Abstract:

The excavation and secondary lining of flatroof straightwall tunnels with shallow overburden have great risks. In the paper, the applicability of the flatroof straightwall tunnels is analyzed. Three methods for the installation of the secondary lining of flatroof straightwall tunnels are compared in terms of span, excavation method, risk and construction period, with a mined flatroof straightwall underpass of a Metro works as an example. The advantages, disadvantages and application conditions of the mentioned three methods are summarized. The installation method and steps for the secondary lining of mined flatroof straightwall structures under the condition that the support is not removed are proposed. The key points of the design of mined flatroof straightwall tunnels are summarized and the principle for the node treatment is proposed.

Key words: underground structure, mining under shallow cover, flat roof, straight wall, secondary lining