In the heart of China, a groundbreaking study is reshaping the way we think about constructing deep, super-span open cut tunnels. Led by HUANG Jixin of the Lanzhou Urban Construction Design and Research Institute Co., Ltd., and a team of experts from Southwest Jiaotong University, China Railway Chengdu Rail Transit Health Management Technology Co., Ltd., and North Minzu University, this research is set to revolutionize the energy sector’s approach to large-scale tunneling projects.
The study, published in the Journal of Geotechnical Engineering (Yantu gongcheng xuebao), delves into the mechanical characteristics of deep soil-covered super-span open cut tunnels under different unloading measures. The team explored the effectiveness of EPS slabs and concrete columns, used alone or in combination, to reduce the internal force and deformation of these massive structures.
“Our goal was to find the most effective unloading method to enhance the safety and longevity of these tunnels,” said HUANG Jixin, the lead author of the study. The team’s innovative approach involved model testing and a deep analysis of soil pressure, internal force, and displacement of the lining structure. They employed the damage stage method to evaluate the safety of the lining structure, providing a comprehensive assessment of the unloading measures’ impact.
The results were striking. The team found that using concrete columns alone could reduce the average vertical and horizontal earth pressures by 40.01% and 79.34%, respectively. However, this measure significantly reduced the horizontal earth pressure, weakening the soil’s constraint effect on the lining structure. On the other hand, laying EPS boards solely on the top of the tunnel reduced the vertical earth pressure while increasing the horizontal pressure, thereby strengthening the soil’s constraint effect and achieving the optimal unloading effect.
“When we laid the EPS board on the top of the cut-and-cover tunnel, we saw a remarkable reduction in the displacement of the tunnel’s top by 50.15%,” explained HUANG Jixin. The bending moments of the crown and haunch were also reduced by 77.48% and 75.71%, respectively, significantly improving the structural safety.
The study also introduced a novel displacement prediction equation for the weak parts of the lining structure, based on the principle of multiple linear regression. This equation, with a maximum error of just 7.30% and a minimum error of 0.28%, can be a game-changer in the optimization of unloading parameters for super-span cut-and-cover tunnels in deep overburden soil.
The implications for the energy sector are profound. As we push the boundaries of infrastructure development, understanding the mechanical characteristics and unloading mechanisms of deep, super-span tunnels becomes crucial. This research provides a robust framework for enhancing the safety and efficiency of large-scale tunneling projects, paving the way for more ambitious and sustainable energy infrastructure developments.
As the world continues to demand more from its energy sector, innovations like these will be key to meeting those demands safely and efficiently. The study by HUANG Jixin and his team is a testament to the power of innovative thinking and rigorous research in driving progress in the construction industry.