Comparative Study On Horizontal Bearing Capacity With Variable-section And Equal-section Pipe Piles

The horizontal bearing performance of variable-section pipe pile isstudied based on the Nation Natural Science Fund Project（51208194）“study of the single pile bearing capacity of the ladder-type precastconcrete pipe pile and the key technology of adapter”.Through two largescale model tests, theoretical analysis, the horizontal bearing capacity ofvariable-section pipe piles and equal diameter pipe piles is constrastivedunder horizontal loads bearing behavior.（1）Through large-scale model test, three different variable diameterratio variable-section pipe piles and two equal diameter pipe piles ofdifferent diameter load-time-horizontal displacement curve、load-horizontal displacement curve, load-displacement gradient curveand tensile stress/strain curve of pile body under transverse static load areobtained. On the basis, the m-horizontal displacement and bendingmoment distribution of pile body are found. The analytical results are asfollows: with same external diameter of the upper half body outsidediameter piles, the bigger of the lower half body diameter pile is, the pilebearing capacity increases the level of the second half of the pile with aslight increase in the diameter of the pile; Under the same averagediameter of pipe piles, the level of the variable cross-section pile bearingcapacity were greater than equal diameter pipe pile horizontal bearingcapacity, increase the bearing capacity by30%; The pile bending momentof variable-section pipe piles have2peaks, which are located on the upperand lower halves of the pile, the peaks of the upper half of the pile isbigger than the lower half of the piles’; the location of pile bendingmoment of the variable-section pipe pile is higher than the equaldiameter’s.（2） The changing law of proportion coefficient of horizontalresistance coefficient are analysed based on horizontal load test results.And through the regression analysis, the foundation of horizontalresistance coefficient proportional coefficient m and the horizontaldisplacement of pile top are established. The research results show thatthe horizontal displacement of the pile head is small, pile top horizontal displacement on the horizontal resistance coefficient of the influence onproportion coefficient, and when the displacement of pile top level morethan a certain threshold, the proportion of the horizontal resistancecoefficient of coefficient hardly changes over horizontal displacement ofpile top.（3）The calculation formula of internal force and displacement ofpile top of the variable cross-section pipe pile are established based on mmethod, which confirmed the rationality and feasibility of the establishedanalysis method.