Performance of cement fly ash gravel column under consolidation condition

Abstract

This research was studied to increased strength in soft clay which is the main problem of Bangkok soft clay. By using gravel cement fly ash gravel column (CFG column) improve soil quality to support embankment or small structures. CFG column

was made by 4.75-19.50 mm. gravel which mixed with fly ash and cement. After that, the test was performed using a physical model in a PVC pipe with a diameter of 300 millimeters and a height of 450 millimeters. The size of CFG column used in the test are 200 mm. high. and diameter sizes are 50, 75 and 100 mm. which placed the column in a soft clay layer. The test results showed when the diameter of the column increased that the consolidation decreased and the drainage time decreased. In terms of soil stress was decreased when stress in column increased after increasing loading due to improvement areas (Ar) was increased. The result of excess pore water pressure at the same height, it was found that the radius near the column is lower than that the same time due to the porosity of CFG column. At the different depths was found that the excess pore water pressure increased as the depth increased because the stress at the top of soil was higher than lower depth that cause increasing excess pore water pressure. From the research can conclude that the CFG column can increased the bearing capacity of the soft clay and decreased consolidation by varying of column diameter size. Also, the CFG column are porous which allow good drainage. Resulting in excess pore water pressure near the column is lower which is different when the radius of soil increased.