大跨径铁路车站隧道施工力学特性研究

Study on Mechanical Performance for the Construction of a Large-span Railway Station Tunnel

依托大(理)丽(江)铁路三线大跨车站隧道工程,对隧道(出口端跨度大于20 m)洞口段(48 m)进行了施工过程的三维有限元数值分析。通过对隧道围岩应力与塑性区分布状态的分析得出:大跨隧道核心土底部和边墙两侧出现了应力集中区域,拱顶部位易出现拉应力;临时横撑滞后4个循环(即8 m)可发挥作用,能够有效控制围岩应力分布形态和塑性区的发展;大跨隧道核心土塑性区完全贯通,最大塑性区出现于隧道两侧边墙中部。根据数值分析结果,在隧道应力集中区域进行注浆加固和合理的分部开挖,并从现场监控量测结果反馈出隧道围岩压力及钢拱架内力变化较小,说明隧道加固措施能够有效控制塑性区范围和减弱围岩应力集中现象。

Considering the construction of Heluoshan large-span railway tunnel,three-dimensional numerical analysis was carried out for the 48-metre long tunnel entrance section during construction.By analyzing the plastic zones and surrounding rock stresses of the tunnel,it was found that the stress concentrations appeared at the bottom of core soil and on both sides of sidewalls,at the same time tensile stress appeared at the crown.Erecting of temporary lateral braces lagged behind 4 cycles（8 meters） could effectively control the distribution of rock stresses and the development of the plastic zones.Plastic zones of core soil were completely connected together in the tunnel and the largest plastic zones appeared at the middle of both side-walls.Based on the results of numerical analysis,grouting and reasonable excavation by parts were adopted in stress concentration regions.Feedback results of in-situ measurement indicated,that changes in surrounding rock pressures and the internal forces of Isteel ribs were smaller,thus the reinforcement measures were effective to control the plastic zones and to alleviate the stress concentration in surrounding rocks.