In the heart of China, researchers are unraveling a critical challenge that could reshape how we approach deep excavations, particularly in the energy sector. Chao-Feng Zeng, a geotechnical engineer at the Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring, has led a groundbreaking study that sheds new light on the behavior of diaphragm walls during dewatering processes. The findings, published in the journal Underground Space, which translates to ‘Underground Construction’ in English, could have significant commercial implications for energy infrastructure projects worldwide.
Deep excavations are a staple in the energy sector, from constructing power plants to building underground storage facilities. However, these projects often require dewatering to create a dry working environment. Traditionally, significant wall movements were thought to occur only during bulk excavation. But Zeng’s research, conducted at the School of Civil Engineering, Hunan University of Science and Technology, challenges this notion.
“Our experiments showed that lowering pore water pressures inside a diaphragm wall enclosure before bulk excavation can cause wall movements of several centimeters,” Zeng explains. This movement occurs because dewatering reduces pore water pressures inside the enclosure more than outside, causing the wall to act as an unpropped cantilever supported only by the soil.
The implications for the energy sector are substantial. Deep excavations for energy infrastructure often involve significant dewatering, and understanding the potential for wall movements can help prevent costly delays and structural failures. “The lateral effective stresses in the shallow soil behind the wall are reduced, while those in front of the wall increase,” Zeng notes. This stress redistribution can lead to unexpected wall deflections, posing risks to the overall stability of the excavation.
The study, conducted on a laboratory scale, demonstrated small lateral movements. However, Zeng warns that these movements could be proportionately larger in the field, especially with less stiff soil and greater dewatered depths. This is a crucial consideration for energy projects, which often involve complex soil conditions and deep excavations.
So, how can the energy sector mitigate these risks? Zeng suggests implementing a staged dewatering system coupled with phased excavation and propping strategies. This approach enhances the stiffness of the wall support system and allows for dynamic adjustments based on real-time displacement monitoring data. “By carefully managing the dewatering process and continuously monitoring wall movements, we can significantly reduce the risks associated with deep excavations,” Zeng advises.
The research published in Underground Construction offers a roadmap for future developments in the field. It underscores the importance of understanding the intricate interplay between dewatering, soil behavior, and wall movements. As the energy sector continues to push the boundaries of deep excavations, this knowledge will be invaluable in ensuring the safety and efficiency of these projects.
For energy companies, the message is clear: incorporating these findings into their excavation strategies can lead to more stable, cost-effective, and timely project completions. As Zeng’s work gains traction, it could revolutionize how we approach deep excavations, not just in the energy sector, but across all industries that rely on underground construction. The future of deep excavations is evolving, and Zeng’s research is at the forefront of this change.