Engineering characteristics of crushed stone and coal ash mixture compaction piles

Crushed stone compaction piles are widely used for soft ground improvement because the installed piles improve both overall composite capacity and discharge capacity. However, discharge capacity declines when clogging occurs due to clay penetrating into the voids of crushed stone compaction piles over time. In this study, research was performed to reduce clogging and minimize voids in a crushed stone compaction pile constructed in soft ground. An optimal mixing ratio was determined based on large scale direct shear tests that were conducted to identify strength and permeability levels that would provide the best mixing ratio of crushed stone and bottom ash. The test results indicated that the highest internal friction angles were obtained at an 80:20 mixing ratio of crushed stone and bottom ash. The internal friction angle declined when the mixing ratio of the bottom ash became greater than 20%. The results of clogging tests indicated that a mixture of 80:20 crushed stone and bottom ash is more effective than pure crushed stone for reducing clogging.