Construction Technology and Quality Control of Pushing an Empty Shield Through a Mining Excavated Tunnel

The shield tunneling method is widely used in the construction of urban underground tunnels due to its high degree of mechanization, minimal impact on the surrounding environment, and high construction efficiency. However, during construction, shield tunneling often cannot be started using conventional techniques due to the size of the starting well and adverse geological conditions.This paper explores the application of the shield non-excavation stepping and split-start technology in a specific shield tunnel section of Guangzhou's rail transit system. This technology overcame the challenges posed by the small size of the launching shaft and the traversal of hard rock strata, significantly enhancing the construction efficiency of the shield's initial launching. On-site, medium-coarse sand was used as the backfill material instead of the conventionally used pea gravel. Through precise calculations of construction resistance, optimization of tunneling parameters, and grouting techniques, the occurrence of quality issues such as segment misalignment, leakage, and axis deviation in the non-excavation section of the tunnel was effectively reduced. The successful application of the shield non-excavation stepping and split-start technology in this project achieved excellent engineering results, providing valuable references for similar projects.