大断面小净距大帽山隧道现场监控量测及分析

On-site supervision measure and analysis of Damaoshan tunnels with large section and small clear-distance

结合大帽山隧道的工程实践,通过围岩内部位移、拱顶沉降、围岩压力和锚杆应力的现场监控量测工作,研究复杂地质条件下大断面小净距隧道双侧壁导坑法施工时围岩的稳定性。阐明分导洞开挖时围岩内部位移的变化趋势、特点及位移场,相邻导洞施工时的相互影响,围岩与支护结构间的相互调整变形机制,拱顶沉降捕捉的变形小于围岩实际变形的原因,支护结构的压力和锚杆应力状态及其与围岩位移的变化关系。监测结果表明,大断面小净距隧道Ⅴ级围岩段的破碎带采用现有的施工工艺和支护参数是可行的,围岩变形可控,支护结构的支护效果显著,围岩基本稳定。研究的方法、分析和结论可为类似条件下隧道工程的设计、施工、监测和进一步的理论研究提供参考和借鉴。

The research on the stability of surrounding rock is carried out during the construction, as per twin-side heading method, of large section and small clear-distance tunnels under complex geological condition; through the on-site supervision measure of internal displacements of surrounding rock, vault settlement, pressure of surrounding rock and stress of bolt in combination with the engineering practice of Damaoshan tunnels. When the pilot tunnels start excavating, the variation trend, characteristics and displacement field of displacement inside surrounding rock should be clarified, as well as the mutual influence of neighboring pilot tunnels in construction, mutual adjusting mechanism between surrounding rock and retaining structure and the reason of smaller distortion measured by vault settlement than the actual distortion of surrounding rock, the stress state of retaining structure, stress of bolt, variation relation of surrounding rock displacement. The supervision results indicate the feasibility of existing construction technology and retaining parameter adopted for fault zone of V-grade surrounding rock section of large section and small clear distance tunnels because of controllable surrounding rock distortion, strong retaining structure, safe storage and stable surrounding rock. The method, analysis and conclusion of research will be valuable experience and for reference in design, construction, supervision and further theoretical research on tunnel engineering under similar condition.