The whole line of the water conveyance tunnel leading from Han to Wei to the Qinling Mountains runs through the Qinling Mountains from the bottom for the first time in human history
Overcome the "Rare Difficulties in the World"
With the rotating cutterhead of a tunnel hard rock boring machine breaking the rock wall, the key control project of the Shaanxi Han-Wei-Wei Diversion Project, the Qinling Water Conveying Tunnel, was recently completed.
This is the first time in human history that the Qinling Mountains, one of the dividing lines between north and south China, have been crossed from the bottom.
Chisel the Qinling Mountains and divert clear waters.
As a national key water conservancy project, the project of diverting Han to Wei River will be completed. The water of the Han River, the largest tributary of the Yangtze River, will go north through the Qinling Mountains, and will "hand in hand" with the largest tributary of the Yellow River, the Wei River, to relieve the "thirst" in the customs and infiltrate the land of San Qin. .
By then, it can meet the domestic and industrial water consumption of 21 water recipients including Xi'an, Xianyang, Weinan and other cities, benefiting more than 14 million people.
So, what is the origin of the Han-Ji-Wei project, and how was it constructed?
How difficult is it to cross the Qinling Mountains?
How did the many worldwide problems encountered in the construction process be overcome one by one?
1 "Adjusting" water and "quenching thirst" Guanzhong in southern Shaanxi, the project of diverting Han to Wei River is a huge project
The average annual water transfer scale can reach 1.5 billion cubic meters, which can meet the water consumption of 21 water recipients such as Xi'an and Xianyang, benefiting more than 14 million people
The old man Kou Zongwu, who had a special affection for water, was very excited when he learned that the Qinling Water Conveyance Tunnel was completed.
"It's not easy to get through this after about 10 years," said Kou Zongwu, who is 82 years old this year and once served as director of the Shaanxi Provincial Water Resources Management Office.
Water is the source of life.
Shaanxi straddles the two major river basins of the Yellow River and the Yangtze River, but the distribution of water resources is extremely uneven.
The southern Shaanxi region south of the Qinling Mountains has abundant water resources, accounting for more than 70% of the total water resources in the province.
The Guanzhong and Shaanxi regions to the north of the Qinling Mountains have many key cities and important factories along the route and are densely populated, but water resources are scarce, accounting for only nearly 30% of the province's total water resources.
In the 1980s and 1990s, the water shortage problem in Shaanxi became more and more serious.
Water supply at different times, every household's faucets are "locked"... The "water shortage" in summer has become an indelible memory for many people in Guanzhong.
"As long as it rains, everyone collects rainwater and stores it in various ways. My father often takes me to find water far away from home." Mr. Xiao, who was born in Pucheng County, Weinan City, Shaanxi Province in 1980, told reporters, He still remembers the experience of "searching for water" as a child.
It is imminent to solve the problem of "water crisis" in Shaanxi.
The concept of "adjusting" water and "quenching thirst" in Guanzhong started from the abundant water resources in southern Shaanxi.
After multiple investigations, demonstrations and reports for approval, the Han-to-Wei River project, known as the Shaanxi version of the "South-to-North Water Diversion" project, was implemented in 2012.
The reporter learned that the project is divided into two parts: water transfer and water distribution.
Among them, the water transfer project consists of three parts: the Jinjinxia Water Control Project, the Sanhekou Water Control Project and the Qinling Water Transmission Tunnel; the water transmission and distribution project consists of the Huangchigou Water Distribution Project, the north-south trunk line and 23 branch lines.
According to the design, under the adjustment and coordination of the two major water conservancy hubs, Jinjinxia and Sanhekou, the water of the Han River will pass through the Qinling Mountains through a 98.3-kilometer water transmission tunnel, and then be optimally allocated to Guanzhong and northern Shaanxi through the water transmission and distribution project.
Located 2 kilometers downstream of Jinjinxia Guotan in Yangxian County, Hanzhong City, Shaanxi Province, the main stream of the Han River is the Jinjinxia Water Conservancy Project.
This is the leading water source project to divert Han to Wei.
"The annual water supply scale can reach 1 billion cubic meters, and the design lift is 106.45 meters." Ren Haiping, deputy secretary of the Party Committee and executive general manager of the Second Engineering Company of China Water Resources and Hydropower Twelfth Engineering Bureau Co., Ltd., and the project leader of the Golden Gorge Water Control Project, told reporters , this water conservancy project has the first pumping station in Asia, "the 7 pumping units behind the dam pump the water 106.45 meters high with a pumping flow of 70 cubic meters per second, and then send it downstream into the water transport tunnel. . It is expected to achieve water storage by the end of this year.”
Sanhekou Water Control Project, about 17 kilometers away from Jinjinxia Water Control Project, is the adjustment center of the entire water transfer project, and can achieve 500 million cubic meters of artesian water supply every year.
"At present, the concrete pouring of the main structure of the Huangchigou water distribution hub at the exit of the Qinling Water Transmission Tunnel has begun, and it is expected to supply water to Xi'an in the early stage this year." China Power Construction Group Northwest Survey and Design Research Institute Co., Ltd., the second phase of the Han-Jiwei project Li Yujie, chief design engineer of the overall survey and design coordination project department, told reporters that the water transmission and distribution project mainly supplies water to the water-receiving water plants through the buried pipelines or tunnels of the main and branch water transmission projects.
After the completion of the Han-to-Weihe project, the average annual water transfer scale will reach 1.5 billion cubic meters, benefiting 4 key cities of Xi'an, Xianyang, Weinan and Yangling, as well as 11 county towns, 5 new cities and 1 industry along the banks of the Weihe River. The park, with more than 14 million people, can effectively change the situation of over-exploitation of groundwater and squeeze ecological water in Guanzhong area, improve the carrying capacity of water resources, and restore the ecology of Weihe River.
2 Rock burst water inflow, fault collapse, the difficulty of comprehensive construction is rare in the world
"Almost all the problems of tunnel construction in the world can be met here." Construction workers must wear steel helmets and bulletproof vests when working
The geological conditions of the Qinling Mountains are extremely complex, and the difficulty of crossing from the bottom is unprecedented.
As a key control project of the Han-to-Wei River diversion project, the Qinling Water Conveying Tunnel is 98.3 kilometers long and 1300 to 2012 meters deep.
Among them, over 30 kilometers across the main ridge of the Qinling Mountains (cross-ridge section), due to the complex geological structure, it is divided into the southern part of the Lingling and the northern part of the Lingling.
According to reports, the entire water conveyance tunnel passes through 3 large regional faults, 4 secondary faults and 33 general faults, involving more than 20 types of lithology.
Faced with the surrounding rock with a quartz content of 96% and a compressive strength of more than 300 MPa, even TBM, known as the "king of roadheaders", is somewhat "overwhelmed".
"The cutter head is like excavating on a 'steel plate', and sometimes it takes three or four hours to excavate 1 meter." According to the introduction of the relevant staff, the super-hard rock causes a huge amount of wear on the TBM cutter head, and at least tens of thousands of cutter heads are damaged.
In addition, the construction process also faced a series of technical problems such as high temperature and high humidity, long distance, large burial depth, high frequency and strong rock burst, and inrush water. "Almost all the problems of tunnel construction in the world can be met here." Foreign experts commented that "the difficulty of comprehensive construction is rare in the world".
"It is very surprising that all these geological disasters are completely covered, and they are all very serious." said Chen Zuyu, an academician of the Chinese Academy of Sciences and an expert in water conservancy and hydropower civil engineering.
"The most uncomfortable thing is the high-temperature and high-humidity working environment." Song Wei, project manager of the China Railway 18th Bureau's Han-Ji-Wei project, introduced that the temperature of the working surface in the tunnel is around 40°C all year round, and the relative humidity is as high as 90°C. %.
In the words of the workers, "it's like taking a sauna, you will sweat profusely when you don't move".
"I have to drink five or six catties of water in each class," said Wu Zongqing, deputy chief engineer of electromechanical engineering of the Hanji-Wei Project Department of China Railway Tunnel Group.
What impressed Wu Zongqing deeply was the huge water gushing that occurred on the face (ie, the working face) of the Lingnan TBM construction in February 2016.
"The groundwater is like a high-pressure water gun, and the daily water inflow is as high as 46,000 cubic meters, which is 3.76 times the maximum water inflow of the entire designed tunnel. Most of the TBM's body is submerged and unable to move." According to Wu Zongqing's recollection, more than 2,000 people participated at that time. Pumping water for emergency rescue can avoid damage to the entire equipment circuit.
Since then, how to efficiently solve the problem of pumping water in the reverse slope tunnel with the longest inclined shaft in Asia at 5,820 meters has become the focus of Wu Zongqing and his apprentices.
In the end, they successfully developed pumping automation equipment.
Rock burst is also a "stumbling block" in the construction process.
Recalling the frequent rock bursts, Yang Zhonglun, the leader of the excavation team of Lingnan TBM, still has lingering fears: "It's like a bomb. I remember the strongest one, the rock was ejected more than 20 meters."
Therefore, in addition to requiring construction personnel to wear steel helmets and bulletproof vests when working, construction managers have also carried out a series of scientific researches with relevant scientific research forces, and innovatively adopted geological advance prediction techniques such as induced polarization method and three-dimensional seismic wave method. , to minimize the risk of disasters such as rock bursts, landslides, water inrush, and harmful gases.
According to reports, the accuracy rate of rockburst prediction and early warning focusing on microseismic monitoring is as high as 85%.
Monitoring found that since the construction of the Qinling Water Transmission Tunnel, more than 4,000 rock bursts have occurred, with a maximum magnitude of 1.6, but there has never been a general or above safety accident.
Underwater robots with functions such as unmanned inspection and autonomous navigation, creating a world record for ultra-long-distance construction ventilation... With the help of science and technology, one construction problem has been overcome.
3 Wastewater purification, "Sky Eye" monitoring, to protect the clear waters and green mountains of Qinling Mountains
The fish pass across the dam is to ensure smooth migration and spawning of fish, while the fish multiplication station is for "seedling and breeding" for water biodiversity in the Han River Basin.
The implementation of the Han to Wei project must pass through the natural barrier of the Qinling Mountains.
Compared with bypassing the Qinling Mountains, crossing from the bottom of the Qinling Mountains is the shortest and least expensive engineering construction plan, and the impact on the natural environment of the Qinling Mountains is also small.
According to the engineers who participated in and presided over the planning and design of the Han-Ji-Wei project, the current plan was selected from nearly 10 routes inspected by the expert group that year.
The project of diverting the Han to the Wei River passes through many national and provincial nature reserves such as Crested Ibis, Tianhua Mountain, and Heihe. In addition to comprehensively considering economic factors, the planning, design and construction are also important for the ecological protection of the Qinling Mountains.
The design of the dam-crossing fish passages and fish breeding stations of the Golden Gorge Water Control Project is based on ecological protection considerations.
According to industry insiders, the integrity of the fish biological chain affects the ecological balance.
The fish pass across the dam is to ensure smooth migration and spawning of fish, while the fish breeding station is to "cultivate seedlings and breed" for the water biodiversity in the Han River Basin.
In September last year, the Han-Ji Weisanhekou Reservoir held the first fish proliferation and release activity. 7 species and 175,000 fry were bred and cultivated by the Jinjinxia Fish Breeding Station.
During the construction process, the construction manager took concrete actions to protect the clear waters and lush mountains of Qinling Mountains.
It is understood that in the process of tunnel construction, a large amount of waste water and waste residue will be produced.
For wastewater, construction managers build large-scale water quality "purifiers" at the exits of each tunnel. Through the process of "high-efficiency sedimentation tank + filter tank + activated carbon treatment", the wastewater is deeply purified, and the purified water can reach the surface water quality standard of Class II.
"Basically, it has reached our drinking water standard." Zhao Xuegong, head of the Heihe Water Source Environmental Protection Management Station in Xi'an, said in an interview.
At the same time, combined with the regional geographical environment, a slag yard is built in a place far from the protected area for stacking waste slag.
After the slag yard is used up, it will be reclaimed and converted into farmland.
At present, a total of 370 mu of high-standard farmland has been built.
At the construction site and the entrance of the tunnel, there are "eyes of the sky".
"Through mobile phones and computers, the implementation of environmental protection measures at the construction site can be viewed remotely and dynamically in real time."
Not only that, the Crested Ibis UAV Squadron also goes deep into the work area from time to time, and conducts surprise inspections on the implementation of environmental protection measures by means of high-altitude drone photography, river water collection, and on-site analysis by spectrum analyzers.
Our reporter Wang Zhen