Study On The Capacity Of Single Cast-in-Situ Piles With Expanded Branches And Plates

Cast-in-situ piles with expanded branches and plates is a new style of pile which is widelyused in recent years. Based on piles with a constant section, this style of piles is with varioussection through constructing some expanded branches and plates in the suitable strata of soils.The vertical load capacity of a single pile is mainly took on by the expanded branches and plates.These piles can take full use of the potential capacity of soils surrounding piles, prove themechanical property of soils and elevate the capacity of soils nearby the branches and plates.Therefore, the capacity of pile per 1m3 concrete is raised by times. Compared with other ordinarycast-in-situ piles, this style can save raw materials, lower the construction cost effectively,shorten construction time. So, this new style of piles is provided with high social and economicbenefit.This dissertation discus the effect of distance, shape, magnitude of expanded branches andplates to the capacity of single piles, based on the data obtained form analysis to factualengineering case using the finite element method program THGEA. Several effect figures areplotted. The optimum expanding angle, optimum magnitude of expanded branches and optimumvertical distance of branches are proposed through the analysis to those figures.The analysis shows that, the expanding angle ought to be in between 60°～90° and 70° is theoptimum. The suitable distance of is no less than 6 times of the pile diameter and no more than 3times of the branch diameter. When there is soft underling stratum, the thickness of hard stratumbelow the branches must be more than 6 times of the pile diameter. The more of magnitude ofbranches, the higher of capacity of the pile. But this does not suggest that infinite branchesshould be constructed. Too more branches can lengthen the constructing time, harm the qualityof boring and result in disturbance to other branches. Moreover, the congruence effect of soilscould undermine the capacity of branches because of too more branches constructed. Therefore,in order to obtain the maximum capacity of branches, it is necessary to consider the capacity ofsoils and the critical distance of each branch comprehensively.