Key Technology of Metro Tunnel Passing Through Soft-Hard Combined Water-Rich Sand Layer
The tunnel body of Qingdao Metro Line 1 in Zhongsheng section is located in the rock stratum because of the shallow depth and the overlying rock of the arch is only 0.3-2.2 m,which belongs to a typical soft-hard combined arch water-rich sand stratum geology for it used to be a beach land,with thick sand layer on the surface and rich in water.In view of this kind of special geology,grouting is the most commonly used method to control this kind of geological disaster,but the grouting construction in the water-rich sand layer is in the blind and experienced stage for a long time,and the grouting design lacks the theoretical basis,the effect of grouting reinforcement can not be guaranteed effectively,because of the complex urban environment,the safety of tunnel construction can not be guaranteed.In this project,advanced replacement grouting in water-rich sand layer is used to reinforce the arch stratum and anti-step controlled blasting technology is used to peel off layer by layer to reduce the repeated disturbance to the arch bad geology and fully ensure the self-supporting ability of the stratum,thus ensuring the safety of excavation.This technique can be used for reference in the construction of metro tunnel under the condition of water-rich sand layer in soft-hard combined arch.
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