Construction site of the Tianhu Road underground utility tunnel in Liupanshui.

On June 9, at the construction site of the eastern section of Tianhu Road in Liupanshui, Guizhou, sections of 40-centimeter-diameter water supply pipes were being slowly lowered into the underground utility tunnel through the pipe compartment. The electric pulley started, and the pipes were transferred through the tunnel, connected after splicing, and the city's new underground artery was thus built.
　　“After the connection is completed, tap water will be delivered from here to thousands of households.” Zhao Yongcheng, who was directing the pipelines into the tunnel, is a pipeline inspector with 13 years of experience at the water company. The entry of water supply pipes into the tunnel delighted him.
　　Liupanshui City is located in the Wumeng Mountain area in western Guizhou Province, with the highest altitude of 2,900.6 meters and the lowest of 586 meters, featuring typical karst landforms. There is abundant rainfall, and freezing rain occurs frequently after winter begins. After the water supply pipes enter the tunnel, inspectors only need to monitor the pipelines through surveillance, and residents' water safety is better guaranteed.
　　Building a “century project” under karst landforms
　　Going down more than 30 steps, one enters the “collective dormitory” of municipal pipelines.
　　This is an underground utility tunnel with three compartments, including a power compartment, a comprehensive compartment, and a natural gas compartment, arranged regularly and standing side by side. The middle comprehensive compartment houses heat, water supply, and reclaimed water pipelines, while the power compartment and gas pipeline are on both sides. This is one section of Liupanshui's 39.8-kilometer underground utility tunnel trunk line.
　　“Liupanshui started industrialization early and is a city brought by trains. The road ‘zipper’ and aerial ‘spider web’ phenomena are serious.” Yang Dongsheng, chief engineer of the Liupanshui Housing and Urban-Rural Development Bureau, introduced, “Liupanshui is the only western city and mountainous city among the first 10 pilot cities for underground utility tunnels in the country. The pilot can not only turn the city's shortcomings into a model but also provide reference experience for other western cities.”
　　Urban land is tight, dominated by mountains and hills, with obvious karst features, steep slopes, and abundant underground caves and underground rivers... To complete earthwork excavation and build a utility tunnel project that will last a hundred years in such an environment, construction faces huge challenges.
　　“Construction here requires, on the one hand, facing hard underground rock and repeatedly carrying out blasting; on the other hand, after blasting, one will encounter underground caves.” Chen Bo, project chief engineer, introduced that to “subdue” the caves, large volumes of stone and concrete had to be poured during construction. Sometimes, a single underground cave required 1,300 cubic meters of stone and concrete to fill.
　　Just after “subduing” the caves, soft foundations were encountered. The reporter learned that during the construction of one section of the utility tunnel, when the foundation trench was excavated to 6.2 meters underground, the construction party found that within a 200-meter range there was a soft geological layer. If a utility tunnel were built on this geological structure, the adjacent rock area would squeeze the completed utility tunnel due to different degrees of settlement, causing structural deformation. This meant that for these 200 meters, another 3 meters had to be excavated downward, and the foundation had to be replaced to meet design requirements. “Although this excavation delayed the construction period by 10 days, it can meet the quality requirements of a hundred-year test.”
　　Making the utility tunnel “smart”
　　If only the “collective dormitory” is built, the utility tunnel can only be regarded as civil engineering. “We cannot just let the pipelines move in. If the dormitory is not smart, how can we attract pipeline companies to enter the tunnel?” said Peng Jie of Liupanshui Affordable Housing Development and Investment Co., Ltd. “Only when testing, monitoring, and operation can be done by looking at a large screen can it be truly considered an underground utility tunnel.”
　　“Making the utility tunnel ‘smart’ brings the greatest benefit in safety. Gas pipelines used to be directly buried, with the pipelines deep underground and their status difficult to know. Now the gas pipelines have moved into a single room, with 24-hour intelligent monitoring, and their performance is clear at a glance.” Miao Zhanzhong, general manager of Liupanshui City Utility Tunnel Company, told the reporter that intelligent management was designed at the beginning of the utility tunnel construction.
　　Li Hailong, project manager of the First Work Area of China Construction Second Engineering Bureau, which bears the main responsibility, said: “The utility tunnel's automatic fire alarm system, as well as security, fiber-optic temperature measurement, ventilation, and other systems, all used BIM technology at the beginning of construction to establish BIM model standards. These systems can all be uniformly dispatched and controlled in the monitoring room.”
　　Among the nearly 40 kilometers of utility tunnels planned in Liupanshui, single-compartment, double-compartment, three-compartment, and four-compartment utility tunnels are built according to the actual needs of the road sections, and utility tunnels of different sizes carry different functions. In addition to centrally placing pipelines, to solve urban waterlogging, two utility tunnels containing rainwater pipelines were specially built. When rainstorms come, rainwater can be concentrated through roadside rainwater grates, flow into rainwater wells, and then the rainwater wells are connected to the utility tunnel pipelines to concentrate rainwater to designated discharge locations, greatly improving the overall flood control and flood prevention capacity of the area.
　　“From this perspective, it is not an exaggeration to call the underground utility tunnel an important infrastructure and ‘lifeline’ for ensuring urban operation.” said Yang Jian, director of the Liupanshui Housing and Urban-Rural Development Bureau.
　　PPP stirs “a pool of spring water”
　　Calculated on the basis of 100 years of operation, although the underground utility tunnel is “high quality and low price,” the one-time investment in construction cost still gives many local governments a headache.
　　As a western city, Liupanshui needs about 2.994 billion yuan to build nearly 40 kilometers of utility tunnels, while the city's fiscal revenue in 2015 was only 13 billion yuan. Taking out nearly a quarter of fiscal revenue to invest in underground utility tunnel construction is obviously unrealistic for this city. How to solve this funding problem?
　　The answer is to adopt the PPP model for construction: Liupanshui Housing Investment Company contributed 200 million yuan on behalf of the municipal government, and China State Construction Engineering Corporation contributed 800 million yuan, forming a utility tunnel SPV company. The Liupanshui Housing and Urban-Rural Development Bureau signed a PPP agreement with the utility tunnel company, granting it the concession rights for project investment, financing, construction, operation, and maintenance (the concession period is 30 years, including a 2-year construction period and a 28-year operation period).
　　In addition, there is 900 million yuan from the central government's special subsidy funds, allocated over 3 years; and the project company will finance 1.124 billion yuan from development financial institutions. Excluding the central government's special funds, all investments will be recovered during the operation period.