EFFECT OF RIGID PILES ON BEARING PROPERTIES OF COMPOSITE FOUNDATION WITH GEOGRID-REINFORCED CUSHIONS SUPPORTED WITH PILES SUBJECTED TO CYCLIC LOADS

Rigid pile has obvious effects on bearing properties of composite foundation with reinforced cushions. However, the effect of rigid piles on properties of composite foundation was still in research and the achievements were rarely reported. The changing laws of foundation subsidence, stress of piles and tensile forces of geogrids were analyzed based on some groups of model tests of composite foundation with geogrid-reinforced cushions supported with flexible piles or flexible-rigid piles. The test results showed that subsidence of composite foundation increased with the cycles of cyclic loads. The subsidence of composite foundation could be reduced by addition of rigid piles or of geogrid layers. The effect of adding rigid piles was more obvious than that of adding geogrid layers on reducing subsidence. Axial forces of piles first increased then decreasd along the pile shafts, and the axial forces increased with cycles of cyclic loads. The addition of rigid piles could reduce loads shared by side and corner piles in the same condition of cyclic loads. The tensile forces of geogrids increased with cycles of cyclic loads. The closer to the pile, the greater the tensile forces in geogrids. Tensile forces in geogrids reached the maximum at the junctions of piles and soil. The addition of rigid piles could not only change the distribution of tension forces in geogrids but also increase the tension forces in geogrids.