The waters along the Jinsha River are warmly flowing, and the geophysical exploration elite are battling on the plateau—A report on the Yunnan Wulu Expressway Wide-Area Exploration Project.

“I,” filled with reverence for “Colorful Yunnan,” followed the banks of the Jinsha River and entered Luquan Yi and Miao Autonomous County.

Looking into the distance, the clouds at the horizon are pure and pristine, with rolling mountain peaks stretching into the middle distance, and the Jinsha River below gleaming a vivid green. As you hike along, you’ll pass through metamorphic rocks from the Lower Proterozoic Era—dating back over 2 billion years—through Cambrian limestone from 500 million years ago, and finally to Triassic sandstone and shale from 200 million years ago, with altitudes ranging from 1,500 meters to 3,000 meters.

“I” am nestled in the mountains’ embrace, and the mountains gaze back at “me.” As a fierce gust of wind sweeps through, howling wildly amid swirling sand and dust, several red figures—each carrying instruments and lugging battery packs—continue to stride forward with unwavering determination toward the survey coordinates. “I” am nestled in the mountains’ embrace, and “I” look up at the mountains. When we reach the sheer cliffs where streams and trees have vanished from sight, those few red figures, each bearing coils of wire and carefully laying out survey lines along the designated paths—these are the most beautiful sights this mountain has to offer. The gnarled vines and ancient trees are the mountain’s true, unadorned face; and the silhouettes of people, clad in red shirts and red pants, forging their way along winding trails—these are the mountain’s most exquisite embellishments.

As “warriors” of the Geophysical Exploration Institute, driven by a passionate commitment to contributing to our nation’s infrastructure development, we’ve arrived at the banks of the Jinsha River—dedicated to completing the surveying work for four tunnels along the Yunnan Wudongde–Luquan Expressway: Wudongde, Aqiao, Samaji, and Dapingzi. Given the project’s tight schedule, rugged terrain, and dense network of high-voltage power lines, we’ve chosen the wide-area electromagnetic method—the latest and most cutting-edge technology in the geophysical exploration industry—as our key攻关 technique for this project. To carry out this mission, we’ve assembled a team composed of specialized technical personnel from fields such as geophysical exploration, geology, surveying, and electrical engineering, as well as dedicated drivers.

High-voltage power lines are the primary factor affecting electromagnetic methods. Most of the survey sections across the four tunnels are located in areas with a high density of such lines. The project team is somewhat uncertain about whether the wide-area electromagnetic method can effectively suppress interference from 500-kV high-voltage lines and obtain high-quality data. However, company leaders encouraged us, saying, “It’s precisely when we face difficulties that we can reap rewards; it’s precisely when we encounter challenges that we’re truly tested. No matter how tough the obstacles may be, we must find every possible way to overcome them—this is exactly the spirit of our geophysical exploration ‘iron army’!”

Through field tests using the wide-area electromagnetic method, the project team proposed a technical solution to address interference from high-voltage power lines: increasing the transmit current while simultaneously shortening the signal transmission distance. This solution effectively suppressed the interfering signals, enabling the collected data to achieve excellent quality.

Through close cooperation and seamless coordination among the various teams within the project department, we swiftly completed this project while ensuring safety, maintaining quality, and meeting the scheduled timeline—achieving our goals of high efficiency, superior quality, and zero accidents. Meanwhile, the interim results and the quality of fieldwork have received unanimous praise from the client, the Yunnan Institute of Traffic Planning and Design.

The completion of this project not only promptly addressed the client’s need to deploy deep boreholes along the Wulu Expressway but also provided a valuable case study for the application of wide-area electromagnetic methods in high-altitude, mountainous regions characterized by dense and intense electromagnetic interference.

Executive Producer | Zhang Guangda
Reviewed by | Zhou Huiying
Text | Li Gaozhao, Tan Zhangkun
Figure | Yang Fengjian, Jiang Shengwu
Editor | Wen Han