District-scale numerical analysis of settlements related to groundwater lowering in variable soil conditions

Abstract

This study presents a novel framework in which numerical modelling contributes to the performance of district-scale subsidence-induced damage assessment in cities where ground settlements affect entire quarters. Therein, the implementation of expeditious procedures offers geotechnical engineers the possibility of contributing beyond the typical site scale. For this purpose, several “typified” hydro-geomechanical-loading (HGL) models, which represent (simplified) scenarios of masonry buildings undergoing settlements, were set up to account for different predisposing/triggering factors (i.e. soil heterogeneity, loading conditions, and groundwater variations) of settlement occurrence in built-up areas. These models exploit multi-source wide-area input datasets encompassing the hydro-mechanical properties of geomaterials, in situ investigations and measurements (e.g. groundwater levels in wells), and innovative remote sensing data (i.e. DInSAR techniques). With reference to a district in Rotterdam City (the Netherlands), which was built on “soft soils”, the numerical simulations of different scenarios i) provide an overview of the comparative role of predisposing/triggering factors on settlement occurrence and ii) allow assessments of the expected induced damage to masonry buildings over thirty years with the exploitation of fragility curves. Considering the widespread diffusion of such geohazards, the proposed approach could help prioritise (rather expensive) maintenance work to the built heritage within sustainable strategies for subsidence risk mitigation.

Ground Surface Subsidence Monitoring Using Sentinel-1 in the “Kostolac” Open Pit Coal Mine

“…This was favorable for the InSAR methodology, which was used to capture four-year-long processes around the open pit contour. The groundwater regime is also highly influential [75], and it can be anticipated that the open pit wells are constantly lowering the table below the pit bottom so that the near-surface conditions are dry [74].…”

“…These are separated with an impermeable foil and then compacted to a dry density of 11 kN/m 3 . It is assumed that each tailing can reach up to 30 m with 1:1 slope sides, and is of sandy-silty composition [75]. The pit size and geometry During the observed period from April 2019 until February 2021, nine epochs were undertaken approximately every two months except for the last epoch, which was conducted at the beginning of 2021.…”

“…These are separated with an impermeable foil and then compacted to a dry density of 11 kN/m 3 . It is assumed that each tailing can reach up to 30 m with 1:1 slope sides, and is of sandy-silty composition [75]. The pit size and geometry were reconstructed using the available satellite imagery, and the depth was based on the coal layer's position.…”

“…Having in mind that the settlement model was simplified and based on roughly estimated input parameters, the comparison shows that the model fits reasonably well with the measured data, implying that the PS measurements have a valid trend and magnitude, despite apparent over/underestimations. Further improvements of the settlement model, which are currently not feasible due to a lack of operative geotechnical data, might result in an even better fit (e.g., assuming the presence of pore pressures [75] and primary consolidation or even secondary settlement, which might justify the analysis of a longer time series).…”

“…better fit (e.g., assuming the presence of pore pressures [75] and primary consolidation or even secondary settlement, which might justify the analysis of a longer time series).…”