Performance Evaluation of Abandoned Fly Ash Deposit Improved by Dynamic Compaction for Construction of Highway Embankment

In developing countries such as India and China, large amounts of unused fly ash were landfilled into ash deposit on uncultivated land. With an increase in traffic engineering, these ash ponds could probably be reclaimed to construct heavyweight engineering. This requires sufficient strength of foundation to ensure the safety of engineering located on the fly ash deposit. In this paper, a successful utilization of dynamic compaction on a fly ash pond is reported based on embankment engineering of a national highway. Field and lab tests of the ponded ash before and after the compaction are carried out, showing calibration of construction parameters and increased strength of the compacted ash. It has been found that the drop numbers should be determined mainly by the calculated total of penetrated settlement, though the increase in the penetrated settlement is less than 5 cm. The limited value of the bearing capacity of the post-compacted ash can be increased by about 300 %, which meets the design requirement of strength. Results also show that the improved thickness and bearing capacity at the side compaction locations are lower than those of the central position because of the boundary effect. Considering the slope stability of embankment under traffic loading, at least two main compaction locations should be set outside the boundary of the slope toe in the design process.