（1同济大学，上海200092；2上海林同炎李国豪土建工程咨询有限公司 200093）

［提要］对于特大桩距的复合桩基，当单桩为摩擦桩(或端承力较小的端承摩擦桩)时可认为各桩的工作状态将从弹性支承转为完全塑性支承，即塑性支承桩。在满足整体安全度的前提下，可令各单桩工作荷载接近或等于其极限荷载，其余荷载由地基土承担，最终的沉降状态由地基土的抗变形能力控制。介绍了基于此概念的复合桩基设计方法，对整体安全度及沉降验算等问题进行探讨，提出了改进方法和设计建议，计算结果与工程实测数据比较吻合，在设计实践中取得了很好的经济效益。

［关键词］塑性支承桩；复合桩基；安全度；沉降计算

Design and Discussion of Composite Pile Foundation Based on Concept of Plastically Bearing Pile/Liu Luyang1，Li Yingbao2（1 Tongji University，Shanghai 200092，China；2 Lin Tongyan & Li Guohao Consultants Shanghai Ltd.，Shanghai 200093，China)

Abstract:For the composite pile which has extremely large pile spacing, when single pile is a friction pile (or an end bearing friction pile having very small end bearing capacity), it can be considered that each pile"s working condition changes from elastic support to completely plastically support, namely plastically bearing pile. Under the degree of integrality safety, it can be assumed that each pile"s working stress can nearly reach or equal to ultimate load, and the rest load will be shared by soil. The final settlement is controlled by the anti-deformation characteristic of soil. The design method of composite pile based on this concept is introduced, and the degree of integrality safety and the settlement calculation are discussed. The improved method and design recommendation for the project are given, and the results meet the field experiment in engineering practice very well.The application to designing practice shows a good economical efficiency.

Keywords:plastically bearing pile; composite pile foundation; degree of safety; settlement calculation