Abstract
An extensive database of high-quality piezocone (CPTU) and laboratory oedometer test data on onshore and offshore clays worldwide has been established. The database covers a wide range of index parameters and overconsolidation ratios (OCR) in the range 1 to 5. The purpose is to derive general correlations to model preconsolidation stress in clays from CPTU data based on high-quality laboratory data. Several studies have already discussed such correlations for different clay types, where the preconsolidation stress is defined as a function of the cone resistance and/or the pore pressure measured in CPTU tests. Often, these correlations are characterized by high uncertainty, mainly because of the sample quality of the laboratory data. New correlations are proposed based on the new database. These correlations are meant to be used for preliminary assessment of preconsolidation stress in the absence of laboratory data or as a comparison tool when limited test data is available.
Highlights
The preconsolidation stress, or yield stress, σ'p is a fundamental and one of the most relevant engineering parameters of clays
Several studies have already discussed such correlations for different clay types, where the preconsolidation stress is defined as a function of the cone resistance and/or the pore pressure measured in CPTU tests
This paper presents a multivariate database consisting of 249 high-quality onshore and offshore clay data points, labeled as CLAY/9/249 database
Summary
The preconsolidation stress, or yield stress, σ'p is a fundamental and one of the most relevant engineering parameters of clays. Sample quality was assessed by means of the well-known criterion proposed by Lunne et al [5] This criterion considers the volume change during recompression to the in-situ stress (∆e/e0, where e is the void ratio) and the OCR. Based on a large data set consisting of 205 clay sites all over the world, Chen and Mayne [13] suggested k1 = 0.31 with a coefficient of determination r2 = 0.82 They further observed how correlations to σ'p resulted in higher r2 compared to correlations to OCR. The compiled CLAY/9/249 database is used to derive improved CPTU-based correlations for σ'p and OCR by means of linear regression analyses.
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