提出一种利用光纤布拉格光栅(FBG)测试双壁模型管桩桩身轴力的方法,探讨模型管桩应变变化与光纤光栅中心波长稳定性和漂移的关系。FBG传感器封装在模型管桩外管加工槽体内,模型管桩内管采取直接粘贴光纤光栅的方法,将应变片分别粘贴在模型管桩内、外管光纤光栅同一位置。对模型管桩施加竖向压力后产生的应变进行测试,并将FBG传感器及应变片的测试结果与理论公式进行对比分析,发现两者存在误差,但在测试要求范围内。外管施加5 kN竖向荷载时,光纤光栅测得的最大应变为59.2 με,相对误差为4.9%;内管施加5 kN竖向荷载时,光纤光栅测得的最大应变为122.3 με,相对误差为7.2%,均满足工程测试要求。

The detecting method of measuring axial force of double-walled model pipe pile by fiber Bragg grating (FBG) is proposed. The relationship between the strain change of the model pipe pile and the stability and drift of the central wavelength of the fiber grating is discussed. FBG sensor is packaged in the external tube of the mode pipe pile, and is attached on the internal tube of the mode pipe pile. The strain gauges are stuck on the same position of fiber grating of external tube and internal tube of mode pipe pile, respectively. After the vertical stress is exerted on the model pipe pile, the strain of the model pipe pile is tested, and the test results of the FBG sensor and the strain gauge are compared with the theoretical formula. It is found that there are errors between them, but within test requirements. When the vertical load of 5 kN is applied to the external tube, the maximum strain measured by the FBG is 59.2 με and the relative error is 4.9%. The maximum strain of internal tube measured by the FBG is 122.3 με with a relative load of 5 kN, and the relative error is 7.2%. These errors are allowed for the engineering test requirements.