Study On Load Bearing Characteristic Of Squeezed Branch And Plate Pile With Full-Scale Test And Numerical Methods

To increase the bearing capacity of pile, many researches design many kinds ofspecial figure pile, for example, the enlarged diameter pile, enlarged bottom pile anddifferent section pile. The squeezed branch and plate pile is a type of special figure pile.It is based on the straight pile, squeezed soil around pile to form branch or plate with ahydraulic squeezed machine. The branches and plates enlarge the surface of pile andchange a part of friction resistance into end resistance and increase the pile bearingcapacity. Because of the higher bearing capacity, lower settlement and lower pollutionto environment, it is widely used in recent years.The squeezed branch and plate pile is a new type of pile, study on its theoretical isnot further than the practice. At present, it mainly used in vertical pile in industry andcivil constructions, the study is concentrated on test and project application. Manystudies are carried out on degree of influence of pile parameters itself, but in fact, thesoil parameters around pile influence the bearing capacity of pile most. Base on theresult of home and abroad and situ test, the mechanics of squeezed branch and platepile is study in this paper with FEM method. The main work includes:Firstly, base on the full-scale test data of three squeezed branch and plate piles,the load transfer mechanism is analyzed, the friction resistance or equivalent frictionresistance change with the settlement of pile is analyzed. Predicate the load bearingcapacity of pile with hyperbola method, fitting Q-s curve of every part of pile withhyperbola curve. The results indicate that the hyperbola method is effective inpredicting the bearing capacity of squeezed branch and plate pile.Secondly, under vertical load test, the parameters of soil around pile such asinternal friction angle, cohesion, friction factor of pile-soil interface and Young'smodulus ratio of pile and soil, soil strata distribution. Analysis the pile bearing capacity,pile top settlement, axial load transfer along pile depth, distribution of frictionresistance and stress in soil under pile end. Influence degree of sediment thicker underpile end and mud thicker aside pile to the pile bearing capacity, the result can bereferenced by pile design and construction. Thirdly, using three dimensional FEM method, under the condition of concretepile and steel are liner, soil around pile is elastic-plastic, analysis the influence of plateposition, plate number, plate diameter, plate distance, pile diameter, pile length, soilcohesion, internal friction angle, Young's modulus, soil strata distribution to the pilelaterally load beating capacity.Fourthly, consider the initial stress field and concrete damage, infinite elementand finite element couple, no-linear caused by crack of concrete, couple interactionbetween concrete and steel, elastic-plastic of soil around pile, no-linear contact ofinterface between pile and soil, plastic deformation of pile body, pile lateraldisplacement, soil displacement behind pile, pile moment, shear, stress along pile side,steel stress, relative displacement between pile and soil, vertical and laterallydisplacement front pile.Lastly, analysis the influence degree of plate positions, pile distance, pile numbereffect to the pile displacement, pile moment, pile shear, relative displacement betweenpile and soil, laterally displacement and stress distribution between two piles tobearing capacity of every pile in pile group. Consider initial stress field, nonlinearcontact between pile side and soil, pile bottom and soil, cap and soil.