Impact of geological conceptualization in predicting pore pressure reduction from urban excavations

Leakage of groundwater and subsequent pore pressure reduction can cause consolidation in subsidence sensitive soils and subsequently pose damage risks to the built environment. This study presents the first systematic, quantitative evaluation of how geological conceptualization – specifically the inclusion or exclusion of permeable sand lenses within glaciomarine clay deposits - affects simulated pore pressure reduction due to groundwater leakage into deep excavations. By employing Multiple Point Statistics (MPS) to generate alternative geological models and integrating these with MODFLOW-NWT transient groundwater simulations, we reveal that the presence and hydraulic connectivity of sand lenses significantly influence the rate and magnitude of pore pressure reduction in clay, which has significant consequences for settlement magnitudes. These findings underscore the importance of explicitly accounting for geological heterogeneity and uncertainty in risk assessment for urban excavations, a factor often neglected in conventional engineering geology practice when assessing settlement hazards and their consequences for the surrounding areas. • Geological conceptualization impacts pore-pressure reduction in urban excavations. • Representation of more permeable interbedded layers improves accuracy of groundwater drawdown predictions. • Multiple Point Statistics used for expert-like geological characterization and risk assessment.