The Chengkai Expressway connects Chengkou County and Kaizhou District in Chongqing City. It is a section of the national G69 Yinbai Expressway (from Yinchuan to Baise), with a total length of 129.3 kilometers. This road has many bridges and tunnels, accounting for 81% of the entire route, with a designed speed of 80 kilometers per hour and four lanes in both directions.
One particularly long tunnel on the Chengkai Expressway has a length of 11,489 meters for the left line and 11,456 meters for the right line. Ventilation, drainage, treatment of poor geological conditions, construction of inclined and vertical shafts, and measurement control are all key and difficult points during construction.
The Chengkai Tunnel passes through the Xuebaoshan National Nature Reserve, so a zero-excavation approach was adopted during construction to minimize damage to the original mountain. Previously, for aesthetic reasons, tunnel entrances would be built in a flat shape, requiring extensive excavation of the mountain, which could easily cause disturbances to the mountain and lead to geological disasters such as landslides at the tunnel entrance. However, the Chengkai Tunnel directly enters the mountain for excavation based on the terrain characteristics, better preserving the natural landscape of the mountain.
The LanHi Intelligent Arch Spray Integrated Trolley is a tunnel construction equipment jointly developed by Blue Ocean Zhizhuang and Sichuan Road and Bridge Tunnel Branch. It adopts a structure with an engineering chassis, four-wheel drive, four-wheel steering, and front and rear bidirectional driving. The upper part is equipped with three arms with full sliding movement, three gripper hands, two baskets, two undercut hammers, and two anchor arm structures, enabling seamless connection of various construction processes during tunnel construction, thereby improving construction efficiency and reducing safety hazards and occupational injuries.
The Chengkai Tunnel is the first highway tunnel project in the country to achieve fully mechanized assembly construction. Additionally, it adopts the most advanced domestic information management system and conducts comprehensive monitoring at the construction site. On March 31, 2022, the Chengkai Extra-Long Tunnel was fully penetrated, achieving an important milestone.