Abstract:

Ground collapse poses a significant threat to urban safety, highlighting the need for effective field monitoring and early detection technologies. In this study, a trapdoor test was conducted to simulate ground-collapse formation. Optical frequency domain reflectometry (OFDR) and particle image velocimetry (PIV) were employed to analyze the strain responses of sensing optical fiber cables at different embedment depths and to investigate factors governing deformation coupling at the cable-soil interface. The results indicate that as the trapdoor descends, the cable strain curves exhibit a bimodal pattern, and the peak locations closely correspond to the shear-band propagation boundaries identified by PIV. The formation of stable soil arches can effectively suppress the propagation of failure surfaces and reduce the peak tensile strains measured by the cables. Increasing confining pressure and installing anchor plates can significantly enhance deformation compatibility at the cable-soil interface. However, if the anchor plate spacing is too small, overlapping soil shear zones may weaken the reinforcing effect of the anchor plates on cable-soil coupling. During collapse process, the anchor plates are significantly influenced by soil shear bands. Once the sensing cable enters an inclined tension state, the torque effect of the anchor plates increases significantly, causing them to rotate under lateral soil compression. The rotation center then gradually shifts toward the geometric center of the plates. This study provides a scientific basis for optimizing ground collapse monitoring schemes and offers references for research on collapse mechanisms and prevention practices.

Key words: fiber optic sensing, ground collapse, soil arch, anchored cable, interface coupling