Experimental Test of Ground Settlement Measurement Using Distributed Fiber Optic Sensing Technology

In foundation pit engineering, tunnel engineering, road construction and other engineering construction, measuring of settlement of ground surface is an essential operation. Compared with other measurement methods, distributed fiber optic sensing technology has intrinsic advantages such as high precision and low cost, making it an ideal method of ground settlement measurement that is widely used. However, there are a variety of distributed strain sensing (DSS) cable layout shapes, so it is important to select an appropriate cable layout shape for strain monitoring. By comparing the strain variations along DSS cables, the distinction between different cable layout shapes can be recognized. According to geometric principles, it is deduced that the strain variation of zigzag layout cables is more obvious than U-shape layout cable at the same deformation. To verify the feasibility of zigzag layout DSS cable measurement, a Brillouin optical time domain analysis (BOTDA)-based laboratory test was performed. The result showed that the relative error between calculated result and the measured displacements was in the range of 5%-20%, thus meeting the engineering monitoring requirements.