Key Techniques For Design And Construction Of Metro Station In Loess Strata Using PBA Method

With the rapid development of urban rail transit and underground space technology,the cavern-pile method,as a commonly used construction method for the construction of subway stations,has been applied more and more in the projects with poor ground conditions and large sections.The PBA method has shown significant social and economic benefits in the construction of subway stations in Beijing,Shenyang and Xinjiang,and has excellent development potential and popularization and application value.In this paper,the engineering example of the Guangji Street Station in Xi'an Metro Line 6 is used for numerical simulation by the finite element analysis method to obtain the loess strata pilot tunnel construction scheme and the side pile design parameters in PBA method.The main conclusion of this paper is as follows:(1)In the pilot tunnel construction scheme,the jump digging step distance,the pilot method construction sequence,and the step length have different influences on the ground settlement within the selected research factors and levels.From the perspective of the sensitivity of the ground settlement,the steps length> construction sequence of pilot method> jump digging step.(2)Finally,it is suggested that the optimal parameter combination of the pilot method construction scheme is the jump digging step distance of 12 m + top,bottom,front and back,and the construction sequence + step length of 4m.(3)Under the premise that the side piles satisfies the stability and bearing capacity,the effect of increasing the embedding depth of the side pile to reduce the deformation is not obvious,and the influence of the change in the pile diameter of the side piles on the ground surface settlement is small.The horizontal deformation of the side piles has a greater effect;at the same time,the effect of reducing the surface settlement and the horizontal deformation of side piles is obvious by reducing the center distance of the side piles.(4)The value of the design parameters of the side piles obtained by numerical simulation is: 6m embedded depth + 1.0m side pile diameter + 1.5m pile center distance.