Correlation between CBR and Resistance to Unconfned Compression
Abstract
The thickness and layer properties of a pavement structure are highly determined by subgrade stiffness. However, in some cases, performing direct stiffness tests is impossible, at least for
the required frequency, which indicates that correlations with other soil properties must be used.
Therefore, this paper reveals the results from an experimental program conducted to obtain correlations between the California bearing ratio (CBR) of undisturbed fne-grained soils and their unconfned compressive strength and/or some index properties. For these purposes, CBR, unconfned
compressive strength, Atterberg limits, granulometry, and natural moisture content tests were performed. Thirty-eight samples were selected to guarantee a statistical power and confdence level of
95%, together with minimum Pearson correlation coefcient (r) of 0.60. Although correlating the CBR
with the index properties assessed was impossible, the study made correlations between the natural and saturated CBR and unconfned compressive strength. These correlations, at r > 0.80, were
then compared against the correlations reported in the literature between CBR and other undrained
shear strength tests. For the same strength, the CBR values determined herein are considerably
smaller than the correlations reported in the literature.
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References
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