Lu Yanan As the summer season approaches, visitors to the Great Wall at Badaling will be woven. I am afraid that few tourists know that just under the core area of ​​the Badaling Great Wall World Heritage Site is the construction of the longest tunnel of the Beijing-Zhangjiakou High-speed Rail Line, which is about to open at the end of 2019. This tunnel is not constructed using the popular shield machine, but it is a blasting method. Even one day it will be "fried" for more than ten times! Hey, this is really "too old to use earth!" One day in July, the reporter put on a hard hat and a protective mask and walked into the mysterious site 102 meters below the ground to find out. Cartography: Shen Yizheng Construction area of ​​36,000 square meters This huge underground maze will be the deepest and largest underground high-speed rail station in Asia. Passengers will transfer 100 meters underground. At the entrance to the tunnel, the pungent smell of diesel and sulphur rushed together. In the dim light, the construction of the new Badaling Tunnel at the Beijing-Zhangjiakou High-speed Railway is like a huge maze. The crossings are interlaced, seven twists and eight turns. From time to time, there are 3m high excavators, 2m high forklifts, and various transportation materials. Pickups pass by. If it weren’t for the small tube well markings above each intersection, I’m afraid I’ll be lost. The number of tunnels the reporter had interviewed also had double digits. In the past, there were not many tunnels in the tunnel. Why is the cavern in the new Badaling tunnel so complicated? “The new Badaling Tunnel at the Beijing-Zhangjiagang High-speed Railway is not only the longest tunnel on the whole line, but also has the Badaling Great Wall Station. Therefore, not only three-story underground structures but also 78 large and small caverns must be built in the tunnel. As many as 88, and the cavern junctions are so dense, the Badaling Great Wall Station has become the most complicated underground tunnel group station in China.†said Chen Bin, commander of the China Railway Fifth Bureau North China Command. The new 12.01-kilometer new Badaling Tunnel is located in the section between Nankou Town and Yanqing District in the Changping District of Beijing. It is a key project and control project of the Beijing Zhangjiao High-speed Railway. The distance between this tunnel and the ground is only 4 meters in the shallowest part and 432 meters in the deepest part. The Badaling Great Wall Station in the tunnel covers a building area of ​​36,000 square meters. The track is 102 meters away from the ground. Upon completion, it will become the world's deepest and largest mountain underground train station in Asia. According to the design, the station is divided into three underground structures, which are the platform level, the entry level and the exit level (equipment level) from bottom to top. This ensures that visitors to and from the station will not meet each other and the passenger flow will be smoother. Is it convenient for passengers to enter and exit at such a deep station? Can you guarantee safety? “Although there is a 100-metre underground transfer, it is convenient and safe for passengers to get in and out of the station.†Dai Yongzheng, deputy manager of the China Railways Fifth Bureau’s Beijing Zhangjiao High-speed Rail Standard Project Department, introduced the station’s many innovative designs. The form of the station channel realizes the complete separation of passengers entering and exiting the station and the balanced arrangement of the entry and exit points. For the first time, the use of advanced equipment such as escalators and inclined elevators will be promoted once. The vertical height of passengers will reach 62 meters, which will make the Great Wall Station of Badaling become the highest high-speed railway underground station with the highest domestic passenger lift. More importantly, for the first time, the station adopted a circular rescue corridor design, “turning waste into treasureâ€, turning the inclined construction well assisted by construction and depreciation into a permanent rescue channel, enabling this large-scale underground station to be equipped with a rapid emergency without an emergency. Dead-end rescue conditions. Drive up to 2 meters a day Drain at least 10 standard 8 pools per day Walking in the tunnel, from time to time, workers were seen using electrical gear to grind the excavator's shovel and sparks splashed. Yang Jiachuan, who had been working on tunnels for 20 years, pointed to a row of slick blade tips and reluctantly ridiculed himself: “The tunnel was dug for so many years. This place is really the hardest 'hard bones'! Look at this shovel and dig around the surrounding rocks. Only need to grind it once a month. Now it takes 7 to 10 days to grind!" To open a tunnel is to fight against the rocks, and the Badaling Tunnel puts "hard bones." On the first day of construction on April 15, 2016, the excavator went on a shovel and the project department discovered that it was "winning." “As soon as the excavator digs, we know that the construction difficulty is at least doubled.†Jiang Si, project manager of the China Railway Fifth Bureau’s Beijing Zhanggao High-speed Railway Three Standards Project Division, explained that according to the survey and design drawings, the Badaling tunnel mainly attacked the second- and third-grade surrounding rocks, then one day. At least 6 meters to 8 meters can be advanced, but a hole is found and the surrounding rock is at least four or five. “Each time after blasting, steel frames, hanging steel mesh, and shotcrete should be erected. The process is complicated and the working time must be doubled. The maximum amount of excavation is 2 meters a day.†In fact, the construction of the Badaling Tunnel at the Beijing-Zhangjiakou High-speed Railway does face “three mountainsâ€. Geological complexity is easy to collapse. In the area where the Badaling tunnel is located, geological fracture structures are relatively developed. The cavern passes through two faults, and there are high-risk geology such as rock bursts, collapsible loess, and large deformation of soft rocks. This is a very high-risk construction project and is slightly inadvertent. It will cause collapse. The terrain is quite undulating. As the tunnel crosses Jundu Mountain, both sides are high in the middle and the terrain is undulating. On the one hand, the cross-section of the inclined shaft entering the main battlefield of the tunnel construction is too small. The width of 7.5 meters and the height of 6.5 meters cannot accommodate the large-diameter shield boring machine. On the other hand, the inclined shaft must follow the slope of the mountain and experience great Turn to enter the tunnel construction surface. “The No. 1 inclined well turns more than 80 degrees, and the No. 2 inclined well turns more than 135 degrees. This kind of shield tunnelling machine is a hundred meters at a time, and even a thousand kilometers of giants cannot complete such a large angle turn in such a small area. Therefore, this tunnel can only use the blasting method." Dai Long Zhen said. Gushing water frequently occurs underground. Underground construction is most afraid of meeting dark river or groundwater. The sudden gushing of water in the air guns will not only drown the machinery and equipment and affect personal safety. High water pressure may also cause landslides. The depth of groundwater in the construction area of ​​the Badaling Tunnel is precisely based on topography fluctuations and a wide range of seasonal changes. I do not know where it will pop up a "big fountain", normal daily water inflow of nearly 19,000 cubic meters, equivalent to a day to drain The water storage capacity of 10 standard 8 swimming pools, not to mention the largest daily water volume of 56,000 cubic meters. “It is precisely because the construction environment is very complicated. To tunnel here, we must not only be bold and careful, but also rely on technological innovation.†According to Dai Longzheng, the project department designed the use of nano-shotcrete to enhance the initial support strength, especially In the transition span of large spans, the "product"-shaped segment excavation method has been created, which includes advanced drilling, layered excavation, reserved core, key locking, and high-performance concrete pouring. The method provides blasting for the construction of large-span tunnels in the future. New wisdom. Has exploded more than 4,500 times "Blasting at the foot of the Great Wall", using precision micro blasting technology, each blasting only equals the foot on the Great Wall. “In a moment there was a small explosion, and you listened to the command and waited at the bunker at the corner of the tunnel.†The voice of Dai Long Zhen did not fall, and a harsh long whistle sounded in a tunnel 100 meters away. It turned out that the demolition team had buried the detonator and began to leave the field, leaving only Zhang Menghua, the blaster. Zhang Xuehua whistled while slowly extending his hands to the bunker and whistled; the tall, strong man on the side shouted while waving a flashlight, “pay attention to his feet and quickly evacuate!†At 14:38, the on-site construction workers gathered at the bunker 200 meters away from the blasting point. The sound of the wind guns, wheel sounds, and sounds of the machine were noisy in the tunnel. "5,4,3,2,1..." "Bang" a loud bang exploded in the ear, the shock wave will be a pressure on the body, the heart seems to want to jump out of the chest. After a long while, a piece of dust drifted out of the hole. "This is the small blast of 68 kilograms of gunpowder. We have more than 200 kilograms of blasts. That shock is even more shocking!" Zhang Xuehua consoled the reporter. "But don't worry, the dose is strictly controlled. Let's pay attention to the workers." Security, but also have to protect the baby left by their ancestors is not?" Zhang Xuehua's mouth is the Great Wall. The Badaling Tunnel on the Beijing-Zhangjiakou High-speed Rail passes through the Great Wall in parallel and twice through the Great Wall of Badaling. It is only 4 meters away from the head of the Qinglongqiao Station on the Beijing-Zhangjiakou Railway. The accumulation of so many "national treasures" poses a challenge to construction, not to mention the tight schedule and heavy tasks, 11 work surfaces working at the same time, firing at least 13 times a day, organizing personnel equipment withdrawals each time, and how to avoid both The concentration of blasting causes resonance and disturbs the surrounding cultural relics, and avoids too large blasting intervals, which affects the construction progress. Precise micro blasting reduces vibration. According to reports, the traditional blasting technology has a high speed of vibration and a strong sense of quake. In the underground 100m operation, the disturbance to the Great Wall is similar to the vibration of a glass window when the car is idling, and the accurate electronic detonator shock-absorbing blasting technology can make blasting vibrations. The amplitude and decibels are minimized. When the speed is controlled at around 0.16 cm/s, each shot is only equivalent to the Great Wall. Static micro blasting reduces disturbances. In the area under the Qinglongqiao station with a depth of only 4 meters, about 40 meters of tunnel construction is to put a special expansion agent at the drill hole of the air gun, so that the rock is slowly cracked, and then artificially excavated, mechanically pushed, to the maximum Land protection Beijing-Zhangjiakou Railway will not be disturbed by underground construction. Even if there are no artifacts around, the blasting of the Badaling Tunnel is also a challenge. Many caverns lead to more blasting at small intervals. The narrowest part of the cavern is only 2 meters thick. Once the blasting fails, it means tunnel collapse. On the one hand, the project department adopts prestressed anchor technology to enhance the stability of weaker rock formations and avoid rock strata. On the other hand, while using electronic detonators for shock absorption, a monitoring team is also set up to monitor blasting vibration speed in real time and reduce The disturbance of the construction to the mountain body. “From the start of the Spring Festival this year to July 27, the tunnel has been blasted more than 4,500 times, and the data is all normal. I myself went to experience the Badaling Great Wall and I really didn’t feel that the ground was being blown. I’m now looking forward to the high-speed rail wearing the Great Wall. A scene!" said Zhang Xuehua.