Abstract：In order to exactly determine the bearing capacity of composite foundation with cement-flyash-gravel (CFG)piles by in-situ static loading test and study the influence of cushion thickness and material on the bearing capacity，six vertical loading plate tests of composite foundation with single CFG pile were carried out in field with various cushion thicknesses. Six earth pressure gauges were embeded in the cushion for each loading test to measure the soil resistance. Based on the test results，the stress ratio，n，of pile to soil，bearing load ratio，k，of pile to soil，and the development of stress ratio with time are analyzed. It is shown that the thickness and material of cushion have great influence on the bearing capacity of composite foundation with CFG pile in loading test，and there is a match problem between them. The suitable cushion thickness is 50～150 mm for a mixture of coarse sand and detritus，and the developing coefficient of bearing capacity of the soil between piles is 0.75～1.0.
