On the prediction of settlement from high-resolution shear-wave reflection seismic data: The Trondheim harbour case study, mid Norway

This paper presents a novel approach to predict long-term settlement in the Trondheim harbour, mid Norway, from high-resolution shear-wave seismic reflection data, complemented with cone penetration test results (CPTU) and index soil properties from nearby boreholes in this reclaimed coastal area. The data enables sub-surface geo-characterisation in high-resolution, down to the basement at a depth of about 175m. Correlations between shear-wave velocity and Janbu's classical 1D consolidation parameters (m, M0, M1, σ′c and OCR) are used for settlement analysis. Both the magnitude and rate of time-settlement predictions compare well with the measured settlements from GPS levelling and PSInSAR data acquired since the late 1980s and the early 1990s in the area, respectively. The shear-wave reflection data further provide important input to understand the spatial patterns of land-subsidence in the Trondheim harbour. The highest settlement rates occur in areas where depth to bedrock is greatest and where thicker deposits with low stiffness are found. In summary, the data and workflow presented here are useful tools for predicting settlements based on correlations with shear-wave velocity measurements.