Abstract:

The running tunnel from Luogang station to Xiangxue station on Line 6 of Guangzhou Metro crosses ground containing boulder groups, therefore the shield has great risks in the boring of the running tunnel. In the paper, the forming mechanism of the weathered granite boulders is presented, the ground surface settlement, shield attitude control and equipment risks are studied, and the limitations of the conventional boulder treatment methods are analyzed. Conclusions drawn are as follows: 1) Systematic scheme including boulder pretreatment, shield boring and cutter replacement should be considered when shield bores through ground containing boulder groups; 2) Preblasting the underground boulders on the tunnel route can reduce the risks of shield boring, and the shield boring parameters must be strictly controlled when the shield bores through the ground containing boulders; 3) The consolidation of the ground around the cutterhead by means of compaction grouting, water sealing at the shield tail and forming filter membranes in the chamber are helpful to the cutter replacement under hyperbaric conditions. 

Key words: shield tunneling, boulder group, blasting, compaction grouting, hyperbaric operation, boring parameters