Investigating the hydro-mechanical properties of calcareous sand foundations using distributed fiber optic sensing

In this study, a model test was carried out to investigate the hydro-mechanical properties of calcareous sand, and distributed fiber optic sensing technologies were utilized to monitor the entire process. The test procedure had three stages: one-way water supply, one-way drainage, and two-way drainage. The actively heated fiber optic (AHFO) method was used to monitor the soil moisture profiles, and soil deformation was captured using the high-accuracy optical frequency domain reflectometry technique. The Pearson correlation function was used to describe the relationship between soil compression and moisture content. The results indicated that the AHFO method allowed soil moisture measurement in saturated and unsaturated zones with a bias of 0.027 m(3)/m(3). Water infiltration in calcareous sand can lead to uneven settlement, toppling, and horizontal deformation, with most settlements occurring during the watering stage. The ground settlement was mainly caused by particle sliding and rotation during the watering and drainage processes. The results show that settlement occurred earlier when the soil was closer to the water supply chamber. Moreover, tension cracks can easily appear between the calcareous sand and fine-grained soil interlayers. The Pearson correlation coefficients were larger than 0.8, indicating that the soil layer was compressed owing to particle sliding and rotation, and the moisture contents had a linear correlation with compressive strains.