基于DIC技术的桩筏基础工作机理研究

为了深入研究桩筏基础中桩周土体位移场特性及其工作机理，以数字图像相关技术（DIC）的基本原理为基础，编制相应的位移场分析程序，并利用该程序对桩基模型试验中获得的系列图像进行分析，得到了桩周土体位移场渐进性发展变化的全过程，同时对不同桩距桩筏基础的破坏模式作出推断。研究结果表明：利用自行编制的DIC程序分析桩周土体位移场是可行的，并可以得到全场位移。对于不同桩距桩筏基础，小桩距削弱基桩承载力，随着桩距的增大，这种削弱作用减弱。3b（b为方桩边长）桩距桩筏基础中，土体压缩区主要集中在桩端以下土层，基本符合实体深基础的破坏模式；而6b桩距桩筏基础，土体变形区域主要集中在桩身上部1/3L（L为桩长）范围内，明显小于3b桩距桩筏基础的影响深度，基础最终因桩间土体侧向挤出而破坏。

Research on working mechanism of pile raft foundation based on digital image correlation method

In order to study displacement field characteristics and working mechanism of pile raft foundation, a displacement analysis procedure is worked out based on digital image correlation (DIC) method. This procedure is used to study a series of images captured from the model test on pile raft foundation; the whole gradual deformation process of soil around piles is got from this analysis; the failure pattern of pile foundation is also deduced. The study results show that it is viable to analyze the displacement field around piles by the procedure of DIC; and a full displacement field is got from this analysis. Small pile spacing will weaken the single pile bearing capacity. The compressive region is mainly centralized in the soil beneath the pile tip to the pile raft foundation with 3b spacing, which presents a massive deep foundation failure pattern. But to the pile raft foundation with 6b spacing, the compressive region is mainly on the upper part of pile which is about 1/3 of pile length; the displacement influence length evidently smaller than the pile raft foundation with 3b spacing; and it is destroyed by the lateral squeeze of the soil around piles.