超大断面隧道（断面面积大于100 m²）开挖面积大，围岩扰动性强，因此常常需要进行超前支护控制隧道施工安全，管棚注浆加固是一种常见的隧道超前支护方式，其主要通过在隧道围岩上方形成注浆加固圈从而控制围岩应力和变形大小。在进行数值模拟计算过程中，注浆加固圈厚度是计算结果准确的关键。依托渝黔铁路张家山隧道工程，考虑管棚外插角和搭接长度对注浆加固圈厚度的影响，对传统计算公式进行优化，采用FLAC3D对比分析未使用管棚注浆加固和使用管棚注浆加固两种计算工况。结果表明：①优化后的注浆加固圈厚度计算公式与管棚外插角、浆液扩散半径、管棚长度、管棚纵向间距和环向间距5个参数相关，且使用优化后计算公式得到的数值模拟结果与现场监测数据更接近，计算结果更准确；②相较于未使用超前管棚注浆支护，使用超前管棚注浆支护拱顶沉降位移为12.65 mm，减小31.06%；③管棚注浆支护能够降低围岩竖向最大压应力20.72%和最大竖向拉应力44.68%，同时能够降低初期支护结构最大主压应力15.87%和最大主拉应力23.81%；④管棚注浆加固的地表沉降最大值为8.95 mm，较未使用管棚注浆加固减少24.25%；⑤管棚注浆加固效果与浆液扩散半径、管棚外插角和管棚长度呈正相关，与管棚纵向间距和环向间距呈负相关，其中浆液扩散半径影响效果最显著，管棚外插角影响最小。

The excavation area of super-large section tunnels (with a cross-sectional area greater than 100 m²) is large, leading to significant disturbance of the surrounding rock. As a result, advanced support is often required to ensure the safety of tunnel construction. Pipe shed grouting reinforcement is a widely adopted method for advanced tunnel support, primarily aimed at controlling the stress and deformation of the surrounding rock by creating a grouting reinforcement ring above the tunnel's surrounding rock. In numerical simulation calculations, the thickness of the grouting reinforcement ring plays a critical role in the accuracy of the results. An optimization of the traditional calculation formula was proposed, considering the impact of the pipe roof extrapolation angle and lap length on the thickness of the grouting reinforcement ring, based on a practical tunnel project. FLAC3D was employed to perform a comparative analysis between two calculation conditions: grouting reinforcement with and without a pipe roof. The results show the following.① The optimized formula for determining the thickness of the grouting reinforcement ring is influenced by five parameters: the pipe roof extrapolation angle, grouting diffusion radius, pipe roof length, longitudinal spacing, and circumferential spacing of the pipe roof. Numerical simulations based on the optimized formula yield results that are more consistent with field monitoring data, thereby improving the accuracy of the calculations. ② When advanced pipe shed grouting support is applied, the settlement displacement at the tunnel vault is reduced to 12.65 mm, representing a decrease of 31.06% compared to the condition without advanced support. ③ The pipe roof grouting support leads to a reduction of 20.72% in the maximum vertical compressive stress of the surrounding rock, a reduction of 44.68% in the maximum vertical tensile stress, a 15.87% decrease in the maximum principal compressive stress of the initial support structure, and a 23.81% reduction in the maximum principal tensile stress. ④The maximum surface settlement with pipe shed grouting reinforcement is found to be 8.95 mm, which is 24.25% lower than that observed in the absence of such reinforcement. ⑤ The grouting reinforcement effect of the pipe shed is positively correlated with the slurry diffusion radius, the outer angle of the pipe shed, and the length of the pipe shed, while it is negatively correlated with the longitudinal spacing and circumferential spacing of the pipe shed. Among these parameters, the slurry diffusion radius exerts the most significant influence, whereas the outer angle of the pipe shed has the least effect.