Study On Dynamic Characteristics Of Pier Piles In High Slope Under Earthquake Action

In recent years,with the advance of "the Belt and Road" strategy and “the Development of the West”,in order to solve the transportation problems and protect the ecological environment,the high and steep slope bridge road in the mountains become a trend.At the same time,as most of China is under the threat of strong earthquakes,many lines have frequent earthquakes,which seriously threaten the operation and use of bridges and people’s life and property safety.But there isn’t clear specification about bridge pile foundation in the high slope on the seismic design at the moment.Therefore,in order to provide some experience and reference value in this paper,the bearing mechanism and deformation characteristics of pier piles under the influence of high slope vibration displacement were studied due to earthquake action.The main contents and conclusions of this paper are as follows.(1)Using the one-dimensional elastic theory of soil and the Winkler beam foundation theory,the dynamic expressions for displacement and internal force of the double pier piles built in high slope were obtained,and the dimensionless variation curves of the displacement and internal force of the pier pile under corresponding engineering conditions were obtained.The curve results show that the horizontal displacement of front and rear piles decreases with the increasement of height,but the horizontal displacement of front piles is larger in the whole.The bending moments of two piles have a similar trend,which increases first and then decreases as the height of position increases.The shear stress of front pile changes in a wavy shape,but generally decreases with the increasement of height,while the shear stress of rear pile decreases first and then increases.(2)Based on FLAC3 D numerical simulation software,a three-dimensional space model was established after considering the nonlinearity of soil and interaction of pilesoil.The results show that the horizontal displacement of front and rear piles decreases with the increasement of height,because they are connected by cap at the top of piles.The axial force of two piles changes in a parabolic way,and there is a great difference between the two piles at the same height.The shear stress variation of two piles has a similar trend in the half lower,and the bending moment of two piles also has this change,but in the half upper,the trend is basically inconsistent.The shear stress of soil at a certain depth below the surface of the slope is small,the horizontal displacement is stratified from the bottom regularly,and there is obvious uplift at the shoulder of the slope and the front slope of the front pile.(3)By changing the design parameters of pier piles,such as the diameter of piles,the length of piles,the elastic modulus of piles and the ratio of the distance between two rows to diameter of piles,the influence of different factors on the shear stress of slope section,the displacement and internal force of pier piles and the shear resistance between pile and soil was investigated.The change of the ratio of distance of two rows to diameter of piles has little influence on the deformation and internal force of pier piles and slope,while the diameter of piles,the length of piles,the elastic modulus of piles can improve the influence of earthquake on the slope and pier pile in a certain range,but when they increases to a certain value,the effect is not obvious.(4)Comparing the parameters analysis of numerical simulation based on the fourth chapter with the parameters analysis of theoretical calculation based on the second chapter,the increase of the diameter of piles,the length of piles,the elastic modulus of piles changes the correlation coefficient of the displacement and internal force formula,thus it causes changes in displacement and internal force of the pile piers.In the theoretical calculation,the curves of displacement and internal force of pile varies more relaxed.