Study on the Mechanism of Tunnel Subhorizontal Jet Grouting Reinforcement Based on a Shell Model on Two-Parameter Foundation

Horizontal jet grouting columns (HJGCs) are commonly adopted to reinforce weak ground ahead of the tunnel excavation face. However, the dynamic mechanical response of the HJGCs during tunneling remains unclear. To provide a comprehensive understanding of HJGC reinforcement mechanisms and a basis for optimal design, a mechanical shell model for the HJGCs based on the two-parameter Pasternak foundation is initially established, and the analytical solutions for deflection and internal force are derived. Furthermore, the feasibility of the proposed model is validated through comparisons with numerical simulations based on an actual project. Subsequently, the mechanical behavior of the HJGCs and the sensitivity of the design parameters on the HJGCs deformation are examined. Additionally, the influence of various factors on tunnel face stability is deliberated. The findings suggest that the analytical solution derived from the proposed model aligns closely with the results obtained through numerical simulation. The longitudinal deflection pattern of the HJGCs is categorized into the airside impact zone, excavation disturbance zone, and forward stability zone. Significantly, the transverse deflection at the vault exhibits the greatest magnitude and gradually diminishes toward the arch foot. Longitudinally, the HJGCs reinforcement effectively serves as a spatial leverage mechanism, facilitating the redistribution of pressure within the spatial domain. In addition, the sequence of the impact levels of the discussed parameters or factors is presented individually.