Abstract: The micro-disturbance construction of box culvert under the condition of large cross-section and shallow cover is a problem to be solved. Hence, 62 square-shaped steel pipe curtains are pre-constructed, and a closed EPB boring machine with the largest cross-section area of 19.84 m × 6.42 m around the world is adopted in the underpass project of Tianlin Road crossing the Central Ring Line in Shanghai. And then the pipe curtain jacking quality control, excavation surface stabilization technology, synchronous propulsion system, special slurry construction technology and microdisturbance construction effect of large cross-section box culvert propulsion construction are introduced. The engineering practice shows that: (1) The closed EPB box-culvert boring machine together with the upper steel pipe curtain forms a double-insurance to the surface Central Ring Line. (2) Soil 15 m ahead of excavation face is affected, which is about 2.5 times the height of the box; and the load-bearing capacity of the upper steel pipe curtain is about 26.5%. (3) Two independent grouting systems of synchronous grouting (grout A) and supplementary grouting (grout B) are established; and the filling coefficient of grouting is chosen as 4 times of the building void, which would induce micro-uplift of pavement. (4) The maximum settlement of the Central Ring Line during the propulsion of the box culvert is ±1 cm, which realize micro-disturbance construction.

Key words: pipe curtain-box culvert, large cross-section, micro-disturbance, surface settlement