Research on stability of tunnel surrounding rock is very important to the safety construction and operation of tunnel.The method of site monitoring is the most intuitive method to judge the stability of tunnel surrounding rock.Based on the Yuanbazi Tunnel as the engineering background,through on-site monitoring system of Ⅲ,Ⅳ,Ⅴ different grades of surrounding rock after initial support of the crown settlement and the surrounding convergence test,rock stability research under complicated geological conditions,the results show that the stability period of tunnel vault and surrounding displacement is 10 ～15 d.The cumulative increase of total settlement amount and the surrounding convergence with the rock grade but a significant increase,but are in the allowed range,which shows tunnel excavation methods and supporting scheme is scientific and reasonable.The research results can provide reference for the design,construction and monitoring of tunnel engineering under similar conditions.%隧道围岩稳定性分析对隧道安全施工和运营至关重要,采用现场监测方法是判定隧道围岩稳定性最直观的一种方法.以原坝子隧道为工程背景,通过对Ⅲ、Ⅳ、Ⅴ不同等级围岩初期支护后拱顶下沉和周边收敛进行系统的现场监控量测,研究复杂地质条件下大断面隧道围岩的稳定性,结果表明,隧道拱顶及周边位移一般稳定期为10 ～ 15 d,累计沉降量和周边累计收敛量随围岩等级的增大而显著增大,并处于允许范围以内,说明隧道开挖方式和支护方案是科学合理的.研究成果可为类似条件下隧道工程的设计、施工、监测提供参考和借鉴.
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