On October 9, the twin tubes of the Guangyi Tunnel of the Guangxi Cangzhao Expressway Project, constructed by China Construction Second Engineering Bureau, were successfully holed through.

The Guangyi Tunnel is a key controlling works of the Guangxi Cangzhao Expressway Project. It is a separated long tunnel built to the standard of a two-way four-lane expressway with a design speed of 100 km/h. Its left tube has a total length of 1,593 meters and its right tube a total length of 1,574 meters.

The Guangyi Tunnel is a separated two-way four-lane expressway tunnel with a small spacing between the left and right tubes; the distance between the two portals is only 12.75 meters. The portal overburden is shallow, making tunnel entry difficult, and the left portal is subject to severe unsymmetrical loading. It is a typical shallow-buried tunnel with unsymmetrical loading and a small clear distance, which posed enormous obstacles to the portal construction.

Following expert verification, the tunnel was constructed using the New Austrian Tunnelling Method (NATM). On the premise of utilizing the inherent load-bearing capacity of the surrounding rock, millisecond blasting and smooth blasting techniques were adopted for full-face excavation, and a composite two-layer inner and outer lining was formed to build the tunnel bore. During construction, the project adopted fully mechanized supporting equipment for all processes, greatly improving work efficiency and quality, process standards, and safety management.

The holing-through of both tubes of the Guangyi Tunnel is a successful practice of the NATM. Upon completion, the tunnel will shorten the distance from Guangning via Cangwu to Zhaoping and further optimize Guangxi's transportation network. Once the Guangxi Cangzhao Expressway Project is completed, it will also interconnect with expressways such as the Erguang, Guangkun, Shankun, Baomao, and Guangfozhao expressways, forming a well-connected eastward-integration road network, helping Guangxi deeply participate in the construction of the Guangdong-Hong Kong-Macao Greater Bay Area, and further promoting the development of the Pearl River-Xijiang Economic Belt.