First Phase of the North Main Canal of the Xiangjiaba Irrigation District

The first phase of the North Main Canal of the Xiangjiaba Irrigation District is one of the 172 key water conservancy projects determined by the State Council. Upon completion, the irrigation area will reach 1,985,700 mu, completely solving the problem of water for production and domestic use in the water-scarce areas of the four cities in southern Sichuan. It is known as the “Dujiangyan” of southern Sichuan. The first phase is implemented in two steps; currently under construction is the first step, which started in December 2018 and is scheduled to achieve water flow in August 2024.

On-site Progress

In early spring, southern Sichuan welcomes consecutive sunny days, which is a good time to advance the construction. Recently, at the construction site of the Longdongyan Tunnel Project of the Xiangjiaba Irrigation District in Yibin City, we learned that walking through the construction adit into the huge tunnel with an excavation diameter of 9.9 meters, a cold wind blows, contrasting with the rising temperature outside.

“As of now, 96.5% of the total length of the 9,951-meter Longdongyan Tunnel has been excavated, and concrete lining construction is being intensified on the excavated sections.” At the beginning of the new year, Yang Wenqing, Party branch secretary of the Longdongyan Tunnel Project Department of Sinohydro Bureau 6, has been “soaking” on the site all day to ensure the schedule and construction quality.

Due to the long construction period, the Longdongyan Tunnel Project was once an important controlling node of the first step of the first phase of the North Main Canal of the Xiangjiaba Irrigation District. The smooth progress of the tunnel construction has laid a solid foundation for the project to achieve water flow on schedule.

Breaking Down into Small Goals
Full-scale construction, increasing work faces to ensure progress

“The average monthly advance per work face reaches 230 meters; our excavation speed in similar rock formations is leading domestically and even internationally.” Yang Wenqing introduced that southern Sichuan is mostly characterized by shallow hilly terrain, and the underground rocks are mainly low-hardness rocks such as sandstone and mudstone. The construction personnel use the traditional drill-and-blast method for tunnel excavation, drilling holes in the rock wall, placing explosives, blasting, and clearing debris to carve out a huge space nearly 10 meters in diameter.

Does low rock hardness make excavation easier? In response to the reporter's question, Wu Chong, quality director of the Longdongyan Tunnel Project Department, explained that low rock hardness is equivalent to drilling a hole in mud; the bearing capacity of the rock mass is insufficient, so reinforcement measures must be taken after each excavation section, naturally increasing the construction difficulty and time.

The surface of southern Sichuan is dotted with ponds and rivers of various sizes, and the tunnel especially needs to pass under many residential houses, expressways, and railways, which further increases the construction difficulty. Liu Xiangjun, deputy chief engineer of Sichuan Xiangjiaba Irrigation District Company, introduced that they will optimize and adjust the design plan through multi-faceted comparison and selection. The first phase of the North Main Canal is implemented in two steps; the first step under construction is 146.49 kilometers long with more than 80 work faces. This year, 110 new work faces are planned to be started.

“By continuously increasing work faces, we break the overall project into small goals, and through collaborative cooperation, complete all construction tasks with quality and quantity guaranteed.” Luo Guoshu, chairman of Xiangjiaba Irrigation District Company, stated that currently all 7 bid sections of the first step have started construction. The project has reversed the annual schedule, breaking down the plan into months, refining it into weeks, and implementing it on a daily basis. By ensuring the week with the day and the month with the week, the annual target tasks are ensured to be completed.

Collaboration for Synergy
Joint meetings resolve construction difficulties

Unfolding the overall layout map of the first phase of the North Main Canal of the Xiangjiaba Irrigation District, the main canal and its branch canals and sub-branch canals marked with thick red lines spread across the map like a “giant dragon” winding through the land of southern Sichuan. Among them, the longest branch canal—the Qiuchang Branch Canal—extends all the way north into the Yantan District of Zigong City.

“Zigong is one of the 50 cities in China with severe water shortages. The construction of the project will help the local area fundamentally break the water resource bottleneck.” At the construction site of the Zigong section of the Qiuchang Branch Canal, Zhao Huarong, executive deputy manager of the project department of Sinohydro Bureau 14, was guiding the construction.

After the project started, the biggest difficulties were concentrated in land acquisition and resettlement work. On September 14 last year, the governments of Yibin, Zigong, Neijiang, and Luzhou held the first meeting of the coordination and promotion leading group for the construction of the first step of the first phase of the North Main Canal of the Xiangjiaba Irrigation District to discuss and resolve issues such as land acquisition, resettlement, and relocation of poles and pipelines during the project advancement. After the meeting, the water conservancy departments of the four cities established a supervision and guidance mechanism, with principal leaders and responsible leaders going to the project site for inspection and guidance every week. The leaders in charge of Xiangjiaba Irrigation District Company are stationed at the bid sections for a long time; small problems are solved on-site without delay overnight, and major problems are coordinated and resolved early. A liaison mechanism has been established with the local governments and relevant departments where the project is located to maximize the acceleration of project construction. Zhao Huarong said, “After the joint meeting, work efficiency has greatly improved. In less than a week, the Zigong section handed over 24 parcels of land, promoting the smooth progress of the project.”

At present, the joint meeting of the four cities in southern Sichuan has formed a mechanism and will be held again soon to focus on resolving related issues during the project construction process.

●Thirty-Six Strategies for Project Construction
Ensuring Quality

In response to construction difficulties, special plans are formulated. Based on project progress, expert demonstrations and consultations are actively carried out, and construction exchanges and evaluations are organized among bid sections to learn from each other's strengths and improve the construction level.

To address the construction safety of shallow burial and intersection sections of the tunnel, the construction party adjusted the drill-and-blast method to non-blasting excavation methods such as cantilever roadheaders and milling excavators.

Promoting Progress

Fully mobilize the enthusiasm and initiative of all participating parties, organize and carry out the “100 Days of Hard Work · Five Comparisons and Five Competitions” labor competition, stimulate the work enthusiasm of the construction personnel, and form a good construction atmosphere of comparing, learning, catching up, helping, and surpassing.

According to the annual production target tasks and combined with the current project progress, the annual schedule is reversed, and the construction plan is broken down into months, refined into weeks, and implemented on a daily basis, ensuring the week with the day, the month with the week, and the year with the month.