超大面积深厚软土桩-网复合地基承载性状模型试验研究

基于厦深铁路潮汕车站地基处理加固工程，完全参照原型的软土地基地层分布情况，设计了两种不同桩间距下的超大面积深厚软土桩-网复合地基物理模型试验，对荷载传递机制与不同桩间距下桩体荷载分担比、桩土应力比及地基沉降规律等进行了系统研究。结果表明，桩身轴力沿着桩身高度往下先逐渐增大到某一深度后又逐渐减小，随着桩间距增大，桩承担上部荷载的方式由摩擦桩逐渐向端承桩变化；随着桩间距增大，桩身中性点下移，桩身最大负摩阻力出现的位置下降，且其值减小；桩间距对桩-土应力比有显著影响，而对桩体荷载分担比影响较小；不同桩间距下，两桩中心桩间土与桩顶差异沉降均小于4桩中心桩间土与桩顶差异沉降；随着路堤填土荷载增加，土工格栅表现为拉应变逐渐增大，拉应变曲线刚开始比较平缓，后逐渐变陡，增大的速率先慢后快。

Model test research on bearing behavior of pile-net composite foundation on oversized deep soft soil

Based on the foundation treatments of Xiamen-Shenzhen railway Chaoshan station and in-situ distribution of soft soil layers, two laboratory models of pile-net composite foundation with different pile spacings are designed to study the load transfer mechanism, pile load sharing ratio, pile-soil stress ratio and settlement laws. The results show that the axial force of pile shaft increases first down along pile shaft to a certain depth, then gradually reduces. With the increment of pile spacing, the bearing pattern tends to be ending-bearing form; and the neutral point and the position of maximum negative skin friction move down. The pile spacing has obvious effect on pile-soil stress ratio, but minor influence on pile load sharing ratio. The differential settlement of center soil between piles and pile top is smaller for double pile than that of four piles. Tensile strain of geogrid rises gradually as the embankment filling load increasing; tensile strain curve is initially smooth, then steepening gradually; the rising rate of curve is slow at first then becomes fast afterwards.