Mechanical analysis and field measurement of large-section rectangular pipe jacking buried deep in soft soil

Deeply buried large-section rectangular and quasi-rectangular pipe jacking are increasingly used in the construction of large-scale urban underground structures such as soft soil subway stations. The water and soil load characteristics and structural stress performance of this new structure play an important role in ensuring the long-term safety of urban underground spaces. However, Relevant research is still limited. This study relies on the Jing'an Temple Station Project of Shanghai Rail Transit Line 14, combined with on-site measurements and theoretical analysis, to study the spatial distribution characteristics of water and soil pressure and force response of a large-section rectangular pipe-jacking structure deeply buried in soft soil, and comparatively analyzes the spatial distribution characteristics of different soils. The applicability evaluation of the design theory was carried out based on the influence of pressure theory and soil-structure interaction mode on the internal force response of pipe jacking structures. The main conclusions are: (1) The measured vertical earth pressure is close to the theoretical value considering the soil column weight, and the bending moment of the structure calculated by using the above theoretical earth pressure is consistent with the field measurements, reflecting that the soil arching effect at the top of the pipe jacking in this project may not be significant; (2) The bending moment of the quasi-rectangular jacking pipe shows a "butterfly-shaped" distribution, indicating that the deformation mode of the structure is vertical concave and transverse convex; the transverse convexity of the waist on both sides leads to the generation of obvious formation horizontal resistance; (3) The horizontal resistance of the formation has a significant impact on the internal force of the large-section rectangular pipe jacking structure. Existing pipe jacking structure design specifications mostly ignore this factor, which can lead to an overestimation of the structural bending moment. In the waist areas on both sides of the structure, the average error can exceed 2 times.