Analysis Of Horizontal Bearing Capacity And Reliability Of Bridge Piles In Slope Ground

With the development of the national economy and the promotion of " the Belt and Road"strategy and the "13th Five-Year Plan",highway engineering and railway engineering of China have achieved unprecedented development.Although large-scale traffic engineering has greatly facilitated people’s life,some of the high-speed or railway bridges need to be built on slopes.Especially in western China,because of the numerous high mountains,some bridges have to be built on canyons or even cliffs in order to meet the requirements of linearity,environment and cost.At this time,how to build high quality bridge foundation piles under the premise of the consideration of safety and environmental protection has become a key technical problem that restricts the sustainable development of highway or railway in mountainous area of China.However,what changes in the force and deformation of the slope will be caused by the existence of the force bearing and deformation mechanism of the slope piles and the slope gradient.How to determine the value of geotechnical parameters.How to calculate the reliability of the slope piles.These are all the key to solving these problems.In view of this,domestic and foreign scholars have made a lot of research on the slope piles,and some useful research has also been obtained.Therefore,on the basis of the existing research,this paper further develops the indoor model test,theoretical analysis and reliability evaluation method of bridge foundation piles of slope section under the effect of horizontal loading to investigate the influence of slope gradient and horizontal load effect angle on proportional coefficient m of the force coefficient,deformation and foundation resistance coefficient of the bridge foundation piles of slope section.Finally,the horizontal bearing reliability and influencing factors of the bridge foundation piles of slope section were studied.First of all,the indoor model test of the bridge foundation piles of slope section under horizontal load is carried out,and the law of the change of the stress,deformation and the ratio coefficient m of slope bridge foundation piles with the slope and the angle of the horizontal load action is discussed.The test results show that the larger the slope and the angle of horizontal load action,the greater the horizontal displacement of piles top and the maximum bending moment of piles body,and the greater the calculation error.The increase of the slope and the angle of horizontal load action leads to that the ratio coefficient m of the foundation of slope section is obviously smaller than that of flat foundation.Secondly,the bearing characteristics of the bridge foundation piles of slope section under horizontal load were analyzed,and the simplified force model considering the slope effect and horizontal load angle was established.The corresponding flexural differential equation and finite difference solution were deduced,and the corresponding MATLAB program was compiled,and then compared the calculation results with the test results to verify their applicability.Then,taking the actual project as an example,according to the slope foundation piles model considering the slope effect and the internal force calculation method,the effects of slope gradient,pile diameter and elasticity modulus of the foundation piles on the internal force and displacement of the foundation piles are discussed.The results show that both the bending moment of pile body and the horizontal displacement of pile top increase with the increase of slope gradient.When the slope gradient is increased from oO to 60。,the maximum moment increase amplitude of pile body is between 21%and 25%,the increase amplitude of horizontal displacement at the top of pile is as high as 80%.The influence of elasticity modulus on the bending moment of pile body is smaller,but on the horizontal displacement of pile top is greater.lf the elasticity modulus increases by 10,the increment amplitude of the bending moment of the pile is between 3%and 10%.The angle of horizontal load action has smaller effect on the bending moment of pile.If the angle of horizontal load action is increased from Oo to 90“,the increase amplitude of horizontal displacement of pile top is about 45%.Finally,the basic methods of reliability calculation and their respective advantages and disadvantages and applicable situation are introduced.Based on the stochastic response surface method,the reliability calculation method of horizontal loaded slope foundation piles is established,and the corresponding program is compiled.Then the applicability of the method is verified by calculation examples.On this basis,the influence of pile diameter,elasticity modulus of pile body,ratio coefficient m of foundation resistance coefficient and horizontal load on the reliability index of bridge foundation piles of slope section is analyzed.The analysis found that the pile diameter and the pile elastic modulus have a greater influence on the yield model of the pile body material.The pile diameter,the pile elastic modulus,the ratio coefficient m of the foundation and the horizontal load on the top of the pile will cause the decrease of the reliability index under the failure mode of the horizontal displacement of the pile body at the ground.The pile diameter,the pile elastic modulus and the ratio coefficient m of the foundation have a greater influence on the reliability index of the pile body coner failure mode at the ground.In actual engineering eonstruction and inspection,the indexes with high influence factors should be strictly controlled and targeted prevention measures should be taken to ensure the safety of foundation piles.