On June 28, the reporter learned from the Haikou Underground Utility Tunnel Company of China Railway Fourth Bureau that recently, the 2016 national utility tunnel pilot city performance assessment, jointly conducted by the Ministry of Housing and Urban-Rural Development and the Ministry of Finance, was released. Haikou's underground utility tunnel pilot work scored a high 91 points, entering the excellent category and receiving “praise” from national assessment experts.
At the Haikou underground utility tunnel prefabrication plant, the reporter saw a new construction technique. By applying this new technique, construction costs are reduced, and utility tunnel construction is expected to speed up by at least 20%.
“We combined Haikou's actual geographical and hydrological conditions, and while drawing on advanced experience at home and abroad, explored and applied an upgraded double-skin wall prefabricated assembly utility tunnel construction method.” said Ding Changming, a person in charge of the prefabrication plant. They will scientifically divide the utility tunnel structure into components such as outer walls, intermediate partition walls, and roof slabs according to its structural characteristics, carry out standardized design and production in the factory, install them on site using cranes and other equipment, and form an integrated whole through post-cast self-compacting concrete.
The U-shaped shield technique, expected to shorten the construction period by 30%, is also a new technique in the Haikou utility tunnel pilot. According to Li Guo, head of the Third Project Management Department of Haikou Underground Utility Tunnel, the U-shaped shield is a new mobile support device suitable for underground utility tunnel construction with a cover depth of less than 2.5 meters. It consists of telescopic guard plates, telescopic cylinders, front, middle, and rear shield bodies, and pushing cylinders. The U-shaped shield can achieve automated, intelligent, and remote-controlled information-based operations in actions such as advancing, soil removal, and lining assembly. Compared with ordinary open-cut sequential construction, it can reduce labor by 50%, save costs by 40%, and shorten the construction period by 30%.
The person in charge stated that currently, due to foreign technological monopoly, there is no precedent for its application in underground utility tunnel construction. This project independently developed it, filling the gap in the domestic application of U-shaped shields in utility tunnel construction.
At the construction site of the Yehai Avenue underground utility tunnel, the reporter saw that at a depth of 11 meters underground, on a 10-meter-wide working face, the contractor had set up a double-layer four-compartment structure. According to reports, the project adopted a design using the central green belt to create a “double-layer four-compartment cross-section,” which solves the problem of insufficient working space while meeting the needs of pipelines along the route. It is the country's first “double-layer four-compartment” utility tunnel.
It is understood that since the launch of the Haikou pilot, the underground utility tunnel has continued to undergo technological innovation. Multiple new techniques such as double-layer four-compartment, U-shaped shield, and double-skin wall prefabricated assembly construction lead the country. The utility tunnel pilot project has received national “praise” and has been listed as a national third-batch PPP demonstration project; it also took the lead in realizing the country's first gas pipeline entry into a utility tunnel, providing replicable and scalable demonstration experience for the whole country and winning praise from experts of the China City Gas Association.
According to reports, Haikou has established a utility tunnel construction and operation model centered on the Public-Private Partnership (PPP) model, with the joint participation of social capital and pipeline units. The government side strengthens on-site supervision through supervision engineers and entrusts a third party to conduct full-process tracking audits to ensure standardized processes. In less than two years, a total investment of 3.043 billion yuan has been completed, and 23.88 kilometers of tunnel bodies have been built. All 23 utility tunnels with a total length of 43.24 kilometers included in the pilot plan have started construction, and seven types of pipelines including electricity, communications, gas, water supply, and sewage are gradually being incorporated into the tunnels. All are expected to be completed by August next year.