Influence of Thickness of the Partition Wall on the Bearing Capacity of Double-Arch Tunnel Under Different Buried Depth

The double-arch tunnel has been widely used in traffic engineering. As a key parameter of the partition wall, its thickness is closely related to the wall's bearing capacity. In this study, we use a double-arch tunnel passing through pulverized coal ash as an example and establish a numerical simulation model to study how the partition wall's thickness influences the tunnel's bearing capacity. The results show that the presence of the partition wall can significantly improve the stress state of the tunnel, meanwhile, excessive thickness of the middle partition wall can cause an increase of the arch crown stress. Compared to tunnels without a partition wall, when the thickness of the partition wall increases to 0.025 D, the arch load will increase by more than 30%. Furthermore, the results indicate that the bearing capacity is strongest when the thickness of the partition wall d is 0.0625 D. For tunnels without a partition wall, tensile stress concentration at the junction of the left and right holes will easily lead to cracking, and the right sidewall of the left hole will become the main compression part in the subsequent loading, resulting in complex tensile-compression-shear failure. For double-arch tunnels with a partition wall, the spandrel and the wall footing of the sidewall are the weak points of stress and are prone to damage, so these parts should be strengthened appropriately in design and construction.