RBJ for sizable underpass construction in saturated soft soils

The non-excavation technology was adopted for the construction of a six-lane underpass section of Shanghai Middle Ring Project after taking into account the environmental and existing ground conditions. To construct a sizable underpass in saturated soft soil, surface subsidence control is required. The underpass section with shallow overburden of 4.5-5m has a length of 126m, a width of 34.2m and a height of 7.85m. A new method named Pipe Roof-Box Culvert Jacking (RBJ) therefore was proposed for the building of the underpass structure. The pipe roof was composed of 80 pieces of 970mm pipes and constructed by slurry pipe jacking method. This worked like a guide tunnel, whereas the box culvert jacking was constructed inside the pipe roof structure. This new method has advantages of being reliable and cost effective. This paper elaborates the key technologies and the main procedures involving this new method. The mechanism and result of the method is discussed based on the data of site instrumentation. This paper could be used as a reference for both construction and design of similar projects in future. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. "Reprinted with permission from Elsevier".