端锚锚杆工作载荷的导波确定法

 使用纵向导波对端锚锚杆的工作载荷进行无损检测。首先分析端锚锚杆工作载荷在锚杆自由段及锚固段的不同分布特征，然后计算纵向导波在锚杆自由段(承受拉应力)中的传播速度。当锚杆变形在弹性范围内时，随着自由段承受拉应力的增大，同一频率纵向导波在锚杆中传播的群速度逐渐减小，并且群速度与拉应力大小呈线性递减关系；对纵向导波在端锚锚杆锚固段上界面的反射情况进行试验研究，结果表明，45～75 kHz频率范围纵向导波在锚固段上界面有明显的反射回波；提出使用纵向导波在锚固段上界面的反射回波及在锚杆自由段的传播时间来确定锚杆工作载荷的大小，由理论分析得到的工作载荷与导波传播时间的关系曲线与试验结果具有相同的趋势。

GUIDED WAVE DETERMINATION METHOD OF SERVICE LOAD IN PARTIALLY GROUTED BOLT

Longitudinal guided wave is used to inspect the service load in the partially grouted bolt nondestructively. The stress distribution characteristics of free section and anchoring section in the partially grouted bolt under service load was first analyzed and tensile stress keeps constant in the free section of the bolt. Then group velocity of longitudinal guided wave propagating in the free section of the bolt under different tensile stresses was calculated. The results show that the group velocity decreases linearly with the increase of tensile stress within the elastic distortion range. Experiments were conducted to study the reflection of longitudinal guided wave from the upper interface of anchoring section of partially grouted bolt；and it shows that the upper interface reflection wave can be observed clearly when the frequencies of guided wave are 45–75 kHz. The reflection of longitudinal guided wave from the upper interface of partially grouted bolt and the time of guided wave propagating in the free section of the bolt can be used to determine the service load in the partially grouted bolt；and the theoretical and experimental results of service load-propagation time have the same trend.