Experimental And Numerical Simulation Study On Bearing Characteristics Of Bridge Pile Foundation In Slope Section Under Horizontal Cyclic Loading

Compared with the ordinary plain pile foundation,the stress environment of bridge pile foundation in slope section is more complex,and the dynamic response caused by vehicle braking load,seismic load and wind load is more obvious.In the design of bridge pile foundation in slope section,if the influence of this dynamic load is ignored,it is bound to bring safety hazards and risks to the operation of the bridge.Therefore,based on the research results of others on slope pile foundation,this paper further explores the influence of horizontal cyclic load on the bearing characteristics of bridge pile foundation in slope section by quasi-static method.Firstly,the stress of the bridge pile foundation in the slope section is analyzed,and the transfer matrix solution for the calculation of the internal force and displacement of the pile body is derived.The relationship between the proportional coefficient of the slope foundation and the slope is measured through the indoor model test,and then the influence of the slope gradient and horizontal load on the internal force and displacement of the bridge pile foundation in the slope section is analyzed.Secondly,the model test of bearing characteristics of bridge pile foundation in slope section under horizontal cyclic load is carried out.Based on the test phenomenon,load-displacement curve,pile bending moment distribution and horizontal load distribution,the influence of slope gradient,cycle number and loading grade on the horizontal bearing characteristics is discussed.Finally,through numerical simulation,the test model is established to verify the test results.Based on the actual project,the influence of pile diameter and pile spacing on the bearing characteristics of bridge pile foundation in slope section is analyzed.The main research results of this paper are as follows:(1)The proportional coefficient of slope foundation decreases nonlinearly with the increase of slope gradient;the horizontal displacement of pile top and the maximum bending moment of pile body increase with the increase of slope gradient and horizontal load of pile top.When the slope gradient increases from 0° to 60°,the horizontal displacement of pile top increases by about 86.4%.When the horizontal load of pile top increases by 50kN,the horizontal displacement of pile top increases by 48.5%on average,and the maximum bending moment of pile body increases by 41.6%on average.(2)The increase of slope gradient will weaken the stability of soil around the pile and weaken the horizontal bearing capacity of bridge pile foundation.With the increase of the number of cycles,the maximum bending moment and the percentage of horizontal load bearing of the front row pile gradually increase when the bridge pile foundation in the slope section is loaded forward,and the horizontal bearing effect is mainly borne by the front pile.When the bridge pile foundation in the slope section is subjected to negative loading,the maximum bending moment of the front row pile and the percentage of horizontal load bearing decrease gradually.When the loading displacement amplitude exceeds 15mm,the main bearing object of horizontal load changes from the front row pile to the back row pile.(3)The horizontal bearing capacity of bridge pile foundation in slope section increases with the increase of pile spacing and pile diameter in a certain range,and the load is mainly borne by the pile section in the range of 8 times the diameter below the pile top.