Unconservative Outcomes from Conservative Soil Properties Used in Waterfront Applications

In light of the inherent variability and soft nature of soil deposits in the marine environment, it is common geotechnical engineering practice to use conservative soil property values for analysis and design recommendations. The shear strength and modulus values often recommended are generally smaller than best estimate or mean values. The connotation that lower bound values are conservative can be related to the use of limit-equilibrium analyses for stability applications involving foundations, earth retention systems, and slopes. Current use of numerical models for performance-based design at ports has demonstrated, however, that the assumption that lower bound soil properties yield conservative results is not always accurate. This paper presents two examples in which lower values of strength and/or modulus resulted in unconservative estimates of performance for the design of port waterfront structures.