The Lugeon Test: Methodology, Interpretation, and Applications in Geotechnical Engineering

The Taklamakan Desert, aptly nicknamed the "Sea of Death" in the local Uyghur language, is one of the world's largest, hottest, and driest shifting-sand deserts, comparable in size to Germany. For decades, its vast, unyielding dunes, some towering up to 300 meters, fueled devastating sandstorms that swept across China. Building infrastructure, let alone highways, through such a hostile and remote environment where temperatures can exceed 50 degrees Celsius, presents an almost insurmountable engineering challenge. Yet, China has achieved this feat, demonstrating remarkable human ingenuity and long-term commitment in its quest to connect regions and combat desertification.

The Tarim Desert Highway: A Pioneering Route

The cornerstone of this ambitious undertaking is the Tarim Desert Highway, also known as the Cross-Desert Highway or Taklamakan Desert Highway. This project was initiated primarily to support the burgeoning petroleum industry in Xinjiang, providing a direct and efficient route for oil and gas transportation across the desert, where significant reserves exist in the Tarim Basin. The main segment, the Lunmin Highway, is a monumental achievement in its own right.

• Length and Scale: The Lunmin Highway stretches 552 kilometers (343 miles), with approximately 446 kilometers (277 miles) traversing uninhabited areas of shifting sand dunes, making it the world's longest highway of its kind through moving sands.
• Construction Timeline: Construction commenced in 1993 and was completed remarkably quickly in 1995.
• Purpose: It connects Luntai in the north to Minfeng in the south, significantly shortening travel times across the desert, which previously required extensive detours lasting up to two days.

Combating the Sands: Green Infrastructure and Constant Maintenance

One of the most formidable challenges faced by engineers was the relentless movement of sand, which could easily bury the highway. The solution devised was an innovative and massive greening project:

• Vegetation Belt: To anchor the sand and protect the highway, drought-resistant bushes and trees, such as various types of willow and saxaul, were extensively planted along both sides of the road. This vegetation belt extends approximately 70 meters wide and covers a total area exceeding 3,000 hectares, with about 400 kilometers of the highway lined with these plants. More broadly, a 430-kilometer-long belt of vegetation has been established around the Tarim Desert Highway to protect it from sandstorms.
• Grass Grids and Barriers: On newer desert highways, such as the one connecting Yuli and Qiemo, constructors have deployed an impressive 58 million square meters of grass grids and over 900 kilometers of barriers to prevent the road from being buried by sand. Similar methods are also employed for railway lines, with 50 million square meters of grass and 13 million shrubs and trees planted along the railway to counter sandstorms, achieving an 85% survival rate for plants. These grids stabilize the sand, allowing plants to grow and further secure the area.
• Artificial Irrigation System: Sustaining this vast expanse of vegetation in one of the driest places on Earth required an equally monumental irrigation system. Water is pumped from an aquifer at depths exceeding 100 meters, tapping into a vast underground "sea". Despite the water containing a large amount of dissolved salts, the selected plants have managed to survive.
• Maintenance Stations: The ongoing preservation of this green belt is critical. Special maintenance sheds are strategically located every four kilometers along the entire length of the highway. These stations are staffed by dedicated workers, often couples, who are responsible for irrigating the shrubs and performing daily checks. They live in remote conditions, with drinking water delivered every 20 days. Approximately 100 workers are employed at these stations.

Advancements: Zero-Carbon Energy and Expanding Network

China's commitment to sustainable development in the desert continues to evolve:

• Zero-Carbon Desert Highway: The Tarim Oilfield has pioneered China's first zero-carbon desert highway within the Taklimakan Desert. This project is the longest photovoltaic (PV) demonstration initiative for irrigation and sand control. As of June 2024, it had generated over 5 million kilowatts of green electricity. The project incorporates 86 PV power stations that provide electricity to irrigate more than 3,100 hectares of ecological protection forests, offering a comprehensive alternative to diesel power pumping. All 109 water wells along this highway now use clean electricity for pumping. This green project is estimated to reduce diesel fuel consumption by about 1,000 tons and carbon dioxide emissions by about 3,410 tons annually, aligning with China's dual carbon goals.
• Expanding Highway Network: Beyond the pioneering Tarim Desert Highway, China has continued to expand its network of roads across the Taklamakan. The total length of highways traversing the desert now exceeds 1,200 kilometers. This includes:
  • The second highway, connecting Alar to Hotan, completed in 2007.
  • The third highway, linking Yuli County and Qiemo County, opened in 2022. This 334-kilometer highway (with 307 km through the desert) was a significant undertaking, involving leveling 32 tall sand dunes and filling 28 low-lying lands.
  • A fourth highway, connecting Tumxuk and Kunyu, also opened in 2022.
• Railway Loop: Further solidifying connectivity, China also built the world's first railway loop around a desert – the 825-kilometer Hotan-Ruoqiang line. This "hero Railway" was completed in 2022 and provides a complete loop around the Taklamakan Desert, connecting Western and Inland regions and strengthening Xinjiang's position as a vital communication hub.

Broader Impact and Future Implications

These desert highway projects are more than just engineering marvels; they are integral to China's larger "Three-North Shelterbelt" project, often referred to as the "Great Green Wall," which began in 1978 to combat desertification and sandstorms. While challenges like low tree survival rates and persistent sandstorms remain, these efforts have demonstrably increased China's forest coverage to over 25% by the end of last year, a significant improvement from 10% in 1949.

The highways have had tangible economic and social impacts, significantly shortening travel distances and reducing costs for local communities, boosting confidence for enterprises to invest in previously isolated areas. They are a critical part of China's "Go West" strategy, aiming to reduce the economic gap between its less developed Western regions and the wealthier Eastern parts.

The experience gained by Chinese specialists in building and maintaining infrastructure in such extreme desert conditions could prove invaluable globally. With predictions of climate change leading to the transformation of some green areas into deserts, the engineering solutions developed in the Taklamakan offer crucial lessons for future global environmental challenges.