Experimental Investigation and Analysis of the Influence of Depth and Moisture Content on the Relationship Between Subgrade California Bearing Ratio Tests and Cone Penetration Tests for Pavement Design

Evaluation of soil properties in highway design is an important but time-consuming task that does not always provide the necessary information to detect issues associated with changes in soil properties along the road project. California Bearing Ratio (CBR) tests are commonly used to identify soil properties and as an input in pavement design; however, it could be considered a slow test and, therefore, not always performed to the extent that it may be desired on the field. A comparison between CPT and CBR is performed in this work to obtain a correlation between them to be used in design. The effects of moisture content are also investigated in CPT and CBR to determine which conditions should be tested to obtain representative or design conditions for the pavement. A good correlation is found between CPT tip resistance and in situ CBR. It is observed that CBR and cone tip resistance change significantly for moisture contents up to 30 to 40%. It was found that tip resistance should be evaluated at a depth of 20 cm inside the subgrade to estimate adequate CBR values.

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