On April 9, gusts of spring wind blew through the gullies of the Loess Plateau in northern Shaanxi, where machinery roared and crowds bustled inside the tunnels under construction.

As a key project of the national "Eight Vertical and Eight Horizontal" high-speed rail network's Baotou (Yinchuan)–Haikou corridor and Shaanxi's "Mi"-shaped high-speed rail network, the approximately 239-kilometer Yan'an–Yulin high-speed railway is under intense construction. Thousands of builders are launching fierce assaults on geological "roadblocks" and construction "hard bones" along this treacherous route with a bridge-tunnel ratio exceeding 94%, using wisdom and sweat to open up a "steel artery" that accelerates development of the old revolutionary base areas of northern Shaanxi.

Geological "Hard Bones": Extreme Challenges on the Loess Plateau

"As of the end of March, the project has completed cumulative investment of over 8 billion yuan, tunnel excavation has exceeded 64,000 meters, more than 12,000 bridge pile foundations have been completed, and multiple controlling works have achieved breakthrough progress," introduced Ma Yi'an, commander of the Yan'an–Yulin high-speed railway construction command headquarters of Xicheng Passenger Dedicated Line Shaanxi Company.

The Yan'an–Yulin high-speed railway starts from Yulin South Station in the north and ends at Yan'an Station in the south, running vertically through the loess ridge-and-gully region of northern Shaanxi. The line's 50 tunnels and 68 bridges interweave into "two networks above ground and below ground," with a bridge-tunnel ratio as high as 94.3%, making it tantamount to building a high-speed railway inside a "geological museum." Complex geology is the biggest "bottleneck": tunnels along the entire line mostly pass through loose loess strata, with landslide, slump, and shallow-burial adverse geological sections densely distributed; in some sections the minimum burial depth is only 2 meters, and the risk of arch crown exposure is extremely high. The line's longest tunnel, Tongbaiyuan No. 1 Tunnel, with a total length of 14,616 meters, consists mainly of Grade III to Grade VI surrounding rock and is the longest loess high-speed rail tunnel in China; the entrance section of Jiulishan Tunnel is the only Grade VI surrounding rock on the entire line, where the fragmented soil mass has extremely poor stability, and the risk of cracking and collapse of the side and face slopes constantly threatens construction safety.

"Every step forward is like 'drilling a hole in tofu.'" On April 9, Jia Kebao, project manager of the Yan'an–Yulin high-speed railway project of China Railway 14th Bureau Group, admitted frankly that during construction of Miaoshan No. 1 Tunnel, the working platform was narrow and large machinery was restricted, and when passing through slump and landslide sections, the surrounding rock could become unstable and deform at any moment. In the Yulin section, the 34.5 tunnels have a total length exceeding 107 kilometers, with adverse geological sections accounting for more than 70%; deformation, falling blocks, and collapses occurred frequently during construction, and one tunnel once settled more than 20 centimeters within 3 hours after excavation, requiring the technical team to carry out emergency rescue overnight to avert danger. In addition, the line passes through ecologically sensitive areas and water source protection zones and runs close to important facilities such as optical cables and coal transport pipelines; the combined pressure of environmental and water conservation and construction coordination makes construction even more difficult.

"To advance construction efficiently, the project team innovatively adopted a 'smart + mechanized' construction model, deploying new intelligent lining trolleys to achieve visual, intelligent, and information-based control of lining construction. Simultaneous excavation at multiple working faces has greatly improved construction efficiency," said Zhang Penghui, chief engineer of the Yan'an–Yulin railway project of China Railway 20th Bureau Group.

Tackling Key Problems with a "Combination Punch": Technology Empowers Solutions to Construction Challenges

Facing multiple difficulties in geology, safety, and coordination, all participating parties have united as one, launching a "combination punch" of technological innovation, management efficiency improvement, and coordinated attack. Central enterprises such as China Railway 14th Bureau Group, China Railway 11th Bureau Group, China Railway Third Bureau Group, China Railway 20th Bureau Group, and China Railway Tunnel Group have formed "spearhead teams" and "assault teams" to focus on targeted breakthroughs at difficult points.

At Jiulishan Tunnel, the project team advanced simultaneously at 6 working faces through "dual inclined shafts," with more than 500 workers and 200 machines operating in 24-hour shifts, tripling the excavation speed and successfully surpassing the 5,000-meter mark in early April. Miaoshan No. 1 Tunnel innovatively adopted a "short excavation, fast cycle" model, integrated BIM technology to build a three-dimensional model, simulated the entire construction process in advance, dynamically optimized the plan, and achieved visual control, allowing the 672-meter tunnel to be safely completed in just 8 months.

The entire Yan'an–Yulin high-speed railway has built an intelligent construction management platform, promoting the use of advanced equipment such as digital intelligent lining trolleys, three-dimensional laser scanning, and emergency control robots. The Yulin beam fabrication yard of China Railway 11th Bureau Group has created a "smart beam yard," achieving dynamic management of the entire process of raw materials, production, and quality through an information control platform, raising the prefabrication efficiency of the first box girder by 40%. Mengjiacha No. 1 Tunnel applied an advanced geological prediction system to accurately predict changes in surrounding rock, achieving breakthrough with "zero collapse and zero accidents." Intelligent monitoring systems cover all work sites along the line, with grid inspectors on 24-hour duty and construction data uploaded in real time, keeping safety and quality fully controllable throughout.

The construction unit took the lead in establishing a "daily scheduling, weekly meeting, monthly assessment" mechanism, and jointly with design, construction, and supervision units set up a technical research team to solve problems through on-site work. Participating enterprises carried out activities such as "100 Days of Intensive Work" and "labor competitions," comparing progress, quality, and safety, creating a strong atmosphere of "emulation, learning, catching up, and surpassing."

Striving Through the "Golden Period": The Old Base Area's High-Speed Railway Gradually Reveals Its Grand Form

Just after Qingming, the entire Yan'an–Yulin high-speed railway has set off another upsurge of intensive work.

Jinjiagou Tunnel, undertaken by China Railway 20th Bureau Group, is the first tunnel completed in the Yan'an section and has finished lining construction, laying the foundation for subsequent track laying; in the YYZQ-11 bid section of China Railway 11th Bureau Group, 8 bridges are under simultaneous construction, more than 80% of the 4,074 pile foundations have been completed, and numerically controlled reinforcement cage seam welders operate day and night, precisely producing standardized components; in bid section 9 of China Railway Third Bureau Group, after the breakthrough of Mengjiacha Tunnel, the team immediately moved to Tongbaiyuan No. 2 Tunnel, where excavation speed exceeds 15 meters per day.

"From 'blueprints on paper' to 'a thoroughfare on the ground,' every step embodies sweat," introduced Ma Yi'an. In 2026, the Yan'an–Yulin high-speed railway plans to complete investment of 7.45 billion yuan, focusing on advancing tunnel breakthrough, bridge main structures, and subgrade formation works. Up to now, 4 tunnels including Miaoshan No. 1, Jinjiagou, and Mengjiacha No. 1 have been successfully completed, excavation of controlling tunnels such as Jiulishan and Tongbaiyuan No. 1 has passed the halfway mark, and works such as the Qingjian River Grand Bridge and Yulin South Station are proceeding in an orderly manner. It is expected that after completion and opening to traffic in November 2028, the travel time from Xi'an to Yulin will be compressed from 5 hours to 2 hours, ending the history of Yulin having no high-speed rail and helping Shaanxi achieve "high-speed rail in every city."

From loess gullies to a steel dragon, the builders of the Yan'an–Yulin high-speed railway, with the style of "daring to fight tough battles and skilled at winning them," have created construction miracles under extreme conditions. This high-speed railway linking the two major old revolutionary base areas of Yan'an and Yulin is not only a major transportation artery but also an "accelerator" for regional economic development; it will inject strong momentum into the construction of the northern Shaanxi energy and chemical industry base and the rural revitalization of the old revolutionary base areas, writing Shaanxi's chapter in building a transportation powerhouse on the Loess Plateau.

Source: Shaanxi Net