Assessing Small-Strain Shear Modulus Based On In Situ Seismic Measurements in Bay of Campeche Sand

Abstract A database with in situ measurements of shear wave velocity (VS), cone tip resistance (qc), and basic soil properties of sand has been established from fifteen offshore geotechnical investigations performed in the Bay of Campeche. VS values were obtained from P-S logging. The database was tailored to develop empirical correlations for small-strain shear modulus (Gmax) based on qc (or relative density), void ratio, and effective stress. Three empirical correlations were developed to determine Gmax based on: 1) void ratio, effective vertical stress, and coefficient of lateral earth pressure at rest; 2) effective vertical stress and relative density determined from CPT data; and 3) effective vertical stress and cone tip resistance. To evaluate the accuracy of the correlations, a comparison was made between VS computed from the three empirical correlations and in situ VS measurements at an independent site. The predictions of VS fall in a rather narrow band, 15 % lower and higher than the in situ VS measurement, which supports the conclusion that these equations provide a useful approach to estimating VS or Gmax for use in ground response analyses or offshore wind farm foundation design at sites where time constraints and finite resources prevent the feasibility of making in situ VS measurements.