No abstract

In this research, unconfined compressive strength and stiffness of modified subgrade soil by cement or fly ash were evaluated. Gyratory compactor, which could simulate the field compaction, was adopted to make the test specimen. The testing soil from Cheonan area was used and its classification was SP. The optimum moisture content and maximum dry unit weight of soil were determined, and cement or fly ash was added, 4%, 8% and 12%. Curing times, such as 7, 14 and 28 day were adopted. An unconfined compressive test, an impact resonant test and an LFWD(Lightweight Falling Weight Deflectometer) were carried out to evaluate the strength or stiffness of modified soil. The strength of modified soil increased as the amount of cement and its curing time were increased. However, the strength or stiffness of fly ash modified soil was not significant. The correlation of unconfined compressive test and impact resonant test was relatively good.