A THEORETICAL FRAMEWORK FOR DETECTING AND MONITORING GROUND FISSURES USING DISTRIBUTED FIBER OPTIC SENSING

The detection and monitoring of ground fissures is vital to understand their mechanism and the prevention and control of related hazards. Recently, high-and ultra-high-resolution distributed fiber optic sensing(DFOS) techniques have been developed and applied in the field of geoengineering. This provides a technological basis for improved detection and monitoring of ground fissures. This paper discusses a theoretical framework for ground fissure detection and sensing using the DFOS technique. Based on the tensile failure mode of soil during ground fissure formation and by considering that DFOS captures linear strains, a strain-based failure criterion is proposed as follows:R_s=ε₃/ε_t, where ε_t is the ultimate tensile strain of soil and ε₃ is the minimum principal strain. A value of R_s larger than 1 means that the absolute value of the minimum principal stress has exceeded the ultimate tensile strain of soil. Hence, tensile failure may occur. The ground fissure monitoring results are influenced by a combined effect of spatial resolution, fiber optic cable-soil interaction, strain localization, temperature variation, and strain transfer efficiency. These effects and their countermeasures are also analyzed and discussed. To improve the quality of DFOS-based monitoring, these effects should be carefully addressed according to different geologic conditions and monitoring schemes.