摘要:为了从细观角度分析桩土共同作用的内在机理,利用数字图像相关技术,通过室内模型试验得到了群桩基础的承载力特性、承台下土体可视化位移场,并结合有限元技术实现3维位移场分析。研究结果表明:群桩基础的荷载-沉降关系呈缓降型,常规桩基后期承载力由桩来控制;而复合桩基后期承载力由承台下土体控制,且荷载沉降特性更具天然地基承载特性。常规桩基位移影响范围在长度和宽度方向较之复合桩基要小。常规桩基桩间土体的压缩区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,而复合桩基桩间土体的压缩量占据主导地位,桩端以下土层的压缩量较小,承台下土体存在明显的锲形压缩区,呈天然地基的位移模式。随着桩距的增大,桩间土体侧向位移影响区域逐步由桩外侧土体向桩间土体过渡,且在承台下某一深度达到最大值,复合桩基因桩间土体侧向挤出而破坏。%In order to investigate the interaction behavior of pile-raft-soil from the microscopic view,the pile model test was carried out by adopting digital image correlation method,and the load-settlement curves,visualized displacement field beneath cap were obtained.The three dimension displacement field was got from the numerical analysis of ABAQUS.The study results showed that the load-settlement curves descended slowly,and the following load of ordinary pile foundation was taken by the piles.As for composite pile foundation,the following load was taken by the soil beneath cap,and presented more behavior of raft foundation.The displacement influence region of ordinary pile foundation such as in length and width was smaller than composite pile foundation.The compression region was mainly centralized beneath the pile tip to ordinary pile foundation,which presented a destruction pattern of block deep foundation.As to composite pile foundation,the compress region of soil around pile gradually became the dominant position,and the compress region of soil under pile tip became more and more small,a triangular compression zone existed immediately beneath the cap,which presents a displacement pattern of single cap.With the increase of pile space,the influence region of lateral soil deformation transfered from pile tips to the soil among piles,and got a maximum at a certain depth under cap.Composite pile foundation was destroyed by the lateral squeeze of the soil around piles.