Predicting Shear Strength Properties for Low-Sensitivity Granular-Cohesive Soils from SPT Results

摘要

Several correlations between the standard penetration test (SPT) N-values andinternal friction angle (Φ’) have been developed for granular soils. Some correlationshave also been developed for un-drained shear strength of saturated clays. However,in many instances soils do not behave as either saturated clay or sand. Sometimes itis important to find the contribution of Φ’ in clays with higher silt and sand content;and cohesion in sands that has sufficient clay and silt content. It is incorrect toclassify these soils as cohesive soils with no friction angle, or as granular soils withno cohesion, and is thus the focus of this research. This paper describes a researcheffort to develop practical relationships between Φ’, effective cohesion (c’) and SPTN-values for granular-cohesive soils. Considering the SPT analogous to a miniaturepipe pile, an energy-balance approach was taken to derive a relationship between Φ’,c’, N-values and effective overburden pressure (σ’). A second relationship wasderived between Φ’, c’, σ’ and the liquidity index (LI) of low-sensitivity granularcohesivesoils. The two relationships were then graphically solved to formulate directcorrelations between field N-values and c’ and Φ’.