水电站地下厂房洞室顶拱的形成与锚固

FORMATION OF ARCH AND ROCKBOLTING OF UNDERGROUND POWERHOUSE ROOFS

在水电站地下洞室顶锚固设计中,认识岩石顶拱的形成与结构特征,又了解锚固的增强效果十分重要。应用古典楔块拱理论分析了地下洞室顶拱形成和拱的作用,根据极限平衡分析对顶拱锚杆加固进行了评价,并以小浪底工程地下厂房洞顶为例进行了分析,结合数值模型,针对锚杆和锚索对顶拱加固的不同效果进行了比较论证。结果表明:地下厂房洞顶自然拱结构在开挖后基本形成;系统灌浆锚杆加固是必要的;整个洞顶安装系统张拉锚索应谨慎,因其对顶拱稳定作用不大,且可能有负面影响。在水电站地下洞室顶锚固设计中,认识岩石顶拱的形成与结构特征,又了解锚固的增强效果十分重要。应用古典楔块拱理论分析了地下洞室顶拱形成和拱的作用,根据极限平衡分析对顶拱锚杆加固进行了评价,并以小浪底工程地下厂房洞顶为例进行了分析,结合数值模型,针对锚杆和锚索对顶拱加固的不同效果进行了比较论证。结果表明:地下厂房洞顶自然拱结构在开挖后基本形成;系统灌浆锚杆加固是必要的;整个洞顶安装系统张拉锚索应谨慎,因其对顶拱稳定作用不大,且可能有负面影响。

For supporting roof of underground powerhouse,a proper design of rock bolts should be based on a clear understanding of both formation and characteristics of the rock roof arch structure and the effect of rock bolt reinforcement. For this purpose,the mechanism of a rock cavern roof arch is studied and effects of different types of rock bolts are evaluated. Numerical modelling of rock bolt support of the Xiaolangdi powerhouse cavern is carried out and applications of arching theory are studied with the purpose to look into the effects of fully grouted rock bolts and tensioned cable anchors in reinforcing the cavern roof. It is concluded that a stable roof arch may be formed after excavation,systematic fully-grouted rock bolting is necessary in reinforcing the roof arch. However, the systematic tensioned cables should be used with caution since they may not be efficient after bolting,and further,they may create upward force to the arch,which counteracts the arch forming and possibly causes instability problems.