Abstract:After analyzing and comparing the advantages and disadvantages of different construction methods under similar environments and stratum conditions, the rock rectangular-like pipe jacking method is applied in the Chongqing Tiangongdian Underpass Expressway Project for the first time. The pipe jacking machine is an innovative composite equipment with multi-cutterhead + roller excavation, which verifies the feasibility of rectangular-like pipe jacking in composite strata of excavation backfill and rock, and realizes the reaction force starting from the pile-raft reinforced concrete structure in the section of the embankment without vertical shafts. In the slope-adjacent section, the pipe jacking machine is received under the restricted conditions by embedding pipe roofs under the subgrade, extending the shed tunnel structure, and using longitudinal/horizontal slipping. The turnover device of pipe segments is researched and developed. The semi-circular pipe segment test is tried. The caulking on the backwater surface of pipe segments is eliminated. The control measures for the tunneling in the rock sections and backfill soil or rock strata that are soft on top and hard at the bottom are explored. The emergency response is handled for abnormal situations such as ground subsidence, obstacles and mud leakage. The new design and construction solutions are proposed for tunnels passing through the backfill soil and shallowly covered rock under the condition that the surrounding environment must be strictly controlled.
