为探究水平旋喷拱棚缺陷对其预支护效果的影响，依托实际工程，设计缩尺模型试验，探究旋喷桩在不同桩芯咬合距下，拱棚变形以及地层沉降变化规律。运用PLAXIS 3D有限元软件模拟隧道开挖，探究桩体存在缺陷对拱棚变形趋势以及加固效果的影响。模型试验结果表明：拱棚桩芯咬合距越大，对应地表沉降和挠度越大，当咬合距增大50%时，地表沉降和挠度分别增大22%和33%；数值分析结果表明：拱棚咬合面积降低和地层渗透系数增大均会使得掌子面挤出变形加剧，咬合面积下降至25%时，变形增大了78.77%，地下水会带动周遭土体从缺陷处渗入掌子面，此时拱棚在缺陷边缘处出现应力集中现象，最大压应力增大了110%，缺陷处最大主应力由压应力变为拉应力，预支护效果会大幅下降，因此在工程中成桩时需严格把控桩芯咬合质量。

In order to explore the influence of horizontal jet grouting arch shed defects on its pre-supporting effect, based on the actual project, a scale model test was designed to explore the deformation of arch shed and the change law of stratum settlement under different pile core occlusion distances. PLAXIS 3D finite element software was used to simulate tunnel excavation, and the influence of pile defects on the deformation trend and reinforcement effect of arch shed was explored. The model test results show that the larger the interlocking distance of the arch shed pile core, the larger the corresponding surface settlement and deflection. When the interlocking distance increases by 50%, the surface settlement and deflection increase by 22% and 33%, respectively. The numerical analysis results show that the decrease of the occlusal area of the arch shed and the increase of the permeability coefficient of the stratum will aggravate the extrusion deformation of the tunnel face. When the occlusal area decreases to 25%, the deformation increases by 78.77%. The groundwater will drive the surrounding soil to infiltrate into the tunnel face from the defect. At this time, the arch shed appears stress concentration at the edge of the defect, and the maximum compressive stress increases by 110%. The maximum principal stress at the defect changes from compressive stress to tensile stress, and the pre-support effect will be greatly reduced. Therefore, the quality of the pile core should be strictly controlled when the pile is formed in the project.