In the heart of China’s bustling urban development, a groundbreaking study is set to revolutionize how we approach subway construction, particularly in challenging geological conditions. Led by SHA Lizhong, a prominent figure from China Railway 19th Bureau Group Rail Transit Engineering Co., LTD., this research delves into the intricate world of thermal-hydraulic-mechanical (THM) coupling effects in water-rich sand layers. The findings, published in the esteemed journal Taiyuan Ligong Daxue xuebao (Journal of Taiyuan University of Technology), promise to reshape the future of subway tunnel engineering and beyond.
Imagine the complexity of constructing a subway tunnel beneath a city, where the soil is not just ordinary earth but a water-rich sand layer. This is not a hypothetical scenario but a real challenge faced by engineers in Kunming, China. The solution? Artificial freezing methods, a technique that transforms the soil into a solid, stable structure by lowering its temperature. However, this process is far from straightforward, involving a delicate balance of heat, water flow, and mechanical forces.
SHA Lizhong and his team have tackled this multifaceted problem head-on. They developed a sophisticated three-dimensional model to simulate the THM coupling effects during the soil freezing process. “The synergistic action of heat, flow, and force fields during soil freezing is a critical factor that we need to understand and control,” SHA explains. “Our model allows us to investigate the effects of various parameters, such as cooling plans, groundwater seepage velocity, and formation saturation, on the freezing effect.”
The results are enlightening. The study found that higher groundwater seepage velocity enhances the freezing effect downstream, creating a thicker frozen zone. Different cooling schedules also play a significant role, with a -25°C cooling plan proving to be the most effective. Moreover, the research highlights the impact of frost heave, a phenomenon where soil expands as it freezes, causing vertical and horizontal displacements. “The vertical displacement can reach up to 8.43 mm, which is substantial and can affect adjacent structures,” SHA notes. “Understanding and mitigating these displacements is crucial for the stability and safety of the tunnel.”
The implications of this research extend far beyond subway construction. In the energy sector, where underground pipelines and storage facilities often encounter similar geological challenges, the insights gained from this study could lead to more efficient and safer operations. For instance, the artificial freezing method could be employed to stabilize soil around pipelines, preventing leaks and ensuring structural integrity.
Furthermore, the advanced THM coupling model developed by SHA and his team could be adapted for other applications, such as geothermal energy extraction and carbon sequestration. By providing a deeper understanding of the complex interactions between heat, water, and mechanical forces in the subsurface, this research paves the way for innovative solutions in various fields.
As cities continue to expand and the demand for underground infrastructure grows, the need for reliable and efficient construction methods becomes ever more pressing. SHA Lizhong’s work, published in the Journal of Taiyuan University of Technology, offers a beacon of hope, illuminating the path towards a future where engineering challenges are met with cutting-edge science and technology. The commercial impacts are vast, promising a new era of stability, safety, and sustainability in the energy sector and beyond.
