Anti-dislocation performance of ECC-RC composite supporting structures of tunnels passing through active fault

In light of the substantial number of tunnel constructions crossing active fault zones, the anti-dislocation performance of existing structural systems still needs further enhancement. Utilizing the ultra-high toughness and high damage tolerance of ECC materials, combined with the conventional composite supporting structures (CCSSs), an novel ECC-RC composite supporting structures (ECSSs) has been proposed. By establishing a mechanical model for dislocation response that considers the interactions between the tunnel, fault, and surrounding rock, analyzes the fault dislocation response results of two structures under different fault dislocation patterns, fault displacement amounts, fault types, and rock mass qualities. It investigates the anti-dislocation performance of the ECSS from the perspectives of deformation adaptability, structural damage state, and energy dissipation. The extent of damage and distribution range of the tunnel structure is closely related to the fault dislocation pattern. Under reverse fault, the structure exhibits compressive-shear failure, under normal fault, it exhibits tensile-shear failure, under strike-slip fault, it exhibits shear failure. Under reverse fault, the ultimate displacement of the ECSS structure is improved by 54.1–62.7 % compared to the CCSS. Under normal fault, the ultimate displacement of the ECSS is enhanced by 64.9–69.3 % compared to the CCSS. At a basic seismic fortification intensity level, the distribution range of tensile and compressive damage at typical characteristic locations of the ECSS is reduced by 28–52 % and 31–67 %, respectively, compared to the CCSS, with peak tensile and compressive damage decreasing by 24–28 % and 23–25 %, respectively, and energy dissipation ratio decreasing by 7.1–23.9 %. In regions with lower surrounding rock stiffness or where the rock mass quality is relatively similar (having good continuity), the damage degree and extent of the ECSS are smaller, and the enhancement in ultimate offset is more pronounced. • An novel ECC-RC composite supporting structures (ECSSs) has been proposed. • The fault dislocation response of ECSS and CCSS were discussed. • The anti-dislocation performance of ECSS and CCSS were investigated. • The ECSS obviously improved the anti-dislocation performance of tunnels.