On January 11, the Houci Tunnel on the Xiamen-Chengdu Expressway, China's first medium-length mountain tunnel expanded from two to four lanes, completed asphalt pavement paving, marking the project's full completion and official entry into line marking construction. The tunnel is expected to open to traffic by the end of January together with the Shizhong-Hongfang section of the Xiamen-Chengdu Expressway reconstruction and expansion project!


The Houci Tunnel is a controlling project of the Longyan Xiamen-Chengdu Expressway expansion project. Located in Shizhong Town, Xinluo District, it was constructed by the Fifth Company of China Railway 15th Bureau Group. The tunnel was expanded from two lanes to four lanes in situ on the right line of the original Houci Tunnel of the Zhanglong Expressway. With a length of 1,002 meters, it is a medium-length large-span tunnel. Its width was expanded from 9 meters to 20 meters, and the clearance after expansion is 17.75×5 m (width×height). The tunnel is 1,002 meters long and is the first two-to-four-lane tunnel in mountainous areas nationwide and in the province.

The project started on November 25, 2017. The geology is quite complex, with cavities, accumulation bodies, and strongly weathered rock. The tunnel had already been blasted once during previous construction; the geology is soft, and the rock turns into soft mud when encountering water. Construction team leader Chen Xingyi, a native of Chongqing, has built dozens of tunnels across the country and had never seen a tunnel so difficult.

After construction entered the tunnel, collapses and cavities were encountered. The entire project experienced more than 40 collapses, the largest with a volume of over 3,000 cubic meters. After a collapse, the area was first sealed and directly filled with concrete, and excavation resumed after stabilization. In one case, the collapse reached 30 meters high and broke through completely; 2,000-plus cubic meters of concrete were poured to seal it. For the entire project, concrete usage alone increased by more than 30,000 cubic meters.

Lei Hui, the person in charge of the construction contractor, introduced that the most difficult period was the "collapse through to the surface" from June 22 to 24, 2018. The construction team urgently carried out drainage ditches to prevent the collapse area from expanding, then began grouting, washing out the loose slurry, and pumping concrete. Project manager Wang Xiaorong and construction team leader Chen Xingyi were on duty in the work shed every night and could not sleep. On September 20, 2018, another large collapse occurred in the tunnel, over 20 meters long and with a volume of more than 2,000 cubic meters. It was thrilling: at that time, four or five people and machinery were still working. Team Leader Chen felt something was wrong and immediately ordered the withdrawal of machinery and personnel. They had just gotten out when everything above collapsed; two minutes later, the consequences would have been unimaginable.


On October 31, 2018, less than a year after commencement, the tunnel was finally holed through. The construction unit deployed more than 300 workers and over 20 sets of excavators and loaders, racing against time. With the coordinated efforts of the project owner and participating units, they tackled difficulties and overcame severe geological impacts such as insufficient density behind the secondary lining, numerous cavities, abnormally loose surrounding rock, and falling loose bodies at the crown. They also overcame many construction difficulties, including manually lifting and installing giant initial support steel supports, the large excavation cross-section, and the long concrete transport distance. Finally, they overcame the difficulties and completed the tunnel, laying a solid foundation for ensuring the opening of the entire Longyan section of the Xiamen-Chengdu Expressway expansion.