An innovative shape memory alloy flexible circumferential joint for tunnel seismic mitigation

Abstract

Under strong ground motion, shield tunnels passing through uneven soil layers are easily damaged. Based on the concept of elastic washers, a shape memory alloy (SMA) flexible circumferential joint for longitudinal seismic mitigation of shield tunnels is proposed to achieve seismic mitigation with minimal impact; it is composed of SMA ring springs and ordinary joint bolts. The test performance and influencing factors of SMA ring springs are discussed. Then, based on the analytical solution of the SMA ring spring, the design method of the SMA flexible circumferential joint is proposed. The mechanical properties of the SMA flexible circumferential joint under different loads are studied through the numerical simulation of tunnel joints. Test, analysis and simulation results indicate that SMA ring springs have good energy dissipation and self-recovery effects and can satisfy the mechanical performance requirements of elastic washers. The joint design method can conveniently and efficiently design suitable SMA flexible circumferential joint. Numerical simulations show that under various loads, the joints can reduce the longitudinal stiffness of the tunnel and dissipate energy. The joint can improve the ability of the tunnel to adapt to the soil deformation under earthquakes, reduce the internal force of the structure and at the same time achieve energy dissipation effect, thereby enhancing the seismic safety of the tunnel.