Volume 39, Issue 2 (March 2011)
Application of Dynamic Compaction for Poorly Compacted Embankment
This paper presents a successful application of dynamic compaction (DC) as a remedy to strengthen a poorly compacted expressway in Hunan (China). Comprehensive laboratory and in situ field tests were employed to determine the optimum drop height, number of tamping, grid spacing, and depth of densification that will achieve the most desirable results without damaging the underlying structure (culvert). Based on the density measurements and field observation, it was found that under Case I-2 conditions, the density increased from under 84 % to over 95 %. When the drop height was at 12 m, it caused heaving, an indication of displacing the soil plastically with no volume change. Thus, the optimal compaction parameters based on Case I-2 conditions were found to be 3.5 m spacing, 10 m drop height, 10 ton mass, and six tampings. The effectiveness of the DC under Case I-2 conditions was clearly demonstrated from the standard penetration test results, with a decrease of about ten blow counts for the top 4 m soil. In addition, there was a relative densification improvement of 50 % for the top 4.5 m soil. Case I-2 conditions were recommended to the highway authority, and it had been implemented to the entire expressway. A surface overlay was subsequently applied to the re-compacted embankment. To date (Spring 2010), no noticeable distresses have been observed after ∼12 months of opening to traffic. No structural damage to the underlying culvert was found either.