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Soil strength from geophysical measurements for soft clays

Abstract

Knowledge of seabed soils is essential if offshore and nearshore structures are to be safely designed and properly built. A large part of the commercial and operational risk involved relates to uncertainties about the soil properties at the site. It is therefore important to perform sufficient investigation to evaluate these risks thoroughly. Geophysical surveys are required to understand the nature and characteristics of the seabed. Site specific correlations between soil strength and various geophysical measurements can be developed, but a controlled laboratory study is required to highlight variability in these correlations for a range of geotechnical material. This work presents the development of a framework for correlating sediment strength, undrained shear strength, for soft clays to geophysical measurements, primarily shear wave and body wave velocities. Small strain measurements using elastic waves provide valuable soil information without altering the soil fabric. The small strain shear modulus (Gmax) is an indicator of many soil properties such as density, soil stiffness, sample disturbance, and can be calculated using the shear wave velocity (Vs) values measured by bender elements. Influence of variables such as soil density, confining stress, and stress history on shear modulus are also examined.The authors would like to acknowledge the Naval Facilities Engineering Service Center (NAVFAC ESC) and the project Material Uncertainties in Assessing Soil Strength from Geophysical Surveys, BAA number: N6258312R0708.This is the accepted manuscript. The final version is available at http://www.isope.org/publications/proceedings/ISOPE/ISOPE%202015/index.htm

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