Analysis on deformation law of shallow buried and undercut loess stratum slow slope construction tunnel

Abstract By analyzing the stress and deformation patterns of shallow buried slow slope loess tunnels under lateral pressure, numerical analysis was conducted using finite element analysis software, and the simulation results were statistically compared with on‐site measurements. The results show that under the influence of lateral pressure, the stress changes in the steel arch support on the left side of the tunnel arch waist are relatively large. The maximum stress value at the left arch waist is ‐64.95MPa, followed by the crown at ‐36.46MPa, and the smallest at both arch feet, at ‐7.42MPa. The stress at the left arch waist is 8.75 times that at the arch feet. Therefore, it is advisable to appropriately increase the parameters of the advanced support on the side affected by lateral pressure. The surface settlement of the tunnel decreases gradually from the centerline of the tunnel towards both sides; during the tunnel excavation period, the settlement at the crown is relatively large, with the maximum daily settlement reaching 16.89mm/d, and the average settlement is about 2‐5mm/d; the net horizontal convergence deformation is relatively stable, with an average convergence deformation rate of 1.6‐3.9mm/d, without significant fluctuations. Therefore, when excavating tunnels in the loess plateau area, the initial support should be closed in a timely manner to form a ring to reduce deformation.