In the heart of Yunnan, China, a monumental engineering challenge is being tackled with cutting-edge technology and innovative thinking. The Tabaiyi Tunnel, part of a larger infrastructure project, is proving to be one of the most complex tunnels ever attempted. The region’s geological complexity, characterized by tectonic dissolution, erosion, and a multitude of faults and fracture zones, has led to significant challenges in maintaining structural integrity. The tunnel’s surrounding rock, a mix of weathered metamorphic sandstone, schist, and slate, is particularly problematic due to its loose structure and high clay mineral content. This has resulted in large deformations, steel arch frame distortions, and sudden mud and water influxes, posing significant risks to the project’s safety and efficiency.
Jieli Li, a researcher from the Power Construction Corporation of China Road Bridge Group Co., Ltd., is at the forefront of this challenge. Li’s team has been investigating the deformation and damage mechanisms of the surrounding rock, utilizing a combination of field investigations, rock structure analysis, and numerical simulations. “The regional ground stress is mainly dominated by tectonic stress, and the groundwater in the tunnel site area is controlled by lithology, tectonics, topography, and geomorphology,” Li explains. This intricate interplay of factors has necessitated a sophisticated approach to managing the tunnel’s large deformations.
The team’s solution involves the implementation of an NPR anchor cable control system, which has shown remarkable effectiveness in controlling large deformations. The system has successfully limited the surrounding rock’s deformation to within 300 mm, a significant achievement given the challenging conditions. To further enhance the project’s safety and efficiency, Li’s team has optimized the design of the NPR anchor network and three-dimensional steel arch coupling support. This optimization process involved extensive numerical simulations using FLAC3D and PFC3D software, allowing the team to establish a robust support system that can withstand the tunnel’s dynamic conditions.
The field tests have yielded promising results, demonstrating the system’s ability to manage water-rich peripheral rock, mud, and local high-pressure water influxes. “The NPR anchor network and three-dimensional steel arch support system can solve the water-rich peripheral rock, mud, broken and local high-pressure water influx of engineering and technical problems,” Li asserts. This breakthrough has significant implications for the energy sector, where similar geological challenges are often encountered in tunneling projects for hydroelectric power, gas pipelines, and other critical infrastructure.
The research, published in ‘Meitan xuebao’ (translated to Coal Science and Technology), marks a significant advancement in the field of tunneling and large deformation control of soft rock. As the energy sector continues to expand and explore new frontiers, the insights gained from this research will be invaluable in shaping future developments. The ability to predict and manage large deformations in soft rock will not only enhance the safety and efficiency of tunneling projects but also pave the way for more ambitious and innovative infrastructure developments. The work of Jieli Li and her team serves as a testament to the power of interdisciplinary research and technological innovation in overcoming complex engineering challenges.
