Field tests on composite foundation with concrete-cored sand-gravel piles

Based on the idea of controlling post-construction and differential settlements,a new type of composite foundation,composite foundation with named concrete-cored sand-gravel piles for thick and soft ground,was introduced.The new composite foundation was composed of the concrete-cored sand-gravel piles,the soil between piles and the cushion.The outstanding advantage of the new technology was that the sand-gravel shell was employed as the vertical employed drainage to speed up the consolidation of soil between piles during the construction and preloading periods to reduce the post-construction settlement.A series of field test results including the pile-soil stress ratio,the settlement and differential settlement of piles and soil,the settlement in each loyer,the lateral displacement,the excess pore water pressure and the stress in piles were introduced.It is concluded that the technology of the new style composite foundation had many advantages,that is,small and differential post-construction settlements,reliable quality and high bearing capacity,especially for soft soil with high content of water and organic matter.