184 days in advance, the first long-distance tunnel over 10 kilometers in Yunnan Dianzhong Water Diversion Project will be connected to the tunnel | Project | Water Diversion
On August 9th, after 1350 days of intense construction, the 11.2 kilometer long Longqing Tunnel of Yunnan Dianzhong Water Diversion Project was completed 184 days ahead of the planned schedule. This is the first extra long tunnel with a length of more than 10 kilometers that has been fully connected along the entire line. Its construction unit, China Railway First Bureau, has also become the first unit in the 40 main sections of the Dianzhong Water Diversion Phase I project to fully connect the tunnel construction.
The Dianzhong Water Diversion Project faces "six world-class challenges" in the construction process and needs to overcome "ten world-class technical difficulties". It is a truly "living" geological museum.
![184 days in advance, the first long-distance tunnel over 10 kilometers in Yunnan Dianzhong Water Diversion Project will be connected to the tunnel | Project | Water Diversion](https://a5qu.com/upload/images/1706b08eda504e11734299d86dec728d.jpg)
Project leader Duan Liangjun introduced: "The Longqing Tunnel is a microcosm of this' Geological Museum '. During the construction process, 8 large karst caves and more than 200 small karst caves were excavated and exposed, as well as 12 collapses and sudden mud and water surges. Among them, the daily average seepage volume of the upstream and downstream main tunnels of the Longqing Tunnel No. 1 branch is as high as 20000 cubic meters, and the daily sudden mud and water surges at the intersection of the Longqing Tunnel No. 2 branch reach 12000 cubic meters. The total length of the tunnel's soft rock deformation section is 830 meters. Among them, the maximum deformation of the first level fault in Xijian Village downstream of the Longqing Tunnel No. 1 branch is 60 centimeters. We have taken targeted construction measures according to different geological conditions, following the principle of' exploration before excavation '." The construction will be carried out in accordance with the principles of strengthening water blocking, combining water blocking and drainage, limited discharge, graded treatment, and highlighting key points. The completion of the Longqing Tunnel is also the first tunnel in Yunnan Province's Yunnan Central Water Diversion Phase I Project, with a total length of 664 kilometers and more than 40 sections, to achieve comprehensive completion. "
In addition, "soft rock deformation" is also a major "pain point" faced by the construction of the Longqing Tunnel. The common saying in underground tunnel excavation is' bully the hard and fear the soft '. Once encountering soft rock deformation, it is like dancing on tofu blocks. When encountering groundwater again, the muddy sandstone shale is like a' swamp '. We usually have a' water curtain hole 'on our head and a' swamp 'on our feet. To solve the problem of soft rock deformation, we first reserve the deformation amount based on previous construction experience, and each time consider the number of steel support processing according to the length of 5 to 10 meters, to prevent frequent changes in soft rock. The reserved deformation amount of steel support is too large or too small to cause cost waste. Then, we ensure timely' sealing into a loop ', and make predictions based on geological forecasts, advanced horizontal exploration holes, and actual conditions of the surrounding rock, so as to make judgments first and then determine the plan. The most crucial thing is that we make decisions based on "The soft rock tunnel section adopts an excavation method mainly consisting of three steps and four steps, and the support adopts a combination of advanced large pipe shed, steel support, self-propelled locking foot pipe shed, anchor spraying, horizontal transverse support, and radial consolidation grouting. In the end, this problem is well overcome," said technical leader Dou Ziqi in detail.
![184 days in advance, the first long-distance tunnel over 10 kilometers in Yunnan Dianzhong Water Diversion Project will be connected to the tunnel | Project | Water Diversion](https://a5qu.com/upload/images/5d2143a9f511fb68cf618d0a531cf134.jpg)
The Dianzhong Water Diversion Project is a landmark project among the 172 major water conservancy projects for water-saving and water supply determined by the State Council. It is also the largest and most invested water resource allocation project in Southwest China. The engineering design takes water from the Jinsha River, about 1.5 kilometers upstream of Shigu Town in Lijiang City, and the pump station lifts the water to the main canal. Then, the water transmission project starts from Shigu Town for self flow water transmission, passing through Lijiang City, Dali Prefecture, Chuxiong Prefecture, Kunming City, Yuxi City, and ending at Honghe Prefecture. The total length of the water transmission line is about 664 kilometers. After completion, 3.4 billion cubic meters of high-quality water can be diverted annually to the central region of Yunnan, alleviating the contradiction of urban production and domestic water use, improving the ecological and water environment of rivers and lakes in the region, and benefiting a land area of 37000 square kilometers and more than 11 million people.