At 9 a.m. on September 19, amid resounding blasts, after more than 600 days and nights of continuous effort, the left tube of the Dongyueguan Tunnel was successfully holed through. This tunnel is the only low-gas tunnel on the Lu Hongshan (Hunan-Hubei border) to Cili section of the national key project G59 Hohhot-Beihai Expressway, built by China Railway Communications Investment Group and constructed by China Railway Tunnel Group Co., Ltd. This marks another major milestone breakthrough following the holing-through of the Cili Tunnel on August 11, a key and difficult control project on the entire line, laying an even more solid foundation for the smooth opening of the Lu-Ci Expressway.

The Dongyueguan Tunnel is a small-spacing tunnel, with a left tube 3,690 m long and a right tube 3,688 m long; it is an extra-long tunnel on a 100 km/h dual-carriageway, four-lane expressway. Because nest-shaped coal deposits are locally developed in the strata of the tunnel area, the tunnel passes through low-gas sections for up to 460 m. The gas emission volume from geological exploration is the highest in the Lu-Ci Expressway project, making it the only low-gas tunnel on the Lu-Ci Expressway.

To ensure that construction remained under control and to efficiently solve construction difficulties, the Lu-Ci Expressway Project Department of China Railway Tunnel Group Co., Ltd. strictly carried out gas detection from the very start of tunnel excavation, tightening the valve on work safety. In accordance with the requirements for gas tunnel construction, they prepared a gas tunnel safety management system, temporary power supply for high-gas tunnels, advanced geological forecasting, construction ventilation, gas safety monitoring, special construction plans, emergency response plans, and so on. Combining geophysical and drilling results, they conducted regular comprehensive forecasting of potential gas content, pressure, and emission volume, established an all-weather gas monitoring and control system, and continuously used mechanical ventilation to prevent local gas accumulation in the tunnel, successfully and safely passing through potential gas zones.

At the same time, the Dongyueguan Tunnel passes through clastic rock and carbonate rock, and tunnel construction faces special geological problems such as karst and karst groundwater, and dissolution-fractured zones. To effectively prevent risks such as flat-arch formation, separation failure, and collapse and block falling in the tunnel, the Lu-Ci Expressway project has always upheld the new-era tunnel spirit of "overcoming difficulties, being willing to dedicate, and having the courage to win" and the corporate spirit of "utmost precision and sincerity, better and newer." It strictly follows the principle of "support immediately after excavation, spray first and anchor afterward," scientifically optimizes the crown excavation blasting parameters to reduce the number of disturbances, strictly controls overbreak and underbreak, strengthens advanced support design, installs "jacks" for weak interlayers, and effectively resolves the safety risks existing in tunnel construction.

The successful holing-through of the left tube of the Dongyueguan Tunnel this time has greatly boosted the morale of all project participants. The Lu-Ci Expressway has fully sounded the call to forge ahead. The participants will, with greater enthusiasm, greater determination, a higher level, and stronger efforts, accelerate construction progress while ensuring quality and safety, and deliver a satisfactory result for the smooth opening of the expressway.