In-situ Assessment of Curvature and Bending Characteristics Along Geotechnical Structures Using Distributed Fiber Optic Sensors

Abstract

Soil and rock mechanics applications require suitable monitoring concepts to assess the structure’s bearing capacity and the integrity of the structure itself. However, conventional monitoring methods mostly enable either only distributed measurements at the structures’ surface or pointwise measurements inside structures. This paper presents different case studies, in which distributed fiber optic sensors (DFOS) were used to capture strain profiles along grouted anchors, driven ductile piles as well as tunnel cross sections. As a result of the appropriate arrangement of two sensing layers along the monitoring objects, information orthogonal to the neutral axis of the sensing fiber, i.e. curvature and bending characteristics, can also be derived. The DFOS results are compared to conventional measurement techniques to examine the performance of the designed sensing approaches. Due to the distributed sensing feature and the high spatial resolution of about 10 mm, shape changes of embedded objects can be observed without gaps over the entire length, which gives new information about their structural behavior. This paper demonstrates the high potential of DFOS in geotechnical applications and the capability to extend conventional monitoring methods in soil and rock mechanics.