差动式光纤Bragg光栅沉降仪

研制了一种测量地表沉降变形的差动式光纤Bragg光栅沉降仪。等强度悬臂梁的底部固定于工地上的固定平台,顶端通过刃口、挂钩和连杆与沉降墩连接。在该测量中,沉降仪将沉降墩的地沉降量转换为悬臂梁的挠度。悬臂梁作用粘贴于其上下表面的光纤Bragg光栅产生应变,即传感光栅的Bragg波长产生了移位。对粘贴在悬臂梁上、下表面的传感光栅的Bragg波长进行差动运算,实现温度补偿,减小人为和气候因素的影响。在挂钩和沉降敦之间采用了螺旋结构连接,可通过调整螺旋或更换不同长度的挂钩来调节传感器的测量范围。荷载实验表明,该沉降仪的测量精度为0.004mm,低于变形测量中的科研级测量精度0.01~0.05mm。

A differential fiber Bragg grating settlement gauge

A differential fiber Bragg grating settlement gauge is developed.The bottom of a triangle cantilever beam of constant bending rigidity is fixed on the unyielding support of work site.The top is jointed to settlement pier via blade,pothook,and screw.In this scheme,the settlement gauge translates the displacement of the settlement pier into the deflection of the beam.The cantilever causes the strain of the fiber Bragg gratings mounted on the surface of the cantilever,i.e.,the Bragg wavelengths of sensing grating are shifted.Through the differential operation between the Bragg wavelengths of sensing grating mounted the up and down surfaces of the beam,the result achieves the temperature-compensated and reduces the effect of the artificial causation and the weather.The screw is connected between the pothook and the settlement pier,where the range can be adjusted by fine-tuning the screw and instead the pothook with the different length.The loading experiment indicates that the measure accuracy is 0.004 mm,which is less than the scientific-grade accuracy of 0.01～0.05 mm.