Two new major arteries will be added to the central area's power supply.

This article is reproduced from: Yantai Daily

Two new “major arteries” will be added to the power supply in the central districts

Zhendalu utility tunnel and Zhulin utility tunnel projects complete their main structure in June

This summer, the safety and reliability of power supply for the central urban area will be upgraded to a new level. Reporters learned on site yesterday that the Zhendalu utility tunnel and Zhulin utility tunnel projects, implemented by the Construction Service Center of the Yantai Municipal Bureau of Housing and Urban-Rural Development, are seizing the “golden period” of spring outdoor construction to accelerate progress on every step of the work. By this coming June, the two major utility tunnel projects will be officially completed, easing the power supply pressure in the central urban area. In the future, once overhead high-voltage power lines meet the conditions for underground installation and are relocated and rerouted into underground utility tunnels, situations like high-voltage lines forming a “spider web” and power towers standing densely—seen in the past—will gradually become a thing of the past, improving the living environment along the route for local residents.

The city’s longest power utility tunnel—6 work fronts all put into operation

As one of Yantai’s longest trunk-line power utility tunnels, the Zhendalu utility tunnel project, with an investment of about RMB 370 million and a total length of about 5.36 kilometers, has been “in battle” ever since entering the site in November last year—“war” is the daily routine. In the railway-parallel section of the Zhendalu utility tunnel project, when reporters look out, the utility tunnel running parallel to the railway bridges can already be clearly seen in the excavation pit, with its shape formed by concrete. Workers are tying rebar on the work fronts; with the coordinated cooperation of countless skilled hands, the tunnel’s most critical “backbone,” steadily extends westward.

“Since early spring, the weather has been dry and precipitation has been relatively low, providing plenty of windows for continuous operations. We’re accelerating each stage of work. At present, all six work fronts are fully in operation, advancing in parallel to race the clock for progress.” Zhang Wentao, project负责人 of the Construction Service Center of the Yantai Municipal Bureau of Housing and Urban-Rural Development, introduced that taking the railway-parallel section, which is currently the busiest in terms of construction and the most demanding in terms of procedures, as an example, the construction section is silt with a higher water content and loose soil. Six water pumps run 24 hours a day without interruption to pump out water, ensuring the work-front construction standards. More than 100 workers across the whole line and dozens of construction machines all moved in together. Day and night, they “run at full power,” and, according to the procedures, focus on ensuring construction progress.

As one of Laoshan District’s—and even the city’s—top-tier utility tunnel projects, the Zhendalu utility tunnel starts from the northwest corner of the intersection of Fenghuangxi Road and Zhendalu (forming a ring-network connection with the Fenghuangxi Road power utility tunnel), and heads east along the northern side green belt of Zhendalu, passing in sequence through Fenghuangxi Road, Fenghuangdong Road, Yingchun Avenue, Changning Road, Chang’an Road, Qingxiang Road, Jintan South Road, Xueyuan West Road, and others, reaching the northwest area near the Zheguzhuang interchange bridge, then turning south to cross Zhendalu, Rongwu Expressway, and Qingrong Cheng-Rail intercity railway to the southeast of the interchange bridge. What role will this “major artery,” which runs across Laoshan District and connects multiple utility tunnels into a continuous corridor, play in the future? Reporters learned that the Zhendalu power cable ducts will not only accommodate cables for the Linshan Line and Linjin Line, but will also interconnect with other utility tunnels under construction and already built at both city and district levels. While realizing the underground “collection” of cables, it will further extend the power supply radius covering the central urban area of Laoshan District, boosting capacity and enabling greater load.

Connecting power “breaks” with “inserting where there’s a gap” by the Fengxi Lake

From along the southern part of Laoshan District, driving directly to the central area, another power “artery” is also racing against time.

In the protective fencing set up within the side-access greenery strip on the north side of the Shanzhiyun residential community, pile-driving machines are stretching out their long arms to drive steel sheet piles—up to 15 meters long—into the ground. The dense arrangement of steel sheet piles at every 40 centimeters provides exceptionally strong support for the Zhulin utility tunnel project. And in the open-cut section on the east side, as excavators’ buckets swing and turn, the future space for the utility tunnel is gradually taking shape.

“The construction site of the Zhulin utility tunnel project is adjacent to the main road, Zhulin Road, and the residential area is on the south side as well, so the work front is relatively narrow. We must find a location between the road and the community where the impact on traffic and living is minimal.” Yu Zongmin, project负责人 of the Construction Service Center of the Yantai Municipal Bureau of Housing and Urban-Rural Development, explained. After weighing the options, the project department decided to construct within the greenery strip on the north side of the Shanzhiyun residential community’s side-access strip, which has not yet been opened for passage, fully without using Zhulin Road’s vehicular lanes, and to reduce interference with traffic to the greatest extent possible.

After minimizing disruption to residents’ everyday life around the area, the complex geological conditions at the site also became a “roadblock” for utility tunnel construction. Yu Zongmin told reporters that the north side of the Zhulin utility tunnel is adjacent to the Miaohou Reservoir. The subsurface characteristics are “soft on top and hard at the bottom”—the upper layer is backfill soil, and the lower layer is a solid weathered-rock stratum. Therefore, more than 3,000 steel sheet piles need to be driven in on site to ensure structural strength. Meanwhile, underground there are multiple pipelines interwoven—water supply, drainage, district heating, strong-current power, and weak-current lines—so during excavation they must be precisely avoided. Additionally, the newly built Fengxi Lake Park has already become a “check-in” spot for nearby residents to walk briskly and enjoy greenery; since early spring, visitor flow to the park has been steadily increasing. With construction adjacent to the park, controlling dust and noise is even more a top priority. To ensure the project proceeds smoothly, the construction unit invested sufficient manpower and materials, purchased and stocked materials in advance, adopted continuous uninterrupted construction, and implemented combined approaches of batch operations and cross operations to fully ensure the project is completed on schedule.

According to the construction plan, the Zhulin utility tunnel project starts from the north entrance of the Fenghuangxi Road power tunnel, follows the side-access greenery strip on the north side of Shanzhiyun, extends northward to around the梁家 utility tunnel interface. After the project is completed, the “dead ends” of the former power utility tunnels will be connected, forming a complete power transmission corridor.

Putting cables underground saves space aboveground and makes the scenery look better

Helping more high-voltage cable lines that used to run overhead “find a home,” Yantai Power’s utility tunnel construction has been continuously handing off the baton.

In October 2019, Yantai’s first dedicated power utility tunnel in the central urban area—the Liangjia Land power utility tunnel—was completed. Within the Liangjia Land area, 110kV and 220kV overhead high-voltage lines were installed into the ducts. The regional power supply reliability and power transmission capacity were comprehensively strengthened. In July 2024, the civil engineering work for the Chaoyang Station Shengli Road and Beima Road section tunnel project was officially completed. With a total investment of RMB 220 million, the tunnel project is, to date, the province’s largest in scale, longest in length, and most technically challenging curved pipe-jacking project. Not only did it carve out a通路 through complex geology along the coastal front, but it also, with a “fabric shed + minimally invasive” approach, fully reduced the impact of construction on the city’s bustling urban areas.

This summer, as the two power major arteries are built and completed in parallel, while the existing utility tunnels’ “dead-end stretches” gradually “shake hands” to connect, it is also a cost-effective economic ledger and an ecological ledger.

In recent years, with the central urban area continuing to expand capacity—especially as power load increases—building comprehensive utility tunnels and enhancing the city’s carrying capacity is undoubtedly the only path forward. However, the central urban area has complex geological conditions, high traffic volumes, and a sensitive surrounding environment. It must both ensure quality and timely completion of the projects, and reduce disturbances to surrounding areas to the minimum during construction. From the very beginning of implementing Yantai’s underground utility tunnel construction, it has charted a green, low-carbon development path of “making it more minimally invasive, more prefabricated, and more intelligent.”

“For the utility tunnel work we implement at key junction points, we don’t have to ‘tear open’ the roads. It’s like a precise ‘minimally invasive surgery.’” Zhang Wentao introduced that the project department abandoned the traditional large-scale cut-and-dig approach. In segments where conditions allow, it gives priority to non-excavation or small-excavation construction techniques such as pipe jacking, shield tunneling, and horizontal directional drilling. This greatly reduces the amount of earth excavation, transportation, and backfilling, and significantly lowers dust, noise, and solid waste emissions during the entire construction process. The whole process is carried out “quietly underground.”

In addition, the utility tunnel project promotes and uses the GRF green prefabricated foundation pit support system, replacing the traditional sprayed concrete process. The annoying problem of construction dust pollution is basically eliminated, and the support materials can also be recycled. The utility tunnel’s “sinews and bones” use high-performance composite materials, which not only extends the service life of the main structural components, but also reduces resource consumption and carbon emissions caused by major repairs later on.

With power utility tunnels put into operation, previously overhead cables are systematically collected into underground corridors, freeing up valuable aboveground and shallow underground space, and eliminating the “spider-web” visual pollution in the sky over the city. Moreover, once the utility tunnel is completed and backfilled and landscaping is done, the area’s “clean land” transfer and leasing will also have more complete development conditions, providing superior prerequisites for the project to land early and begin production early.

YMG all-media reporter Yang Jian

Correspondent Zhang Wentao Yu Zongmin Photo and report