Quality assurance and quality control of subgrade compaction using the dynamic cone penetrometer

Abstract

The Dynamic Cone Penetrometer (DCP) is a device that is used in the construction industry for the assessment of in situ soil compaction quality. Over the past few decades, numerous correlations have been developed between the DCP test results and soil strength and stiffness parameters. This paper proposes a comprehensive set of criteria and recommendations for quality control (QC) of compacted subgrade that take into account the inherent statistical variability of DCP test results. For the development of the QC criteria, a new statistical methodology is used to extract representative test values from the raw field DCP test data. In order to use the proposed QC criteria, soils are first classified into two broad categories (fine-grained and coarse-grained) depending on their fabric and response to compaction efforts. Test results indicate that (i) for fine-grained soils, the DCP test values have good correlation with the plasticity index (PI), which is indicative of the type and amount of clay content of the soil and (ii) for coarse-grained soils, the DCP test values have good correlation with the optimum water content of the soil, which is directly related to its in situ density. DCP blow count correlation equations are presented for both soil categories. Recommendations for field DCP testing and data analysis are also provided to highlight the significance of the statistical distribution of the DCP test results in QC testing of compacted subgrade.

Keywords:

• Dynamic cone penetrometer
• quality assurance
• quality control
• subgrade
• compacted soil

Acknowledgement

The authors would like to acknowledge the financial and technical support provided by the Indiana Department of Transportation (INDOT) via the Joint Transport Research Program (JTRP) for this study. The testing programme from which the data was obtained was a part of the JTRP-SPR 3635 research study titled QA/QC of subgrade and embankment construction-technology replacement and updated procedures.

Additional information

Funding

This work was supported by Indiana Department of Transportation (INDOT) [grant numbers SPR-3635 and SPR-3009].