桩-网复合地基加固机理现场试验研究

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

通过在广东某环城高速公路深厚软土地基加固工程中设置桩—网复合地基试验段,研究路堤荷载下桩—网复合地基的工作机理,深入分析其沉降变形、荷载传递、桩土应力比、网的受力等性状。试验成果表明：桩—网复合地基可以有效减少沉降量,可以用于填土高、软土厚度大的路段;路堤荷载下管桩与桩间土沉降不协调,土工格栅调节桩土分荷比的作用非常明显;长桩区格栅上、下的桩土应力比相差较大,桩土应力比最大值接近80;未达到持力层上的短桩桩土应力在14-22之间比较小,格栅兜提作用随桩土沉降差增大而得到发挥;在传递荷载方面,格栅作用要强于土拱的作用,满载时各向桩顶传递30%左右的荷载,土工格栅应变最大仅为1%,且桩帽边缘处应变最大,桩间应变最小。

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 con- siderable 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 iust 1%, and the minimum strain occurs at the midst of two piles.