Evaluation of land subsidence potential by linking subsurface deformation to microstructure characteristics in Suzhou, China.

Land subsidence is often associated with compaction of subsurface strata, which cannot be recorded in detail by precise leveling, satellite imagery, and even extensometers. The distributed fiber optic sensing (DFOS) technique is advantageous in subsurface deformation monitoring, because it can image distributed profiles of vertical deformation by distributed strain sensing. Here, we propose to use the relationship between the soil porosity change and soil strain to verify the DFOS monitoring results. An observation case in Shengze, Suzhou (southern Yangtze Delta, China) 2012–2019 shows that compression strain occurs mainly in two aquitards adjacent to the pumping aquifer. The compression-rebound deformation of soil layers is closely related to the change in groundwater level. The microstructure, especially pore structure, affects the compressibility of soils. Changes in pore size derived by groundwater level fluctuations are macroscopically expressed as soil strain. The calculated strain induced by water level drop was basically consistent with the monitoring value, proving the credibility of DFOS technique. Moreover, DFOS can be used for the estimation of strata compression potential, which is of great significance to the management of land subsidence and groundwater exploitation. [ABSTRACT FROM AUTHOR]