On January 23, the left tube of Shiguling No. 1 Tunnel on the Guangzhou New Baiyun International Airport Second Expressway—a Guangdong-Hong Kong-Macao Greater Bay Area infrastructure interconnection project undertaken by China Railway 22nd Bureau Group—was successfully holed through. With this, all 10 mountain tunnels on the project have been completed, laying a solid foundation for the full opening of the line.

Shiguling No. 1 Tunnel is located in Huangpu District, Guangzhou, passing through a provincial-level forest park. It is a separated tunnel with a small clear distance. The left tube is 1,341 meters long and the right tube 1,265 meters long, making it a controlling works of the Airport Second Expressway. An aviation fuel pipeline passes over the tunnel portal; the tunnel body crosses fault fracture zones and shallow-buried, unsymmetrically loaded sections; and the exit end is close to an existing expressway, posing great construction difficulty and high safety risks.

How to ensure project quality under the special construction environment and reduce the impact on the surrounding ecological environment and the operation of the existing expressway became a major challenge during construction.

"When construction reached the ultra-shallow cover section of the tunnel, water seeped from every rock fissure, and broken stones and mud blocks fell from time to time, making construction difficult and safety risks extremely high." To address this, the project department convened expert review meetings, continuously optimized the construction plan, innovated construction techniques, and strictly followed the advance requirements for different surrounding rocks. The excavation method was changed from the double-side drift method to the "three-bench seven-step method," with blasting strictly controlled; at the shallowest cover section, mechanical excavation was mainly used to minimize disturbance to the rock mass and ensure the quality of the initial support of the tunnel.

Because the exit end of the tunnel is close to the already-opened Phoenix Mountain Tunnel of the Guangzhou-Foshan-Zhaoqing Expressway, and the subgrade at the exit end is only 50 meters from the exit of that tunnel and at its nearest point only 18 meters from the Huangpi Village Bridge, and because national law prohibits blasting within 200 meters of an existing expressway, the project team continuously optimized the construction organization plan, stepped up process innovation and safety management, and decided to adopt mechanical crushing plus static crushing. Once conditions inside the tunnel allowed drilling and blasting, protective measures such as blast doors were installed at the portal to protect the operation of the existing expressway. Portal construction followed the principle of accommodating the excavation face, retaining vegetation between the crown interception ditch and the top of the completed tunnel slope, and controlling the extent of exposed slope surface, thereby protecting the surrounding ecological environment to the greatest extent.

The Airport Second Expressway is an important component of Guangzhou's "Four Rings, Eighteen Radials and Fifteen Important Highways" and a key construction project of Guangdong Province. The highway is divided into north and south sections; the north section is already open to traffic, and the south section is about 24 kilometers long. Once completed and opened, the south section will connect with the north section and link seven expressways and high-speed roads, becoming an important highway hub in the Guangdong-Hong Kong-Macao Greater Bay Area. It will focus on upgrading the capacity of the external expressway corridors toward Guanghui, Guang'ao, Guangzhao and Guangqing, helping to build a Pan-Pearl River Delta expressway network centered on Guangzhou and to create a "one-hour traffic circle" in the Greater Bay Area. By then, the drive from Tianhe to Baiyun Airport will be shortened from 1 hour to 30 minutes.