基于DIC技术的桩–土–承台共同作用性状的 模型试验研究

 利用数字图像相关技术，编制适合岩土试验模型变形量测分析的位移场分析程序(DIC)。结合室内模型试验，利用DIC程序对试验中获得的系列图像进行分析，得到群桩基础的承载变形特性、桩周土体的位移场，并对其破坏模式进行推断。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；随着桩距增大，群桩基础荷载沉降特性有更多的天然地基承载表现；3b(b为方桩边长)桩距群桩由于桩对桩间土体的遮拦作用明显，其侧向位移数值较6b桩距的要小；对于3b桩距群桩，土体的压缩主要集中在桩端以下土层，整个群桩基础呈实体深基础破坏模式，而对于6b桩距群桩，桩间土体的压缩量占主导地位，整个基础因桩间土体侧向挤出而破坏。分析结果验证复合桩基理论，6b桩距可视为常规桩基与复合桩基的桩距分界点。

MODEL TESTS OF CHARACTERISTICS PILE-SOIL-CAP INTERACTION BASED ON DIGITAL IMAGE CORRELATION METHOD

Based on digital image correlation method，a deformation measurement procedure(DIC) has been worked out to study the pile-soil-cap nonlinear interaction mechanism. A series of images are captured by digital camera in the model test，and the images are analyzed by the DIC procedure. Bearing capacity and displacement field of soil beneath cap are obtained during the analysis. The failure pattern of pile foundation is deduced. The test results show that it is viable to analyze the displacement around pile by DIC procedure，and a full displacement field is obtained from image analysis. The deformation behavior of the group piles with 6b spacing is similar to that of single raft foundation. The soil lateral deformation of group piles with 6b spacing is larger than that of 3b spacing，and the pile barrier effect on soil lateral deformation decreases with the increase of pile spacing. The compression region is mainly centralized beneath the pile tip to the 3b spacing foundation，which presents a destruction pattern of block deep foundation. As the increase of pile spacing，the compression region transfers from pile tip to the soil among piles. Group piles with 6b spacing are destroyed by the lateral extrusion of the soil around piles. It is shown that validate the theory of composite pile foundation is validated and 6b spacing is the dividing value between the normally pile foundation and the composite pile foundation.