The Xi'an Underground Utility Tunnel project, currently one of China’s largest infrastructure projects, completed the key Kunming Road tunnel section in May 2019 in a first phase of construction. PENTRON ADMIX ensured that the complex underground design would remain waterproof and durable during its projected 100-year life cycle.
Often called the birthplace of Chinese civilization, Xi'an is one of the country’s most popular tourist destinations. Situated at the eastern end of the famous Silk Road and once the capital city of numerous imperial Chinese dynasties, today’s Xi’an is the capital city of the Chinese province of Shaanxi. The Xi'an–Xianyang metropolitan area has a population of 12.9 million and is the most populous city in Northwest China.
“Most people in the West know Xi’an through the Terracotta Warriors, a 2,000-year-old army of clay statues that guarded the tomb of China's first emperor,” explains Jozef Van Beeck, Director of International Sales & Marketing for The Penetron Group. “The city is a must see for any visitor to China – and today it’s an important industrial and educational center for the whole region.”
Construction on the Xi’an utility tunnel project is ongoing. With estimated total costs of US$2.6 billion, it is currently China’s single largest infrastructure project. The planned 145.5-km (90-miles) of tunnel encompasses a main tunnel and numerous branch tunnels that connect the capital city with the adjacent Lantian and Huyi counties and the Yanliang and Lintong districts.
“There are many more superlatives beyond the sheer cost and scope of the Xi’an project,” states Jozef Van Beeck. “For example, with its different levels for rainwater, electrical, gas and access tunnels, it is the most comprehensive tunnel design, as well as the longest total tunnel mileage project, ever undertaken in China.”
Among the superlatives is the design of the Xi 'an underground utility tunnel, a two-layer/five-tunnel design that combines two rainwater tunnels on top of three tunnels of electrical, gas and general connections. The Xi’an tunnel project has a specified 100-year design life and Level I waterproofing grade. *
“The project specifications placed high demands on any concrete waterproofing solution considered by the planners,” adds Jozef Van Beeck. “Penetron China was called in to advise the project engineers on how to best achieve the desired performance parameters.”
The recently completed Kunming Road tunnel section is a crucial part of the entire project: a main tunnel that crosses over three subway stations, seven subway tunnels, and a difficult geologic zone. The base of this tunnel section – at 12-17 m (40-56-feet) underground – is at the same level as the city’s Dahuan River, where the underground water level fluctuates seasonally from – 5-16 m (16-53-feet) below the surface.
PENETRON ADMIX was used for the concrete structure of the three bottom tunnels exposed to the constant – and fluctuating – hydrostatic pressure deep underground. Not only did PENETRON ADMIX crystalline admixture meet the Level I waterproofing grade and 100-year durability standards, the Kunming Road section was also completed before the allotted deadline, thanks to a much simpler construction method when compared to the installation process for a membrane solution.
PENETRON ADMIX is easily added during batching, forming part of the concrete mix and hardened matrix from day one throughout the life of the concrete. The permeability of the PENETRON ADMIX-treated concrete is lowered as the crystalline network is formed by the self-healing and sealing process activated through water exposure.
“Once the Xi’an tunnels are in place, it will mark the end of a history of inland inundation of surrounding areas. This project will eliminate the chronic drainage problems of Xi’an’s southern suburbs and the surrounding low-lying areas,” concludes Jozef Van Beeck.
* The Level I waterproofing grade in China designates that the concrete structure has no moisture penetration and the surface has no seepage (wet/damp spots).