Revisiting interpretation of relative density from shallow depth CPTs in sand
L. Krogh, Santiago Quinteros, Harun Kürşat Engin, Tom Lunne
Abstract
The relative density is an important state parameter in the determination of engineering properties of marine sands. Existing industry-acknowledged cone penetration test (CPT) correlations to relative density have been developed almost exclusively from the results of calibration chamber testing performed at stress levels higher than 50 kPa. A few studies suggest correlations for low stress levels as well, however, mainly for unaged normally consolidated soils. Existing formulations are often found to be challenged in the application for dense to very dense aged overconsolidated marine sands. This paper investigates the conditions and response of overconsolidated medium dense to very dense sand (as typically found in the North Sea) at shallow depths (less than 50 kPa) for a penetrating cone. It provides recommendations for a consistent set of parameters linking CPT parameters to the stress conditions, expressed by the apparent overconsolidation ratio and coefficient of earth pressure at rest, and the relative density. The recommendations are based on a comprehensive field-testing campaign at a sand site in Cuxhaven, Germany, supported by a suite of laboratory testing and numerical analyses.