Study On The Laws Of Bearing Features Of Multi-element Pile Composite Foundation

Multi-element Pile Composite Foundation could play better baring capacity and promotepiles and soil working together which is benefitial for developing the potention of thecomposite foundation. This technology is widely used is practical engineering but the studyon is is still not enough to provide guidance. This thesis is rely on Natrual Science Foundationof China(No.51279171） and using numerical modeling to establish several models tosimulate different kinds of composite foundation to analysis its characteristic. And finally,these conclusions have been worked out.(1) Through establishing models of multi-element pile composite foundation underflexible foundation, the following rules are concluded. The combination of the long piles andshort piles, rigid piles and flexible piles could provide better performance of the compositefoundation on settlement, baring capacity, differential settlement ans so on. With the loads oftraffic, composite foundation usually could not reach the plasitic zone and its ultimate bearingcapacity. The increasing of the long piles has significant meaning on decreasing the settlementof the composite foundation while the length of short piles has less meaning on this point.(2) Through establishing models of multi-element pile composite foundation under rigidfoundation, the following rules are concluded. Before reaching the plasitic zone, theincreasing of the piles elasticity modulus has little effect on decreasing the settlement andgreat effect on imoroving the bearing capacity of the composite foundation. The thickness ofthe raft has no effect on the settlement of the piles but could make some development ondecreasing the defferential settlement of the piles and soil. But after the rafe becoming thickenough, this kind of impact would tend to reduce. The increasement of the ratial of short pilescould reduce the settlement while the increasement of the ratial of long piles could improvethe bearing capacity of the composite foundation.(3)For piles of both of the flexible foundation and rigid foundation, there is negativefriction for long piles and short piles. The critical point from positive friction to negativefriction grows with the growing of the loads. It is the friction of the piles that mainly providebearing capacity of the composite foundation. The friction of the piles grows with the growing of the piles but deceases when reaching the bottom the piles.