In the heart of Chongqing, a city known for its dramatic landscapes and ambitious infrastructure projects, researchers are redefining the future of tunnel construction. Led by Zhanglong Xu of the State Key Laboratory of Mountain Bridge and Tunnel Engineering at Chongqing Jiaotong University, a groundbreaking study on composite wet joints in large-span open-cut tunnels is set to revolutionize the industry.
The Chongqing Xinsen Avenue Tunnel, an eight-lane highway tunnel, serves as the backdrop for this innovative research. The team proposed a novel inverted-T composite wet joint design, aiming to streamline construction and enhance structural performance. “Our goal was to create a joint that could withstand the immense forces and pressures exerted on large-span tunnels while simplifying the construction process,” Xu explained.
To achieve this, the researchers conducted full-scale laboratory bending tests on the joint under varying axial loads and reinforcement lap lengths. They characterized the joint’s load-bearing capacity, stiffness, and failure modes, providing invaluable data for future designs. The results showed that the composite joint typically fails in a highly eccentric compression-bending mode, a critical insight for engineers.
But the team didn’t stop there. They developed a detailed finite-element model using the Concrete Damaged Plasticity (CDP) approach, calibrated against the test results. This model allowed them to perform parametric analyses of key design variables, offering a deeper understanding of the joint’s behavior under different conditions.
One of the most compelling findings was that increasing the reinforcement lap length yields only limited improvement in flexural capacity. “This was a surprising discovery,” Xu admitted. “It challenges conventional wisdom and suggests that we need to rethink our approach to reinforcement in these structures.”
The researchers also developed a three-dimensional soil–structure interaction model of a complete tunnel ring to simulate the staged construction process. This model captured the evolution of internal forces, deformations, and failure mechanisms, providing a comprehensive picture of the tunnel’s behavior over time.
The full-ring analysis revealed that under staged loading, the lining transitions from elastic behavior to a four-hinge mechanism. Controlling crown settlement within prescribed limits is critical for serviceability, a finding that could have significant implications for future tunnel projects.
This combined experimental and numerical study clarifies the mechanical behavior and failure mechanisms of inverted-T composite wet joints. The research, published in *Case Studies in Construction Materials* (translated as “典型建筑材料研究案例”), provides theoretical guidance for the design of such joints in large-span prefabricated arch tunnels.
The implications for the energy sector are substantial. As the demand for large-scale infrastructure projects continues to grow, so does the need for innovative solutions that can withstand the unique challenges posed by these structures. This research offers a promising path forward, one that could shape the future of tunnel construction and beyond.
As Xu put it, “Our findings not only advance our understanding of composite wet joints but also pave the way for more efficient and safer tunnel construction methods. We are excited to see how this research will influence the industry and contribute to the development of more resilient infrastructure.”