On August 18, the Zaojiaoping Tunnel, a key control project on the Zhengxi Expressway, was successfully holed through. It is understood that the Zaojiaoping Tunnel in Contract Section 11 of the Zhengxi Expressway crosses a mountain ridge with a maximum burial depth of more than 315 meters. With complex geology and poor surrounding rock grades, it is a shallow-buried unsymmetrical-loading tunnel, posing extremely high construction risks. The tunnel is 2.4 kilometers long, accounting for 40.2% of the route length, and is a key control project on the entire line. Since entering the site, the tunnel construction unit has assembled elite forces and successively overcome a series of difficulties, including the difficulty of tunneling through the shallow-buried portal section, unsymmetrical loading of the small-clearance tunnel, landslides at the entrance mountain, and rockfall in the tunnel's bedding fracture zone. The three-bench seven-step method was adopted for excavation, the wet spraying process for initial support, and stainless steel hydraulic formwork trolleys for secondary lining. Strict controls were enforced to ensure both construction progress and safety and quality.
Since the start of tunnel construction, the construction unit has vigorously promoted site standardization, construction standardization, and management standardization. It has adopted tunnel wet spraying technology, standardized process cycles, strengthened monitoring and measurement, and vigorously pursued advanced geological forecasting, while strictly enforcing on-site safe and civilized construction and quality control. The standardized construction process of "advanced pipe forepoling, strict grouting, short excavation, strong support, early closure, and frequent measurement" was strictly followed. Key processes such as arch frame installation, initial support shotcrete, waterproofing lap joints, invert excavation, and concrete pouring were strictly controlled, achieving the goals of zero safety accidents and zero quality defects, ensuring the successful holing through of the Zaojiaoping Tunnel and laying a solid foundation for the early opening of the Zhengxi Expressway.