Field Test Study on the Improvement Mechanism of Pile-Net Composite Foundation

In this paper,experimental sections in Guangdong highway soft soil treatment project are designed to investigate the working mechanism of pile-net composite foundation under embankment loads,and analyze its settlement,load transfer,pile-soil stress ratio and internal force of net etc.The results show that pile-net composite foundation could be used in the roads with high-fill and large-depth soft soil to eliminate the settlement effectively.The deformation of the tubular pile is out of harmony with that of soil and the effect of the geogrid to adjust the efficacy of pile and soil is obvious.In long pile area,there is considerable difference in the pile-soil stress ratio between the locations above and below the geogrid,and the maximum stress ratio approaches 80.The pile-soil stress ratio of the short pile whose end does not reach the bearing stratum is within the range of 14～22.As the settlement difference increases,the pull effect of geogrid is exerted.The load transfer efficacy of the geogrid is better than that of the soil arch,and they all reach 30% under the full load.The maximum strain of geogrid,which occurs at the edge of pile cap,is just 1%,and the minimum strain occurs at the midst of two piles.