Use of SPT Blow Counts to Estimate Shear Strength Properties of Soils: Energy Balance Approach

Abstract

In foundation designs, standard penetration test (SPT) blow counts are typically used to estimate shear strength properties of soils. Few correlations are widely in use to make such estimations. However, the selection of these correlation equations are not often justified or explained. This manuscript describes a new approach to estimate the shear strength properties based on the SPT blow counts. The proposed method treats SPT analogous to driving a miniature open-ended pipe pile. During SPT, part of the energy is transferred into the soil. This energy is dissipated at the soil-sampler interface to overcome skin and point resistance to penetrate a sampler into the soil. Energy balance was used to correlate the SPT blow count to the shear strength properties of the soil at the depth of testing. Two separate equations were derived: one to estimate the friction angle