Determination of Sand Void Ratio Using CPT and SPT

Undisturbed sampling of sands is practically difficult or even, at times, completely unfeasible. Hence, the determinations of in situ void ratios and/or relative densities of uncemented sands are generally achieved using correlations with the cone penetration test (CPT) and the standard penetration test (SPT). Different sands of the same relative density may have dissimilar CPT and SPT resistances because of their compressibility differences. Accordingly, the effect of compressibility should be considered while assessing the results of these tests. In this paper, an attempt is made to quantitatively incorporate the sand compressibility into the void ratio and/or relative density correlations. The presented approach utilizes compressibility indicators to quantify the effect of sand compressibility. The proposed relationships are formulated based on a published worldwide sand database that was inferred from the testing of high-quality undisturbed samples. It is demonstrated that these relationships can be utilized to reliably assess the void ratios of sands using the CPT and SPT. Two case studies are analyzed, and the estimated void ratios are found to be in a close agreement with the values inferred from undisturbed samples and other tests.