Given the increasingly notable segmentation of underground space by existing subway tunnels,it is difficult to effectively and adequately develop and utilize underground space in busy parts of a city.This study presents a combined construction technology that has been developed for use in underground spaces;it includes a deformation buffer layer,a special grouting technique,jump excavation by compartment,back-pressure portal frame technology,a reinforcement technique,and the technology of a steel portioning drum or plate.These technologies have been successfully used in practical engineering.The combined construction technology presented in this paper provides a new method of solving key technical problems in underground spaces in effectively used cross-subway tunnels.As this technology has achieved significant economic and social benefits,it has valuable future applications.
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