浅埋富水软弱围岩隧道支护受力特征及方案研究

Study on support mechanical behaviour and scheme for shallow buried tunnel in weak surrounding rock with rich water

依托关角隧道河谷浅埋段,展开富水软弱围岩隧道支护受力特征及方案的研究。对试验段的初支围岩压力、钢架应力、锚杆轴力、衬砌水压力进行现场监测,结果表明:初支应力不能得到有效控制、突水突泥塌方现象时有发生,现有的支护方案无法满足浅埋段安全施工要求。在监测数据基础上,经过综合分析,对支护方案作出调整。在Ⅴ级围岩区段,拱部120°范围设超前管棚和小导管,宽大节理掌子面超前小导管注浆加固,初期支护取消系统锚杆,采用I20型钢钢架和拱墙设双层钢筋网;在Ⅵ级围岩区段,超前支护采用管棚工作室施作拱部180°及以下1 m范围的0°角长管棚,全断面超前水平钻孔注浆,初期支护取消系统锚杆,采用I20型钢钢架、三台阶型钢临时横撑和双层防水板。研究成果可为河谷浅埋隧道支护方案的确定提供理论依据和基础数据,为同类工程的设计与施工决策提供借鉴。

Shallow buried section under river valley of Guanjiao tunnel has been done a series of research on support mechanical behaviour and scheme for tunnel in weak surrounding rock with rich water.Pressure of surrounding rock,stress in the steel frames,axial force of rock bolts and water pressure on lining are obtained by monitoring in test section.The result indicates that primary support can＇t be effectively controlled,inrush of clay and water and collapse occour sometimes,and the present support scheme can＇t meet the safe construction requirements.By a comprehensive analysis of monitoring data,adjustment to support scheme is made.In Ⅴ class surrounding rock section,lead pipe-shed and small pipe is set in the range of120° at arch part;grouting reinforcement with small pipe is conducted in wide joints of driving face.Five meters grouted rock bolts,I20 steel frames and double layer mesh at arch wall constitute the primary support.In Ⅵ class surrounding rock section,0° lead pipe-shed set with pipe shed workroom in the range of 180° at arch part and 1 m below and whole section advance level drilling grouting are the main measures of advance support;7.5 m self-drilling bolt,I20 steel frames,steel temporary support and double waterproof board constitute the primary support.These research results can provide theoretical basis and underlying data for support scheme for shallow buried tunnel under river valley,and have high referential value for design and construction decision-making of analogous project.