Lü 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 on the Beijing-Zhangjiakou High-Speed Railway. Scheduled to open by the end of 2019, this tunnel is not built using modern tunneling machines but instead relies on traditional blasting techniques. Imagine the thunderous sound of explosives going off repeatedly—more than ten times a day!
Curious to learn more, I donned my hard hat and protective mask to descend 102 meters underground to explore this remarkable feat of engineering.
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The cartography was done by Shen Yizheng. The construction area covers an impressive 36,000 square meters, making this subterranean labyrinth the largest and deepest high-speed rail station in Asia. Travelers will transfer 100 meters beneath the surface.
At the tunnel entrance, the acrid smell of diesel and sulfur hit me immediately. Inside, the dimly lit maze resembled a warren of endless corridors. Excavators towered over us at 3 meters high, while forklifts and transport vehicles zipped past. Without the small markers overhead indicating each intersection, I would have surely gotten lost.
I’ve reported on many tunnels, but this one felt different. Unlike others, this new Badaling tunnel is extraordinarily complex due to its sheer scale and intricate design.
Chen Bin, Commander of the China Railway Fifth Bureau North China Command, explained, “This tunnel isn’t just the longest on the entire line; it also houses the Badaling Great Wall Station. That means we’re building not only three underground levels but also 78大大å°å°çš„ caverns, totaling 88. The junctions are so densely packed that this station has become the most complicated underground tunnel system in China.â€
Stretching 12.01 kilometers, the new Badaling Tunnel lies within the Changping District of Beijing, connecting Nankou Town to Yanqing District. Its depth varies dramatically—from just 4 meters near the surface to 432 meters at its deepest point.
The Badaling Great Wall Station alone spans 36,000 square meters. Located 102 meters below ground, it will become Asia's deepest and largest underground high-speed rail station upon completion. Designed with three levels—platform, entrance, and exit—the station ensures smooth passenger flow by separating arrivals and departures completely.
But what about convenience and safety for travelers navigating such a deep station?
Deputy Manager Dai Yongzheng assured me, “Even with a 100-meter descent, getting in and out of the station remains safe and convenient.†He highlighted several innovations, including escalators and inclined elevators, which will allow passengers to ascend 62 meters vertically. This makes Badaling Great Wall Station China’s highest high-speed rail underground station with the longest passenger lift. Most impressively, they’ve incorporated a circular rescue corridor—a clever reuse of construction wells—ensuring quick emergency access without dead ends.
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Drilling through rock is no easy task, especially in such challenging conditions.
When construction began on April 15, 2016, things got tough right away. “The moment the excavator started digging,†recalled Project Manager Jiang Si, “we knew the difficulty would double.†According to design plans, the Badaling tunnel primarily targeted second and third-grade surrounding rocks, allowing for daily progress of 6 to 8 meters. But reality proved otherwise. Each blast revealed harder-than-expected rock, forcing crews to spend 7 to 10 days grinding tools that usually lasted a month. At best, they could advance only 2 meters a day.
Building this tunnel wasn’t just about tackling tough rock—it meant overcoming three major challenges: geological instability, uneven terrain, and frequent water seepage.
Geologically, the area is prone to collapse. The tunnel passes through two fault lines, with risks of rock bursts, collapsible loess, and soft rock deformation. Even minor errors could lead to disaster.
The terrain added another layer of complexity. As the tunnel cuts through Jundu Mountain, the slopes on either side are steep. The narrow entrance shaft measures just 7.5 meters wide and 6.5 meters high, far too small for large-diameter tunneling machines. Additionally, the shaft had to follow the mountain’s slope, requiring sharp turns to reach the main construction area.
“The No. 1 inclined shaft turns over 80 degrees, and No. 2 exceeds 135 degrees,†explained Dai Longzheng. “A tunneling machine simply can’t make such sharp turns in such confined spaces. So we’re forced to use blasting methods.â€
Water posed yet another threat. Underground construction dreads encountering rivers or high-pressure groundwater. In Badaling, daily inflows average 19,000 cubic meters—equivalent to draining 10 standard Olympic-sized pools daily. Peak flows exceed 56,000 cubic meters.
Despite these challenges, innovation has been key. The project team used nano-shotcrete to strengthen initial supports, developing a novel “product-shaped†excavation technique for large spans. This method involves advanced drilling, layered excavation, core reservation, key locking, and high-performance concrete pouring, offering valuable insights for future tunnel projects.
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Over 4,500 blasts later, the results speak for themselves.
“Blowing up at the foot of the Great Wall†requires precision micro-blasting techniques. Each explosion is carefully calculated to minimize impact.
Standing 100 meters away, I watched as Zhang Menghua, the blaster, prepared for detonation. “Five, four, three, two, one… BOOM!†The explosion reverberated, sending a shockwave that pressed against my chest. Dust billowed from the hole. Zhang reassured me, “This was a small blast—only 68 kilograms of explosives. Some blasts exceed 200 kilograms!â€
Precision electronic detonators reduce vibrations significantly. While traditional methods might rattle nearby structures like idle cars shaking windows, these new techniques limit vibrations to less than 0.16 cm/s, equivalent to barely touching the Great Wall.
Even without nearby artifacts, blasting remains risky. Narrow caverns require frequent small blasts, some only 2 meters thick. Failure here could mean tunnel collapse. Prestressed anchors stabilize weaker rock formations, while real-time monitoring tracks vibration speeds to mitigate impacts.
By July 27, 2019, the tunnel had been blasted over 4,500 times. “Since the Lunar New Year, everything has gone smoothly,†said Zhang. “I visited the Badaling Great Wall myself, and there was no noticeable ground movement. I can’t wait to see trains running beneath it!â€
This ambitious project underscores China’s commitment to balancing modernity with history.
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