Test Research On Behavior Of Tall Building's Rigid Pile Composite-foundation Under Raft Foundation

Rigid pile composite foundation has been in great use in tall building's construction with the development of ground-improving technique. The bearing capability and failure mechanism of the group pile composite foundation are not very clear and the difference between single pile composite-foundation and group pile composite foundation is still an uncertain problem at the present time.The work behaviors study of uneven distributed rigid pile composite foundation under raft foundation based on on-site test has been finished. The bearing and failure mechanism of rigid pile composite foundation under the raft foundation were disclosed and the interaction between pile and soil was also discussed.The relations between load levels and settlement and the stress ratio of pile and soil were analyzed. The difference of composite foundation bearing capacity characteristic values was noticed, one coming from group pile load test under raft foundation, and the other coming from single pile composite foundation theory formula. Then the composite foundation safety was analyzed.Group pile effect and minus friction should be considered in the design and test of composite foundation. A suggestion was made that the formula of composite foundation be modified.An attempt was made to analyze the rigid pile composite foundation with load transferring function and the result was very similar to that of the model test. Non-linear model of soil shear resistance was used in the analyses.Based on a representative project example, the method is proved reliable to calculate the sedimentation of composite foundation. The rationality of the model test's results is proved by engineering practice.