Strain integration-based soil shear displacement measurement using high-resolution strain sensing technology

The distributed fiber optic sensing technology has emerged as a promising tool for monitoring soil shear deformation. However, the question remains whether the strain measurements obtained by the soil-embedded optical fiber cables are reliable due to cable-soil slippage. In this paper, a direct shear model test was conducted in laboratory to characterize the cable-soil deformation compatibility considering different anchorage conditions. The optical frequency domain reflectometer was employed to measure cable strains. The measurements were compared with those from the particle image velocity technique. When the strain sensing cable couples well with soil, the cable elongation exhibits a linear relationship with the soil shear displacement. A strain integration method is then proposed to convert strain measurements into shear displacements. Furthermore, the effect of block and tube anchors on the cable-soil coupling behavior is investigated. The conclusions drawn in this study provide a reference for establishing new geotechnical deformation monitoring systems. (C) 2020 Elsevier Ltd. All rights reserved.