Research On Bearing And Deformation Behavior Of Batter Piles Under Combined Horizontal Load And Torque

In recent years,battered piles have been widely used in engineering foundations such as offshore wind turbines,offshore terminals and UHV transmission towers.The axis of battered pile is not perpendicular to ground plane,and the lateral soil pressure and displacement of soil around pile shaft are non-axisymmetric distribution,which makes the bearing deformation behavior of battered pile more complex than straight pile.For the UHV battered pile of transmission tower,it is often subjected to horizontal loads,torque and vertical loads from the wind and superstructure.When the vertical load generated by the superstructure is relatively small,the complex combined effect caused by the wind load which are simplified to the horizontal load H and the torque T on the top of the battered pile will significantly affect the bearing capacity of battered piles.Therefore,studying the bearing deformation behavior of battered piles under combined horizontal load and torque has important engineering practical significance on the design of battered piles.Firstly,the bearing deformation behavior of model piles which were embedded in sandy soil and subjected to combined horizontal load and torque were studied in indoor tests.The influence of the inclined angle of the pile shaft and the roughness of pile-soil interface on the ultimate torsional bearing capacity,the torque,the bending moment and the shearing force of pile shaft were analyzed.The results show that: under the combined load,the battered piles suffer torsional failure.The larger the inclination angle of battered piles,the greater the reduction of ultimate torsional bearing capacity,and the larger the roughness,the increasement of ultimate torsional bearing capacity.Besides,torque of battered piles are been distributed along the full length of the pile shaft.While bending moment and shear force of battered piles are mainly been distributed in a certain depth range under the pile top.Then,the numerical method was used to simulate the bearing and deformation behavior of construction single battered piles which were embedded in cohesive soil and subjected to combined loads.What's more,the effect of pile shaft inclined angle on the lateral displacement of pile shaft,the torque and bending moment of pile shaft was investigated.Moreover,the influence of the pile-soil stiffness ratio,load eccentricity and length-diameter ratio on the ultimate torsional bearing capacity were discussed.The results show that: under the combined load,the battered piles suffer torsional failure.The larger the inclination angle of pile shaft,the greater the increase of ultimate torsional bearing capacity.Besides,torque of battered piles are been distributed along the full length of the pile shaft.While bending moment of battered piles are mainly been distributed in a certain depth range under the pile top.What's more,the length-diameter ratio of pile shaft has significant influence on the ultimate torsional bearing capacity for battered piles compared with pile-soil stiffness ratio and load eccentricity.With the increase of length-diameter ratio,the ultimate torsional bearing capacity of pile shaft increases greatly.Finally,the numerical method was used to analyze the bearing and deformation behavior of 1×2 battered pile group in cohesive soil under the combined loads,and the bearing and deformation behavior of 1×2 battered pile group under the horizontal load or torque were compared.The results show that: compared with the battered pile group only subjected to torque alone,the distribution of the torque along the shaft of piles subjected to combined loads are obviously different,which causes the pile shaft to bear unequal torque.Morever,compared with the battered pile group only subjected to horizontal load alone,the combined loads will cause the unequal allocation of the shear force and the bending moment at the pile head,and causes the pile shaft to bear unequal bending moment.