Research on subway shield tunnel induced by local water immersion of collapsible loess

There are an increasing number of cases wherein the soil around a tunnel is immersed in water, which adversely affects the tunnel. To study the influence mechanism of local immersion of loess stratum on metro shield tunnel in detail, a similarity model test and numerical simulation were used in this study. These were used to investigate the stress and deformation of tunnel lining and stratum and surface settlement after a local soil collapse in the tunnel, and the mechanical mechanism that causes this effect. Further, the influences of different methods of water immersion on the tunnel lining were studied using numerical simulation. The results showed that the larger the collapsing area, the larger the bending moment and the axial force increment of the tunnel lining and the surface settlement; the bending moment and axial force near the side of the collapsing area were larger than those of the non-wet side. Vertical stress in the collapsible area was reduced, while the vertical stress of the non-collapsible soil on both sides of the collapsible area was increased due to the transmission of stress. When the water immersion area was the same, different water immersion methods also made the internal force of the tunnel lining slightly different; however, the difference was not obvious.