Study on Interaction Mechanism between Collapsible Loess and the Subway Underground Structure
(1 China Railway First Survey and Design Institute Group Co. Ltd., Xi′an 710043; 2 Shanxi Railway and Underground Traffic Engineering Key Laboratory (FSDI), Xi′an 710043; 3 Chang′an University, Xi′an 710064)
Abstract：
In order to study the interaction mechanism between collapsible loess and underground structure of the metro, the working principle of foundation bearing capacity of metro underground engineering and the principle of earth pressure acting on underground structure in loess stratum were discussed through theoretical analysis based on the experience of underground engineering in loess area. The differences between underground structure as underground hollow structure and general industrial and civil foundation were presented. The variations of base pressure,lateral earth pressure and top earth pressure caused by collapsibility of loess in underground structure of metro were studied through case calculations. The results show that: (1) the working principle of metro underground structure is not applicable to the traditional and classical theory of bearing capacity of foundation soil which is laterally slipping and extruded, and the base pressure generated is less than the self-weight pressure of original base soil and the base is similar to the favorable compensatory foundation in foundation and foundation design; (2) shear strength of loess is a saturated fast shear index at the moment of loess collapsing due to saturated water soaking, the lateral pressure coefficient approaches 1.0 which should be taken into account in design; (3) In loess stratum, if collapsible deformation of soil occurs within the scope of tunnel main body, the vertical earth pressure on tunnel roof increases significantly compared with that without collapsible deformation, which should be considered in design.
2019, Vol. 56 