软岩深基坑锚杆预应力变化规律研究

Research on Prestress Variation Law of Anchor Bolt in Soft Rock Deep Foundation Pit

随着城市地下空间快速发展,预应力锚杆已作为主动支护结构在基坑边坡支护工程中广泛使用,但针对锚杆锚固后短期及长期预应力变化规律仍认识不足,尤其是锚杆预应力沿程分布情况及其变化规律。为探究锚杆预应力损失规律,本文基于分布式光纤光栅传感技术对锚杆加载过程及锚固后预应力变化情况开展现场监测和试验研究,并对影响因素进行分析总结。结果表明:锚杆锚固后预应力短期内会急剧下降,这主要是锚具锚固和锚杆钢筋松弛所导致,短期预应力损失率可达20%;锚杆预应力沿程分布可根据其受力情况分为自由区、过渡区、锚固区三部分,并随时间增长锚杆预应力沿程分布会发生显著变化。

With the rapid development of urban underground space,prestressed anchor bolts had been widely used as active support structures in foundation pit slope support engineering.However,there is still a lack of understanding of the short-term and long-term changes after anchor anchoring,especially the prestress distribution along the course and its variation law.In order to explore the law of prestress in anchor bolt,in this paper,based on the distributed fiber Bragg grating sensing technology,the in-situ monitoring and experimental analysis of loading process and post-anchoring prestress change were carried out.Additionally,the influencing factors were analyzed and summarized.The results showed that the short-term prestress decreased sharply after anchoring,which was mainly caused by anchoring and relaxation of anchor bar.And loss rate of shortterm prestress could reach 20%.The distribution of anchor prestress can be divided into three parts:free section,transition section and anchorage section according to its stress conditions,and with the increase of time,the distribution of anchor prestress along the route would undergo significant changes.