Research Of Bearing Performance Of Pile With Expanded Branches And Plates For Highway Bridge

As the increasing requirement of the ultimate bearing capacity of the upperstructure upon single pile, ordinary straight rod piles cannot complete controlsettlement request. Squeezed branch pile is a new pile which based on the originaluniform-section pile process and a dedicated expansion device, squeezing stratum in acertain depth of the pile hole, formatting of cavity, and then pours concrete. Due to thestandard values of tip resistance is much higher than the frictional resistance, so infact, the superior bearing capacity of squeezed branch piles is from bearing capacityof plates within the length of the pile body everywhere. The good performances ofsqueezed branch pile in the field of civil, promoting the development in the high-wayfield. Structural characteristics of highway bridges and culverts’ squeezed branch pileembodied in a larger diameter and greater pile length, diameter of more than1.2m,the pile length of more than40m. Systematic studies on how the pile body structurechanges caused of the change of the bearing mechanism and bearing performance areinsufficiency at present.This paper is getting down to research under the background. This article deducesunder the crowded extrusion of expansion device, the final formation of the cavityprofile geometry is not a straight line, but hyperbolic segment and circular arc. Usingthe theory of elastic-plastic mechanics of soil, this paper deduces radius range ofplastic zone under certain extrusion expansion, and required pressure pushed to theradius.By on-site full-scale squeezed branch pile test of Shijiazhuang Hutuo riverextra-large bridge engineering and Ningbo city ring expressway in east section,measured pile variable under pile top load, transformed into axial force value, and getthe pile side friction, plate resistance, pile end resistance and the displacement of eachcross section through calculation of the axial force value processing, in order to studytheir development change rule. As the study shows that the bearing capacity ofbearing plate is gradually play from top to bottom, presents the alternating load effect,the bearing capacity of the upper plate plays the most complete, bottom plate plays incomplete. Relationship of load-settlement for bridges and culverts’ squeezed branchpiles varies gradually, compared with the straight pile, the higher bearing capacity,less settlement, the contributions of bearing plate on the pile ultimate bearing capacityis more than30%.The bearing capacity is improved by compacting effect on soil body of plates, inorder to quantitatively study on the increase degree, this article put forwards theinnovative concept of bearing capacity increase coefficient of plate’s soil body, whichis roughly between3.1and3.5through a pile test, and points out that the coefficient isassociated with plate’s soil texture, plate ring area and plate depth. This paper,combined with the original formula of bearing capacity, deduces a new calculationformula of bridges and culverts’ squeezed branch piles bearing capacity, whichprovide a reference to design and research of bridges and culverts’ squeezed branchpiles in future.