Accurate prediction of both the magnitude and the time rate of consolidation settlement remains challenging in layered soft soils because key inputs—stress history (OCR), primary consolidation-rate parameter (cv), and the effective drainage distance (d)—are often uncertain and are commonly evaluated using laboratory tests, in-situ indices, or settlement records in isolation. This study presents a case-history comparison of these approaches using comprehensive site investigations and settlement monitoring from the Northern Marmara Highway (NMH/KMO) embankment. Preconsolidation pressure/OCR profiles were derived from laboratory consolidation curves and evaluated against independent field evidence using CPT- and SPT-based correlations; these OCR trends were then used in one-dimensional settlement calculations, including an additional stratified scenario in which drainage-competent sandy/silty strata were excluded from the compressible clay thickness based on CPT soil classification. For time-rate assessment, laboratory-based and CPT-dissipation-based cv were evaluated together with a liquid-limit-based range drawn from NAVFAC guidance, and the monitored settlement–time records were analysed using multiple observational fitting methods. The results show that settlement predictions are highly sensitive to OCR interpretation and drainage-distance assumptions in stratified deposits. When CPT-based drainage boundaries are incorporated into the interpretation of dissipation-derived in-situ indices, the resulting settlement–time predictions align with the monitored response. The study provides a practical basis for reconciling laboratory, in-situ, and monitoring-based inputs when assessing primary consolidation settlement in layered soils.
Doğan et al. (Thu,) studied this question.