Study On Three-Way Load Bearing Characteristics Of In-slope Bridge Piles By Model Experiment And Numerical Simulation

With the development of "The Belt and Road" and "Western Development" strategy in depth,the rapid development of urbanization and industrial construction of our country,more and more bridges,electric power pylons and high-rise buildings will be constructed.Because of the restrictions of engineering geological conditions and environmental protection,some foundation piles have to set up on the slope.Compared with the conventional flat slope pile,because of the restrictions of the engineering geology and road alignment,the slope foundation pile will be subjected to three dimensional combined load,which leads to the bearing characteristics and failure mode of the slope foundation pile is more complex.On the other hand the current calculation theory of pile foundation design based on the combination of single plane loads is very difficult to accurately reflect the actual stress condition of slope foundation pile,which may bring inconvenience or even a security risk to the slope pile design.Therefore,it is of great engineering significance to study the force and deformation characteristics and failure modes of the bridge piles under the three direction combined loads.The paper mainly uses the method of model test and numerical simulation to carry out the research on the three-way bearing capacity of bridge pile foundation in slope section and obtains the following main results:.(1)In an actual prototype pile,according to the similarity theory,designed and completed at different load levels and slope angle of the slope laterally loaded pile experiments indoor model group,had a measured load-displacement curve and the pile top pile moment distribution.The results show that the horizontal displacement of pile top increases nonlinearly with the increase of slope,decreases linearly with the increase of horizontal load angle,and the maximum bending moment of pile body lies in the range of 3?5 times of pile diameter below the mud surface.Numerical simulation results show that the law of pile top displacement and bending moment distribution agree well with the indoor model test results,and the errors of internal force and displacement are controlled within 20%,which shows that the finite element method described in this paper can accurately simulate the horizontal bearing capacity of pile foundation and the feasibility of pile-soil interaction.(2)The effects of slope gradient,horizontal load angle,pile diameter,aspect ratio and sand mass on the bearing behavior of pile foundation and the interaction between pile and soil are studied by numerical simulation.The calculation results show that the influence of slope slope and pile diameter on the stress and deformation of the pile is the most obvious,and the effect of horizontal load angle is relatively small.However,the influence of aspect ratio and soil mass is negligible.The maximum bending moment of the pile body and the maximum ultimate soil resistance position are the same,and they move downward with the increase of the slope and the horizontal load angle,and appeared at 2 to 5 times of pile diameter below the mud surface,while pile diameter,aspect ratio and sand the influence of severe on the maximum bending moment of the pile and the soil resistance of the pile side can be neglected.(3)Taking a practical project as an example,according to the method of fixed displacement ratio loading,the failure model of ultimate bearing capacity of bridge piles under inclined load is established.The results show that the variation of the envelope curve of bridge piles with different slope loads is different from that of the traditional ground piles.The influence factors such as pile diameter,slope gradient and space load angle had little effect on the overall trend of the envelope of ultimate bearing capacity in two-dimensional load space.However,with the increase of pile diameter and the angle of horizontal load,the envelope of foundation pile tends to expand outward,while the envelope shrinks inwardly with the increase of slope gradient.The above conclusions can provide guidance for the design and construction of bridge piles in slope sections.