基于FLAC3D的隧洞循环进尺数值模拟分析

FLAC3D-Based Numerical Simulation Analysis of Tunnel Excavation Advance Rates

摘要: 为确定某抽水蓄能电站引水隧洞浅埋V级围岩段的合理开挖循环进尺，保障施工安全与效率，采用FLAC3D建立三维数值模型，模拟全断面法下1 m、1.5 m、2 m、2.5 m四种循环进尺的开挖过程，分析围岩位移、支护结构内力及塑性区分布特征。结果表明：随着循环进尺增大，拱顶沉降(6.1 mm→6.83 mm)和水平净空收敛(6.14 mm→6.94 mm)略有增加，但均满足允许值；支护结构内力(锚杆轴向应力、弯矩)显著增大，1.5 m进尺时锚杆轴向应力比1 m增大1.2倍，2 m时比1.5 m增大2.4倍，2.5 m时比2 m增大3.4倍，而1.5 m进尺时支护内力相对较小；1~2 m进尺时围岩塑性区未连贯成环，稳定性较好，2.5 m时塑性区略有扩展但仍可控。综合围岩稳定性与支护受力分析，全断面法循环进尺1.5 m为最经济合理的选择，既满足开挖稳定要求，又优化了支护内力分布，可为类似工程提供参考。

Abstract: To determine the reasonable excavation cycle advance rate for the shallow-buried Grade V surrounding rock section of a water diversion tunnel in a pumped-storage power station and ensure construction safety and efficiency, a 3D numerical model was established using FLAC3D. The model simulated the excavation process of the full-face method with four cycle advance rates (1 m, 1.5 m, 2 m, 2.5 m), and the characteristics of surrounding rock displacement, support structure internal force, and plastic zone distribution were analyzed. The results indicate that: with the increase of cycle advance rate, the vault settlement (6.1 mm to 6.83 mm) and horizontal clearance convergence (6.14 mm to 6.94 mm) increased slightly, but all remained within the allowable limits; the internal force of the support structure (axial stress of bolts, bending moment) increased significantly—compared to the 1 m advance rate, the axial stress of bolts at 1.5 m increased by 1.2 times; at 2 m, it was 2.4 times higher than that at 1.5 m; and at 2.5 m, it was 3.4 times higher than that at 2 m. However, the internal force of the support structure at 1.5 m advance rate was relatively small. For advance rates of 1~2 m, the plastic zone of the surrounding rock did not form a continuous ring, exhibiting good stability; at 2.5 m, the plastic zone expanded slightly but remained controllable. Comprehensively analyzing the surrounding rock stability and support force, the 1.5 m cycle advance rate of the full-face method is the most economical and reasonable choice. It not only meets the requirements of excavation stability but also optimizes the distribution of support internal force, providing a reference for similar projects.