With the beginning and ending mileage of K5+390～K12+022.319 and the total length of 6.632km, this Project mainly includes 3 interchanges, 2 long tunnels, 1 medium bridge and 1 bridge and tunnel monitor and maintenance station. The Longding Tunnel has a length of 2,183m and the Ganggou Tunnel has a length of 1,105m, respectively ranking the second and the fifth in terms of the length of two-way eight-lane highway tunnel in the world. After completion, it will achieve the connection between south line of Jinan-Qingdao Expressway and overpass of Jinan Erhuan South Road, and Jinan-Qingdao Expressway and overpass of Jinan Erhuan East Road, and be of great significance to build a seamless urban express road network system in Jinan, ease urban traffic congestion in Jinan, and accelerate the development of the eastern urban area.

With the planned start date of August 5, 2015 and the planned completion date of December 31, 2017, this Project involves many links such as design, construction, procurement and installation, etc. The construction drawings design, construction and equipment procurement needed to be carried out at the same time, which had high requirements on the management and organizational capabilities of the Company. In addition, the contractor unit must be able to conduct the meticulous and connection of every stage, thus there was a large difficulty in organization and coordination,

The Project signed a “Scientific Research Cooperation Agreement” with Shandong University, Shandong Provincial Communications Planning and Design Institute and China University of Mining & Technology to integrate resources and give full play to the advantages of universities. Through the scientific and technological innovation activity of Super Large Cross Section Tunnel Confined Concrete Supporting Scheme, Wang Mengshu, Yang Xiumin and Ren Huiqi were invited to carry out scheme demonstrations to promote the application of the new type supporting system for tunnels and the development of full-mechanized construction of tunnels, to improve the tunnel construction efficiency, and to improve the influence of CSCEC in the industry.

For this Project, energy-gathered water pressure blasting is used for the tunnel blasting. Different from the spaced loading of the conventional smooth blasting, this new technology adopts “energy-gathered tube device” and “water bag”, places the water bag in a certain part of the blasthole, and finally uses the new loading structure backfilled with stemming. Compared with traditional blasting, the amount of explosives can be reduced by 17%, the use quantities of detonating cords can be reduced by 70%, and the blasting cost can be reduced by about 30%. Moreover, the spray formed during blasting can also contribute to dust reduction and improving the working environment.

The informational tunnel engineering construction is promoted. In view of the uncertainty and high risk of tunnel construction, this Project strengthened the construction of construction information system, implemented a video surveillance system and a personnel positioning system, and implemented visual monitoring and management of hidden construction. In the meantime, this Project established photographs and image records of concealed construction processes to ensure that the construction process is traceable and searchable.

The tunnel trunk excavation is carried out by half-step CD method instead of CD method, making the construction speed improved, temporary support saved, self-bearing capacity of the surrounding rock used fully, and being conductive to initial support quality control and saving the comprehensive cost.

The Project independently researched and developed the “construction method of tunnel collapse handled by light bubble soil + advanced large pipe shed”, successfully applied for the 2017 Shandong provincial construction method, and participated in the preparation of Shandong Provincial “Technical Specification for Application of Light Foam Soil”.

The wet spray manipulator, the new equipment, is used for tunnel concrete spraying, which is characterized by high construction efficiency (wet jet manipulator can spray at speed of up to 30 cubic meters per hour, while the speed of ordinary wet sprayers does not generally exceed 5 cubic meters per hour.), low resilience force (The concrete resilience rate of ordinary wet spray machines is generally 15%~25%, and the resilience rate of wet spray manipulator can be controlled within 10%, which reduces material consumption.), small pollution (The wet spray manipulator greatly reduces the dust density and reduces the harm to workers) and good quality (the concrete strength and compactness can be controlled easily).

Effect diagram of the entrance of the Longding Tunnel

Super Large Cross Section Tunnel Confined Concrete Supporting Scheme Demonstration Meeting

Super Large Cross Section Tunnel Supporting Site Construction Diagram

Real scene of the tunnel upon completion

Real scene of the tunnel after completion and before being open to the traffic