In the heart of Ningbo, China, a groundbreaking study led by YE Ru of the Construction Branch of Ningbo Rail Transit Group Co., Ltd. is shedding new light on the challenges of ultra-deep diaphragm wall construction in soft soil strata. The research, recently published in ‘Chengshi guidao jiaotong yanjiu’ (Urban Rail Transit Research), delves into the intricate dynamics of trench wall stability, a critical aspect of underground station construction that has significant implications for the energy sector and beyond.
The study focuses on the 76-meter ultra-deep diaphragm wall trench section (WE-15) on the east side of Ningci Road Station of Ningbo Metro Line 7. This project, like many others in urban areas, faces complex geological conditions and the ever-present risk of trench wall collapse. YE Ru and his team used PLAXIS 3D finite element software to simulate the trenching process, providing a detailed analysis of the stability characteristics of trench walls in soft soil strata.
The findings are both illuminating and alarming. The research reveals that the horizontal displacement of the trench wall primarily occurs in the early stages of trenching, particularly when excavating the ④2b silty clay layer. This layer, rich in silt content, is highly susceptible to disturbance from repeated excavation with a trenching grab. The process creates adsorption pores in the slurry wall, allowing groundwater to infiltrate and carry local silt deposits, thereby increasing the risk of localized collapse.
“Our simulations showed that the maximum horizontal displacement of the trench wall is 18.18 mm, occurring at a depth of 25 meters below ground level,” YE Ru explains. “This closely aligns with the actual collapse location, highlighting the accuracy of our model and the critical need for targeted solutions.”
The study underscores the significant influence of slurry density and reinforcement measures on trench wall stability. Increasing slurry density and reinforcing the trench wall are identified as effective strategies to control horizontal displacement. These findings have far-reaching implications for the energy sector, where underground infrastructure is crucial for the safe and efficient distribution of resources.
As urbanization continues to drive the demand for underground infrastructure, the insights from this research are invaluable. They pave the way for more robust and reliable construction methods, ensuring the stability and longevity of underground structures. For the energy sector, this means enhanced safety and efficiency in the construction and maintenance of critical infrastructure, ultimately supporting the growth and sustainability of energy projects.
The research published in ‘Urban Rail Transit Research’ is a testament to the ongoing advancements in construction technology and the importance of scientific rigor in addressing complex engineering challenges. As we look to the future, the lessons learned from this study will undoubtedly shape the development of more resilient and efficient underground construction practices, benefiting not only the energy sector but also the broader infrastructure landscape.