The Theoretical Calculation And Analysis On Bearing Performance Of Ram-compaction Multipile Expansion Pedestal Piles Under The Uplift Load

With the rapid development of society,the construction of transport facilities and high-rise building are essential.Therefore,the design and checking of the anti pulling engineering become one of the important research contents of the engineering construction.Ram-compaction Multipile Expansion Pedestal Pile,can greatly improve the bearing capacity.It’s mature technology of science and technology is reliable,pollute and cost are low.But as a new type of pile,the pile’s uplift mechanism is in the low level of understanding.Recognizing the bearing capacity transfer mechanism of rammed pile improving the theoretical study will be helpful to promote the popularization and application of the Ram-compaction Multipile Expansion Pedestal Pile.On the basis of reading and analyzing the relevant literatures at home and abroad,this paper studies the mechanism and bearing capacity of the Ram-compaction Multipile Expansion Pedestal Pile by theoretical calculation,prototype test,indoor model test and numerical simulation.There are:First,on the basis of the failure surface of the anti-piles,we assume the fracture surface of the pile,and use the ultimate balance method to derivate theoretical calculation formula of extreme uplift bearing capacityof the long pile(length to diameter ratio greater than or equal to 20)and short pile(length to diameter ratio less than 20)Second,the prototyping experiment is used to study the ultimate tensile capacity and pull-out mechanism of the pile.But the experimental data do not satisified the research requirements completely,so we do the indoor simulation test of straight shafe pile,single-head rammed pile,multi-head rammed pile in clay and sand.The results show that the multi-head rammed pile has a higher tensile capacity and less diaplacement than the straight shafe pile,single-head rammed pile.When the rammed pile is added to the ultimate load,the surface of the soil produces circular fractures,the soil failure is stripped as a compressive deformation-local plastic zone-overall shear failure.According to the results which obtained from the indoor experiment,the fracture surface of the multi-head rammed model pile is similar to the assumed fracture surface,and the calculated value of the bearing capacity is close to the measured value.Third,the FLAC 3D finite element simulation software is used to simulate the prototype test.We can obtain the simulation results,analyze the load transfer and deformation behavior of the Ram-compaction Multipile Expansion Pedestal Pile.When the pile is applied to the load,the pile straight section,the pile enlarged’s carrying capacity is gradually played.The enlarges share a part of the load.With the increase of the load value,the enlarges’ load ratio also increases.Then,we analyze the main factors of pullout failure mode,bearing capacity and provide a reference for its design.