At the site of the secondary lining reinforcement binding in the tunnel, workers cooperate to ensure the quality of the reinforcement binding.

　　Under the Pingfang Bridge on the East 5th Ring Road, traffic is heavy and noisy as usual; little do people know that more than 20 meters below the bridge lies a true "giant dragon"—the East Main Canal of the South-to-North Water Diversion Project. At the East Main Canal construction site, a shield tunneling machine with a diameter of six meters is advancing day and night; with only more than 200 meters to go, the cutterhead of the shield machine will "break through" and the entire water transmission ring will be fully connected.

　　It is expected that by the end of this month, a water transmission "giant dragon" about 107.3 kilometers long will officially straighten its "backbone," winding its way beneath the ring road formed by the North 5th Ring Road, East 5th Ring Road, South 5th Ring Road, and West 4th Ring Road...

　　Visit

　　Descending more than 200 steps

　　As if entering a "time tunnel"

　　The reporter walked into the ongoing construction of Section 8 of the East Main Canal of the South-to-North Water Diversion Project. The working shaft is located directly below the southeast corner of Yuantong Bridge; traffic on and under the East 5th Ring Road flows normally, and without the reminder of the construction fencing, one would hardly notice that construction work is underway here.

　　The working shaft is more than 20 meters deep. After descending more than 200 steps in one go, the reporter's calves felt tight, but Chen Yonghong, deputy manager of the East Main Canal Construction Section 8 Project Department who accompanied the reporter, was not even out of breath and went straight down to the bottom—the shield launching and receiving shaft. "I run back and forth every day and am used to it; at most, I go up and down six or seven times a day." Chen Yonghong walks fast and talks fast. The entire East Main Canal project is proceeding simultaneously, and all sections are competing to catch up and surpass. The reporter ignored the mud and quickened his pace to follow.

　　A "giant" suddenly appeared before the eyes. "This is a shield tunneling machine with a diameter of 6 meters; it is what bores holes underground. It just broke through a couple of days ago." The shield machine, having completed its task, was covered in mud and looked somewhat "exhausted." Several workers were "washing" it, and in a few days it would be lifted out of the working shaft.

　　Stepping on a temporarily built simple ladder, the reporter followed Chen Yonghong through a gap into the heart of the shield machine. During excavation, the cutterhead rotates to cut the soil ahead, and the conveyor belt immediately transports the soil to the rear and up to the surface. Then, the operator uses a remote control to direct the segment erector behind the cutterhead to assemble six shield segments, each 1.2 meters wide and 30 centimeters thick, into a ring. It advances 1.2 meters in 20 minutes, and then another 20 minutes to assemble a ring.

　　The entire 44.7-kilometer East Main Canal is assembled ring by ring in this way, forming a winding tunnel. For construction convenience, lighting is installed along the inner wall of the tunnel. Under the light, the shield rings form halos extending into the distance, the halos growing smaller and farther away, like a "time tunnel."

　　"The place where you are standing will be full of water from the Danjiangkou Reservoir after this year's flood season," Chen Yonghong brought the reporter's thoughts back. The reporter almost forgot that this large tunnel with an outer diameter of 6 meters is not some "time tunnel" but the main water transmission pipeline of the South-to-North Water Diversion Project in Beijing.

     37 high-risk sources in the East Main Canal

　　35 have been successfully crossed so far

　　Taking off his safety helmet, the reporter discovered that Chen Yonghong was bald. "Being bald is most convenient on a construction site." Chen Yonghong smiled honestly and touched the top of his head. He had shaved his hair when he first entered the Section 8 construction site the year before last. He still remembers that his daughter, already in middle school, found it ugly and complained to him for quite a while. But since entering Section 8, Chen Yonghong has had fewer and fewer chances to see his family, sometimes unable to go home for months when busy. He remembers that in early January this year, when the shield machine was about to cross a major risk source, the Beijing-Harbin Railway, he and his colleagues set up a tent in front of the railway, wrapped themselves in military coats, and used electric heaters for warmth. They did not move for half a month, monitoring, measuring, summarizing, and reporting 24 hours a day. In the end, they successfully crossed 8 railway tracks without any mishap.

　　Wang Xinchun, deputy director of the East Main Canal Project Department, told the reporter that the East Main Canal project crosses 37 special and first-level risk sources, including expressways, railways, subways, and viaducts, and 35 have been successfully crossed so far. In addition, the East Main Canal also crosses 18 rivers, including major urban flood discharge and drainage channels such as the Qinghe Diversion Canal, Tonghui River, Liangshui River, and Ba River.

　　In addition, after the shield machine completes excavation, segments are assembled, which is the primary lining construction. After the primary lining is completed, a secondary lining of reinforced concrete is poured on the inner wall to complete the water transmission pipeline. "There will be some water pressure in the pipeline buried underground, so it must be able to resist external soil pressure and prevent internal water from seeping out." Wang Xinchun gave an example: if a hole were drilled in the water transmission tunnel, calculations show that a water column more than ten meters high would spray out. Therefore, the 30-centimeter-thick primary lining segments and the 40-centimeter-thick secondary lining inner wall serve to provide external support and withstand the internal water pressure, respectively.

　　Explanation

　　Where does the river water go after entering Beijing?

　　After the water from the Danjiangkou Reservoir enters Beijing, what is its actual route?

　　According to a responsible person from the Beijing South-to-North Water Diversion Office, the South-to-North Water Diversion Project has three routes: the East Route, the Middle Route, and the West Route. The one that will supply water to Beijing after this year's flood season is the Middle Route, which diverts water from the Taocha Canal Head Gate of the Danjiangkou Reservoir and flows all the way north to Beijing by gravity. The water supply scope includes Henan, Hebei, Tianjin, and Beijing, with a total length of 1,276 kilometers from the starting point to Beijing.

　　After the river water enters Beijing from Hebei, it first enters the Huinanzhuang Pumping Station through the Beijuma River Canal Head in Fangshan, and then is pushed through PCCP pipes (prestressed concrete cylinder pipes) to the Daning Pressure Regulating Pool west of the Yongding River. After stabilization, it splits into two routes: one will cross the Yongding River, pass through Fengtai, and go north along the West 4th Ring Road to the Tuancheng Lake Regulation Pool; the other will go east into the South Main Canal and the East Main Canal, ultimately forming a water supply ring system with the West 4th Ring Road and the North, East, and South 5th Ring Roads as the ring belt. This water transmission "giant dragon" can supply water to various water plants along the route, mainly including the No. 9 Plant, No. 10 Plant, Tongzhou, Yizhuang, Huangcun, and Guogongzhuang water plants. After treatment by the water plants, it is delivered to the urban water supply network and finally to thousands of households.

　　Which areas can use the river water?

　　The starting point of the East Main Canal project that the reporter visited on site connects to the north side diversion outlet of the Guanxizhuang Pumping Station of the Tuancheng Lake to No. 9 Water Plant Water Transmission Project, and the endpoint connects to the South Main Canal project at the Yizhuang Regulation Pool, with a total length of 44.7 kilometers. The recently completed South Main Canal project runs from the end of the Yongding River inverted siphon in the Beijing section of the Middle Route Main Canal along the South 5th Ring Road from west to east, ending at the Yizhuang Regulation Pool, with a total length of nearly 30 kilometers.

　　In the urban area of Beijing, the four parts—the urban section of the South-to-North Water Diversion Main Canal, the South Main Canal project, the Tuancheng Lake to No. 9 Water Plant Water Transmission Project, and the East Main Canal project—together form a ring-shaped water supply route.

　　In addition to transmitting water to the central urban area, the "giant dragon" also shoulders the task of transmitting water to surrounding new towns. For this purpose, diversion outlets have been set up in the South Main Canal and the East Main Canal respectively. The South Main Canal has four diversion outlets: Huangcun, Guogongzhuang, Gaojiabao, and the New Airport; the East Main Canal has four diversion outlets at the No. 8 Water Plant, No. 10 Water Plant, Tongzhou Water Plant, and Yizhuang Water Plant. Underground pipelines have been reserved to supply water to these diversion outlets.

　　It is expected that after the East Main Canal project is connected at the end of April and early May, this main water supply ring in the central urban area will be fully connected, and then the East Main Canal and South Main Canal will successively undergo trial water transmission. After this year's flood season, this "giant dragon" will become the main water transmission channel for river water entering Beijing, continuously delivering clean water to the central urban area and surrounding new towns.