the station with cut and cover top-down method is conducted in this paper. By analyzing the bearing capacity, settlement, construction period and economic requirements of the intermediate pile foundation, it is finally decided to use the scheme of screw-drilled under-reamed hydraulically cast-in-situ pile for construction. The pile test on the site, construction feedback, and deformation monitoring results show that the settlement of each pile top is no more than 3.7 mm and the ground settlement is 6.45 mm during construction after the technology of screw-drilled under-reamed hydraulically cast-in-situ pile is used, which can meet the settlement control requirements for pile body and surrounding buildings very well. Besides, with a lower cost and shortest construction period, the scheme of screw-drilled under-reamed hydraulically cast-in-situ pile is the best one for Zhongnan Road Station of Wuhan Metro.
CHEN Liang
.Study on Selection of the Intermediate Pile Foundation of Subway Stations with Cut and Cover Top-down Method[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(2): 166-173
2021, Vol. 58 