Lu Yanan
Walking beneath the iconic Badaling section of the Great Wall, few tourists realize that just below this World Heritage site lies the construction of the longest tunnel for the Beijing-Zhangjiakou High-Speed Rail Line, set to open by the end of 2019. Unlike typical tunnel projects, this one isn't constructed with a shield machine but relies instead on a blasting method. And yes, they’ve had to “blow things up†more than ten times already!
I decided to visit this mysterious site 102 meters below ground to learn more.
The construction area is a staggering 36,000 square meters, making it Asia's deepest and largest underground high-speed rail station. Travelers will transfer 100 meters underground.
At the tunnel entrance, the smell of diesel and sulfur hit me hard. The dim lighting made the new Badaling Tunnel look like a labyrinth, with intersecting paths and confusing directions. Without markers indicating the intersections, it would have been easy to get lost.
Even though I've reported on many tunnels before, this one felt different. The sheer complexity of the caverns is unmatched. Chen Bin, commander of the China Railway Fifth Bureau North China Command, explained, "This tunnel is not only the longest on the entire line but also houses the Badaling Great Wall Station. Not only do we need to build three levels of underground structures, but also construct 78 large and small caverns. There are as many as 88 caverns, with dense junctions. This makes the Badaling Great Wall Station the most complex underground tunnel group station in China."
Stretching 12.01 kilometers, the new Badaling Tunnel runs between Nankou Town and Yanqing District in Changping, Beijing. It’s a crucial project of the Beijing-Zhangjiakou High-Speed Rail, with its shallowest point only 4 meters below the surface and the deepest at 432 meters.
The Badaling Great Wall Station within the tunnel spans 36,000 square meters and is 102 meters below ground. Once completed, it will be the deepest and largest mountain underground train station in Asia. The station is divided into three levels from bottom to top: the platform level, the entry level, and the exit level (equipment level). This layout ensures smooth passenger flow by keeping incoming and outgoing visitors separate.
Is it practical for passengers to navigate such a deep station? Is it safe?
"Despite the 100-meter underground transfer, it’s still convenient and safe for passengers," explained Dai Yongzheng, deputy manager of the China Railway Fifth Bureau’s Beijing Zhangjiao High-speed Rail Standard Project Department. The station’s design features channels that fully separate incoming and outgoing traffic, ensuring balanced entry and exit points. For the first time in China, advanced equipment like escalators and inclined elevators will be used, raising passengers 62 meters vertically. This makes the Badaling Great Wall Station the highest domestic high-speed rail underground station with passenger lifts. Moreover, the station incorporates a circular rescue corridor design, turning temporary construction wells into permanent rescue channels, ensuring quick emergency response without dead-end conditions.
Progress has been slow but steady. Workers often spend hours grinding the excavator blades, which now take 7 to 10 days to sharpen compared to a month earlier.
Driving through the tunnel feels like fighting the rocks themselves. The Badaling Tunnel is truly a challenge of "hard bones."
On April 15, 2016, during the first day of construction, the excavator hit a snag, revealing the complexity of the task ahead. According to survey designs, the Badaling tunnel primarily targeted second- and third-grade surrounding rocks, expecting daily progress of 6 to 8 meters. But reality showed otherwise—each blast revealed at least four or five layers of rock, requiring the erection of steel frames, mesh, and shotcrete after every blast. This complicated the process, cutting the progress down to just 2 meters per day.
Building the Badaling Tunnel faced "three mountains": geological complexity, undulating terrain, and frequent underground water surges.
Geological instability posed a significant risk. The area contains developed fault structures, with two faults running through it. There are also high risks of rock bursts, collapsible loess, and soft rock deformation. Any slight misstep could lead to collapse.
The terrain was another challenge. As the tunnel crosses Jundu Mountain, the sides are steep and the terrain uneven. The width of the inclined shafts entering the main tunnel construction area is only 7.5 meters, with a height of 6.5 meters, too small for a large-diameter shield machine. Additionally, the inclined shafts had to follow the mountain slope, making sharp turns to reach the construction surface.
"The No. 1 inclined shaft turns over 80 degrees, and the No. 2 shaft turns over 135 degrees. Such a shield machine can't handle such large-angle turns in such a confined space. Thus, we had to resort to blasting methods," said Dai Longzhen.
Water was another adversary. Underground construction fears encountering rivers or groundwater. A sudden water surge could flood equipment and endanger workers. In the Badaling Tunnel area, the fluctuating terrain and seasonal changes mean groundwater can unpredictably emerge, with a daily inflow of nearly 19,000 cubic meters—equivalent to draining 10 standard Olympic-sized pools daily, not to mention the peak inflow of 56,000 cubic meters.
"To tackle these challenges, we not only need courage and caution but also technological innovation," noted Dai Longzhen. The project team employed nano-shotcrete to enhance initial support strength. They also pioneered the "product"-shaped segmental excavation method, including advanced drilling, layered excavation, core retention, key locking, and high-performance concrete pouring, providing new insights for future large-span tunnel construction.
Over 4,500 explosions have occurred since construction began.
"Blasting at the foot of the Great Wall," they use precise micro-blasting technology, minimizing each blast’s impact.
Standing near the tunnel’s corner, I heard the sharp whistle signaling撤离. Blaster Zhang Menghua cautiously approached the bunker as others evacuated. Nearby, someone shouted, "Watch your feet and evacuate quickly!"
At 14:38, workers gathered 200 meters from the blast site. The noise of drills, wheels, and machinery filled the tunnel.
"5, 4, 3, 2, 1… BOOM!" The loud explosion sent a shockwave through my body. Dust slowly drifted out of the hole.
"This was a small blast of 68 kg of explosives. Some blasts exceed 200 kg, much more intense!" Zhang Menghua reassured me. "Don’t worry, the doses are controlled. We prioritize worker safety and protecting our ancestors' legacy."
Zhang Menghua’s words echoed in my mind. The Great Wall stands nearby, and the tunnel passes under it twice, just 4 meters from the Qinglongqiao Station on the Beijing-Zhangjiakou Railway. Balancing tight schedules, multiple work fronts, and daily blasts required precision.
Precise micro-blasting minimizes vibrations. Traditional methods produce high-amplitude vibrations, akin to shaking a glass window when a car idles. Electronic detonators absorb shocks, reducing vibration amplitudes and decibels. Controlled at around 0.16 cm/s, each blast mimics walking on the Great Wall.
Static micro-blasting reduces disruptions. Near Qinglongqiao Station, where the tunnel is only 4 meters deep, workers use expansion agents in drill holes to slowly crack rocks before manual excavation. This protects the Beijing-Zhangjiakou Railway from interference.
Even without nearby relics, blasting remains challenging due to narrow caverns. Some sections are only 2 meters thick. Failure means tunnel collapse. The project team uses pre-stressed anchors to stabilize weaker rock formations and employs real-time monitoring to minimize construction impacts.
"Since the start of this year until July 27, the tunnel has been blasted over 4,500 times, with all data normal. I personally visited the Badaling Great Wall and couldn’t feel any ground movement. I’m excited to see the high-speed rail coexist with the Great Wall!" Zhang Menghua said.
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