Improved use of seismic profiles to estimate allowable pressure in granular soils: Application to quaternary deposits with different gradings

Abstract Herein, a new approach for widening the applicability of seismic refraction profiles in shallow foundation designs is presented. To provide quantitative geotechnical information, a relationship was established to estimate the allowable bearing pressure of cohesionless soils according to the results of seismic refraction measurements, without the conventional uncertainty. The developed procedure was employed in the geomechanical characterization survey for the construction of a helipad at the centre of the Iberian Peninsula; here, seismic refraction tomography was used to compute sections of the velocity–depth curves using the wavepath eikonal traveltime inversion method. When the shear- and compressional-wave one-off velocities are transformed into dynamic moduli through conventional elastic equations, dynamic moduli images that provide quasi-continuous information on soil deformation properties can be generated. These results were combined with the data from dynamic probing super-heavy tests to evaluate the stress–strain moduli relationships, and the dynamic moduli were used to determine the bearing capacity. Furthermore, a general equation for the allowable bearing pressure in granular soils is proposed; this equation contains a new variable that depends on the grain size grading of the zone. Using this, the distribution of the allowable bearing pressure can be used as a criterion to detect spatial variability and problematic zones. The proposed methodology provides more deformation properties of subsoil; thus, it reduces the costs of ground-testing techniques as the boreholes can be better located according to the project foundation requirements.