Development and evaluation of correlation of shear strength parameters for silty sand (SM) soils using SPT (N1)60 values in Gujarat, India

This study presents region-specific correlations between SPT (N 1 ) 60 values and shear strength parameters for Silty Sand (SM) soils based on data from 28 boreholes across Gujarat, India. Existing empirical models significantly overestimate the angle of internal friction (φ) for SM soils, potentially compromising geotechnical design. Two new correlations were developed for different (N 1 ) 60 ranges (1–60 and 60–100), incorporating field density and fines content. Validation against laboratory test results shows that these new models reduce prediction errors significantly. Bearing capacity and pile capacity were evaluated using both conventional and newly developed regional correlations, highlighting the variations and implications on design. The findings facilitate safer and more accurate geotechnical designs for infrastructure development in Gujarat.