CPT Based Settlement Prediction over California Soft Rock, Stiff Alluvium, and Soft Alluvial Sites

Settlement is a critical parameter for designing foundations. Geotechnical engineers routinely struggle with overestimation of settlement of shallow foundations bearing on soft rock and stiff soil sites due to sample disturbance, resulting in unnecessary conservatism and potential underestimation of ground subsidence for sensitive soils. This paper evaluates three case histories where settlements were measured at a soft rock, a stiff alluvium, and a soft clay site. Several methods were considered to estimate the settlements. These methods included: (1) using finite element analysis based on the Winkler foundation model and subgrade modulus based on elastic properties of the subgrade, (2) Terzaghi’s traditional one-dimensional consolidation theory using laboratory tests, and (3) Terzaghi’s one-dimensional consolidation theory based on constrained modulus using CPT results. These analyses were compared with actual survey results taken during the construction to determine the most suitable method for estimating settlement in various conditions.