Abstract:

A special doublesidedrift method, of which the doubleside drifts are completed before the excavation of intermediate diaphragm wall, is analyzed so as to guarantee continuous and safe shield construction by taking Shangqiao Station of loop line of Chongqing Metro for example. The excavation stability of rock column of temporary intermediate diaphragm wall and reinforcing technology are discussed and key construction technologies for rock column excavation of temporary intermediate diaphragm wall are proposed. The analytical results show that large settlement and convergence had occurred to tunnel crown top before the excavation of rock column of temporary intermediate diaphragm wall. In order to guarantee the excavation of rock column of temporary intermediate diaphragm wall and control the deformation of tunnel, the rock column of temporary intermediate diaphragm wall and the tunnel are reinforced; and bench method is adopted. The forcing mode of primary support can be improved and the tunnel convergence can be controlled by using footlock anchor bolt at arch of intermediate diaphragm wall around the crown and increasing the stiffness of temporary support system of intermediate diaphragm wall.

Key words: doublesidedrift method, large crosssection intermediate diaphragm wall, stability, numerical simulation, construction control