Study On Working Characteristics Of Variable Cross-Section Pipe-Pile Composite Foundation Under Rigid Foundation

This paper relies on the National Natural Science Foundation of China "Study on single pile bearing capability and connection key technology of steps section concrete precast pipe pile(Project Number:51208194) ", by large indoor model test and numerical simulation, the composite foundation working characteristics between open-end ladder-type variable cross-section pipe-pile and open-end constant section pipe-pile are comparatively studied. The pile group composite foundation bearing behavior between ladder-type variable cross-section pipe-pile and constant section pipe-pile are comparatively studied by numerical simulation. The chief contents are carried out as follows:1.Based on indoor large scale model experiments of open-end ladder-type variable cross-section pipe-pile and open-end constant section pipe-pile composite foundation, the test results on their working characteristics are comparatively studied. The change law of load-settlement, pile shaft force, pile-soil stress ratio and pile-soil load share ratio of open-end ladder-type variable cross-section pipe-pile composite foundation and open-end constant section pipe-pile composite foundation have been studied. The results show that the bearing capacity,pile-soil stress ratio and pile-soil load share ratio of open-end ladder-type variable cross-section pipe-pile composite foundation are greater than those of open-end constant section pipe-pile composite foundation. And,by adopting the technology of open-end ladder-type variable cross-section pipe-pile composite foundation, on the one hand, it can effectively improve the stress behaviors of pile and reduce the foundation settlement; on the other hand, it also can reduce the dosage of pile material and has good socioeconomic benefits.2.Based on FLAC3 D, the finite difference model of the composite foundation-soil interaction is established. The stress field and displacement field variation of open-end ladder-type variable cross-section pipe-pile, open-end constant section pipe-pile and their composite foundation have been studied. The load sharing ratio under rigid foundation of the center pile, the side-center pile and the corner pilehave been discussed. The relationship between composite foundation settlement and pile soil physical parameters was discussed. The correctness and rationality of the numerical simulation model’s results are verified by large scale indoor composite foundation model.