锚头的受力情况对整个锚杆的安全性有着重要影响。为了实时反映锚头的受力状态, 将2只光纤Bragg光栅沿45°粘贴在轮辐式结构锚头的两根对称辐条中点处表面上, 形成轮辐式测力传感结构, 辐条在压力作用下产生剪切变形, 引起辐条表面的光纤Bragg光栅中心波长移位。通过对光纤Bragg光栅中心波长移位的测量, 实现在锚头处锚杆轴向拉力的在线监测。锚头压力实验表明: 光栅1的测力灵敏度为108.8pm/kN, 线性度为0.042% FS; 光栅2的测力灵敏度为115pm/kN, 线性度为0.023% FS。

The force of the anchor head has a significant impact on the safety of the anchor rod. In order to reflect the force status of the anchor head on-line, the two optical fiber Bragg grating along 45 ° are pasted on the surface at the midpoint of the two symmetry spokes, forming the spoke-and-wheel structure. The stress of anchor causes the shear deformation of spokes, and the deformation leads to the wavelength-shift of fiber Bragg grating. By measuring the center wavelength-shift of fiber Bragg grating, axial force at the anchor head on-line is monitored. The press experiment shows that the strain sensitivity of grating 1 is 108.8pm/kN, grating 2 is 115pm/kN; Linearity of grating 1 is 0.042% FS, grating 2 is 0.023% FS.