In the highway widening project, it is of great importance to take measures to control the differential settlement between the new and old embankment, therefore improving the stability of the new embankment. This article presents a series of model tests to analyze the failure law of the new embankment and compare the reinforcement effects of different reinforcement technologies. The test results show that the new embankment is unstable because of the slope slippage under ultimate load. In the reinforcement test of gravel pile, reaming phenomenon occurred at the top of the pile, and both of the values in pavement settlement and embankment lateral deformation are similar to those of the unreinforced embankment. In the geogrid reinforcement test, the embankment settlement can be reduced by restricting the lateral deformation of the new embankment with geogrid, where the settlement is 41 % less than that of the unreinforced scenario. In the cement fly ash gravel (CFG) reinforcement test, the pavement load is transferred to a deeper layer of the embankment by CFG piles, a soil arch effect with the surrounding soil is formed to restrict the lateral deformation and slippage, and the pavement settlement is 46 % less than that of the unreinforced scenario. According to the test results, the order of effectiveness for the reinforcement methods is CFG piles > geogrid > gravel pile.

The reinforcement treatment for embankment using the fly ash deposits as the filling material for roadbed was clarified in this paper. Studies have shown that fly ash can be used as the filling material for embankment, but the subgrade bearing capacity from the original fly ash deposits cannot meet the requirements for operating. Fly ash has a good condition to run the dynamic consolidation for meeting the requirements of embankment compaction. The modulus of resilience and the California bearing ratio (CBR) of fly ash is close to that of general filling material for embankment. Fly ash also has the engineering properties of high void ratio and low cohesion. The maximum level of compaction of the fly ash deposits can be 93% and the bear capacity can be about twice over before after the treatment.

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.