基于3DEC的浅埋隧洞失稳过程分析及支护设计

Instability Process Analysis and Support Design of Shallow Buried Tunnel Based on 3DEC

针对浅埋破碎围岩隧洞开挖,确定围岩的稳定性对于隧洞的安全施工意义重大。依托小浪底北岸灌区工程,基于3DEC离散元软件模拟节理破碎岩体隧洞开挖过程,计算隧洞拱顶块体的位移、应力状态,研究关键块体失稳引发隧洞坍塌连锁反应,分析块体节理强度对围岩稳定的影响,最后模拟分析超前支护措施对隧洞整体稳定的影响。模拟结果表明,开挖过程中拱顶块体发生明显失稳,进而引发围岩整体坍塌,并可由此分析块体失稳的先后顺序;增加围岩节理面强度可显著提高围岩自稳能力;增加围岩支护措施后,最大地面沉降位移为0.9 cm,与现场监测结果接近。

It is of great significance to determine the stability of surrounding rock for the excavation of shallow broken surrounding rock tunnel.Based on Xiaolangdi North Bank Irrigation Area project,3DEC discrete element software was used to simulate tunnel excavation process of jointed broken rock mass and calculate the displacement and stress state of tunnel arch block.The chain reaction of tunnel collapse caused by the instability of key block was studied.The influence of block joint strength on the stability of surrounding rock was analyzed.Finally,the influence of advance support measures on the overall stability of tunnel was simulated.The results show that the arch block is obviously unstable during excavation,which leads to the whole surrounding rock collapse,and the sequence of block instability is analyzed.Increasing the strength of joint surface of surrounding rock can significantly improve the self-stability of surrounding rock.After adding surrounding rock support measures,the maximum ground subsidence displacement is 0.9 cm,which is close to the field monitoring result.