锚杆锚固质量电磁法检测的理论研究

Theoretical research on electromagnetic method for nondestructive detection of anchor bolts′ anchoring quality

近年来,锚杆锚固技术正在世界各地的隧道、采掘、高边坡和深基坑等工程支护中得到广泛应用。目前锚杆锚固质量的研究主要集中在以应力波法为主的无损检测方法,但该方法还要进一步研究以解决应力波信号变弱甚至消失的问题。电磁法是另外一种新的无损检测方法。对工程锚杆加载恒定电流时建立物理模型,通过电像法、欧姆定律和安培环路定理计算出了通电锚杆以及出现空锚时通电锚杆周围的电流和电磁场分布,得到了锚杆长度及锚固质量状况与检测磁场间的函数关系式。据此数值模拟出了几组相对磁感应强度曲线,进一步提出,对磁感应强度归一化曲线进行计算机拟合反演,可望检测出空锚段比例和空锚段的位置,从而为电磁法检测锚固质量提供了理论依据。

In recent years,anchor bolts have been widely used in supporting engineering in many areas,such as tunneling,mining,high slope and deep foundation pits,etc.Now the research of detection of anchor bolts focused on nondestructive testing is mainly about stress wave method.However,this method should be further studied to avoid signal weakening and disappearance of stress wave during its propagation.Electromagnetic method is a new nondestructive detecting method.We establish a physical model for anchor bolts which is loaded with constant electric current,and deduce the formulas of electric current density distribution and electromagnetic field in surrounding area of anchor bolt and in the area without anchor bolt by electric imagine method,Ohm law,and Ampere return circuit theorem;obtain the function relation between the magnetic field and the length as well as quality of the bolts.According to the above results,a group of relative curves of magnetic induction intensity is numerically simulated,and it is pointed out that through fitting normalized curves of magnetic induction intensity by computer,the proportion and location of the area without anchor bolt can be detected.The research provides a new nondestructive method for the quality check of bolt anchoring.