Quasi-static Loading Effects on a Mar shalling Yard Calibration of a Creep-SCLAY1S Model Using Satellite and In Situ Measurements

Abstract

Marshalling yards on soft clay deposits are subject to long-term settlements driven by consolidation and creep, posing challenges for track geometry maintenance and operational reliability. This thesis investigates time-dependent settlement behaviour at Sävenäs marshalling yard in Gothenburg, Sweden, through numerical modelling using the Creep-SCLAY1S constitutive model in PLAXIS 2D. The model accounts for anisotropy, bonding and rate-dependent deformation, making it well suited for the soft Gothenburg clay conditions at the site. Model parameters were calibrated using site-specific oedometer and triaxial test data, supplemented by theoretical relationships and literature values for similar Scandinavian clay deposits. The cal ibrated model was validated against two independent field datasets: bellow hose measurements tracking subsurface deformation at multiple depths, and surface set tlement rates derived from Sentinel-1 InSAR observations. Good agreement was achieved at most monitoring locations, with simulated long-term settlement rates of approximately 4–5 mm/year consistent with satellite observations. The variabil ity observed in InSAR data within the depot area is interpreted as reflecting cyclic vertical movements from operational loading rather than measurement noise. Oper ational loading was represented using a quasi-static approach, where train loads were activated and deactivated over time according to track occupancy patterns. The re sults show that excess pore pressure and settlements are most pronounced in the upper soil layers, with the influence of loading diminishing clearly with depth. Par tial pore pressure dissipation between load cycles prevented progressive settlement acceleration, and the response approached a stable long-term condition consistent with partially drained behaviour. For preliminary assessments, a simplified con stant load of approximately 50% of the full load was found to produce comparable results to the quasi-static scheme if only settlements in the clay is of interest. The study demonstrates that advanced constitutive modelling combined with remote sensing validation provides a reliable framework for assessing long-term settlement behaviour in railway infrastructure on soft clay.