The aim of this research is to establish practical and robust correlations between dilatational wave velocities (p-wave velocities, Vp) and the Standard Penetration Test blow count (SPT-N). Very low levels of correlation are recorded with the conventional single variable approaches, in consequence, a multivariable study is needed for higher precision. A dimensional analysis was conducted including other soil parameters that condition this physical phenomenon, such as the void ratio (e), the degree of saturation (Sr), the effective overburden pressure (σ′v), and the particle density (γs), for greater precision with Vp and SPT-N correlations. Over 100 seismic and SPT tests were performed around the coastal city of Juchitán de Zaragoza (Oaxaca), Mexico, to gather information for this research. As a result, two dimensionless indexes -DSIu (Undrained Dilatational Stiffness Index) and MDSIu (Modified Undrained Dilatational Stiffness Index)- yielded two alternative expressions between both indexes and Vp. In this way, a strong relationship between Vp and SPT-N was obtained with an adjusted coefficient of determination R2 value of 0.93.
