一维弹性杆波动理论地铁隧道锚杆无损检测试验研究

Research on nondestructive testing of metro tunnel anchor rod based on one-dimensional elastic rod wave theory

针对地铁隧道锚杆无损检测问题研究的不足,以青岛地铁隧道锚杆为研究对象,应力波在一维弹性杆中的传导为理论基础,首先利用ansys/ls-dyna软件建立锚杆锚固三维模型,分析锚固长度和锚固缺陷对应力波反射信号的影响,然后通过理想模型对比试验的方法,制作物理模型并对采集到的结果进行分析,试验数据验证数值模拟的准确性。结果证明:室内试验中基于一维弹性杆波动理论的应力波反射法对于4~5 m的地铁隧道锚杆长度和缺陷位置检测结果准确率可达95%以上;当缺陷位置距锚固底端小于1 m时,会对底端回波产生干扰,影响对缺陷长度的准确判定,同时也会降低对锚固底端判定的准确率;室内模型中设置的锚后段会对应力波反射信号产生影响,在工程实际中需要注意锚杆后部水泥砂浆和围岩的影响。

Aiming at the deficiencies of the research on the non-destructive testing of metro tunnel anchor rods,the Qingdao metro tunnel anchor rod is taken as the research object,and the stress wave conduction in the onedimensional elastic rod is the theoretical basis.First,use ansys/ls-dyna software to establish a threedimensional anchor bolt anchoring model,analyze the impact of anchoring length and anchoring defects on the stress wave reflection signal,and then make a physical model and analyze the collected results through the method of ideal model comparison test,the test data verifies the accuracy of the numerical simulation.The results prove that the accuracy of the stress wave reflection method based on the one-dimensional elastic rod wave theory in the indoor test for the length of the anchor rod and the defect position of the subway tunnel of 4-5 m can reach more than 95%;When the defect position is less than 1 m from the anchoring bottom end,it will interfere with the bottom echo,which will affect the accurate judgment of the length of the defect,and also reduce the accuracy of the anchoring bottom end;The back section of the anchor set in the indoor model will affect the stress wave reflection signal.In engineering practice,attention should be paid to the impact of cement mortar and surrounding rock behind the anchor rod.