Abstract:

The auxiliary works of Qingjianglukou station on Line 4 of Chengdu Metro are originally designed to be constructed by cutandcover method. However, most of these auxiliary works are located below the newlybuilt Wenshe viaduct line, therefore mining method is adopted for these auxiliary works. These closespaced mined tunnels have such features as shallow cover, large crosssection, multiple tunneling effect, complex environment and tight construction schedule. Parallel working is achieved for the construction of the auxiliary works by using the opencut foundation pits; countermeasures, including pipe roof supporting, forepoling, radial grouting, sequential excavation and incorporating some steel arches into the secondary lining, are adopted to minimize the multiple tunneling effect. In the end, safe and rapid construction of the auxiliary works are achieved, without influence to the operation of the viaduct line.

Key words: sand and gravel strata, supershallow overburden, close spacing, mined tunnels, auxiliary works, Metro