Research on the Construction Scheme of Underground Transportation Hub Based on the Combined Method of Cover and Open Excavation

In order to meet the need of the urban road above the underground traffic hub of Beijing sub-center put into operation first, a construction scheme combining cover excavation and open excavation is proposed. The main characteristics of the scheme are as follows: 1) The foundation pit of the underground transportation hub is divided into three parallel layout pits, namely “cover excavation pit, open excavation pit and slope excavation pit”;2) The supporting structure is shared between cover excavation pit and open excavation pit; 3) First, the roof structure construction of the cover excavation area is completed to resume the urban road operation as soon as possible, and the negative layer construction of the cover excavation area is carried out by the reverse method, and then the open excavation pit and the slope excavation pit on both sides of the cover excavation area are simultaneously excavated; 4) The negative second floor and negative third floor of the cover excavation area is constructed by open excavation method. The paper elaborated the construction procedure of the combined method of cover cut and open cut and analyzed the advantages of the combined method. Considering that the steel tube column in the cover excavation area is always disturbed by the excavation of the foundation pit, the deformation law of the steel tube column during the excavation of the foundation pit is analyzed by the numerical simulation method combined with the site monitoring results. The results show that the horizontal deformation and uplift deformation of steel tube column meet the control requirements. The combined construction scheme of cover cut and open cut proposed in this paper can not only ensure that the urban roads in the underground transportation hub area can be put into operation as soon as possible, but also each foundation pit excavation and structure pouring are basically independent of each other, effectively reducing the mutual influence of the foundation pit construction in cover cut area and open cut area, and improve the construction efficiency.