"When the project was tendered, the data showed that the geology was dominated by three types of rocks. After the construction, it was discovered that the four types of surrounding rocks accounted for more than 50%, and the rocks were broken and turned into mud when exposed to water. Our TBM is a hard rock tunneling machine. , It’s like a horse stuck in a quagmire, unable to exert energy”, said Chen Lixin, the deputy project manager of the Shiyan Water Supply Project Department.

The Shiyan City Center Water Resources Allocation Project is a livelihood project that the people of Shiyan City have been looking forward to for many years, and it is also a pioneering project for the company to intensively cultivate the Hubei market. The project uses Pankou Reservoir as the water source, and supplements ecological water to the urban area through the newly built Pankou Reservoir to Majiahe Reservoir diversion main line, and the new Majiahe Reservoir to Baier River Reservoir diversion branch line.

According to the data, the main construction tasks of the third tender section undertaken by SINOHYDRO BUREAU 3 CO., LTD No. 4 Engineering Company include the 947.1-meter Jundi River inverted siphon, the 195-meter Jundi River culvert and the No. 5 tunnel. Among them, Tunnel No. 5 has a total length of 13.7 kilometers and is mainly constructed with an open TBM with a diameter of 4.03 meters.

Sun Lanbin, deputy project manager, said that during the epidemic, when the assembly personnel were insufficient and the equipment was not on-site in time, the project department carefully organized and planned carefully, and successfully completed the assembly task of the TBM host in 45 days.

The reporter learned that since the start of construction, the project department has realized the start of the project on December 18, 2020 and the start of TBM excavation on September 28, 2021. Two nodes. As of February 17, the TBM of hole 5 has excavated 5.2 kilometers.

Since the start of the project, it has encountered difficulties such as land acquisition and resettlement, landslides and water gushing. Chen Lixin said: "Since entering the site, the land acquisition problem of the Jundi River inverted siphon has not been resolved for a long time, resulting in the failure to start construction of the Jundi River inverted siphon as originally planned." In response to this problem, the project department quickly established a good cooperative relationship with the local government through the coordination of the owner, and acted as a "middleman" between the owner and the local government to speed up the progress of land acquisition. Since the inverted siphon occupies a long line and involves many villagers, the land acquisition problem cannot be completely solved at the same time. The construction strategy of "requisitioning one piece and dry one piece" is adopted. The exit section of the inverted siphon will officially start construction in October 2021.

Due to the harsh geological conditions, landslides and water gushes of different scales have occurred frequently in the cave since TBM excavation. On March 9, 2022, a geological landslide occurred in Tunnel No. 5, with a maximum depth of 4.5 meters. The combatants overcame difficulties such as the inability to close the loop of the arch frame, the narrow space under the main girder for slag removal, and the soft rock support shoes that could not be tightened tightly. And a series of measures, through 16 days of treatment, passed the bad geological section smoothly.

Wang Deshan, deputy production manager of the project, especially emphasized the difficulty of constructing small-diameter tunnels. The space is small, the air flow is not smooth, and personnel have to bend over when walking on the working surface. When the equipment is excavated, the noise and smoke are particularly loud. The reporter and his team took pictures in the cave and actually experienced it once. Because there are too many leaks in the cave, and most of them are rock cracked stream water, it is quite troublesome to deal with, so the water depth is as high as 0.5 meters in some places. To get to the cutter head, you have to go through the connecting bridge and the main beam, and you need to wade to get there.

Wang Yong, the safety director of the project department, said that since the construction, there have been 23 sudden water gushes of varying degrees, which seriously affected the construction progress. The project department has successfully passed through the water gushing tunnel section by adding emergency drainage pumps and chemical grouting to block water and other measures.

Due to the small diameter of the tunnel, many functions of the TBM equipment cannot be used. To put it bluntly, the equipment is defective. We have successively carried out 5 equipment transformations on the ventilation equipment, slag extraction equipment, and bolting rigs to adapt the equipment to small-diameter tunnels. construction environment. At present, there are still some equipment defects that are being improved, which is also the focus of our work. Through the improvement of equipment, normal excavation can be realized.

Sun Shuang, chief engineer of the project department, said: In addition to the difficulties caused by geological conditions, the contract conditions of the project have changed greatly compared with the bidding stage, which has led to operational risks in the current project. Taking rock strength as an example, the settlement deviation was 16.17 million yuan due to the discrepancy with the bidding stage. In addition, the backfill concrete of the starting tunnel, the retaining wall of No. 8 Road, and the first and second phases of the Jundi River inverted siphon cofferdam were all optimized and cancelled, resulting in a reduction of 23.65 million yuan in the contract value.

The project also faces the problem of TBM brain drain. Chen Lixin said that the project department will increase the intensity of talent training this year, recruit new recruits from colleges and universities, adopt the form of "teacher leading apprentices", and "one-to-one" training based on the position, so as to make up for shortcomings as soon as possible.

The reporter learned that in the face of many difficulties, the project department has achieved certain results. In the TBM assembly stage, it overcame the impact of the epidemic and completed the equipment assembly 15 days ahead of schedule. On September 28, 2021, TBM began excavation and met the contract requirements, and the owner sent a congratulatory letter to praise it.Editor/Ma Xue