Study On The Stress Characteristics Of Highway Culvert And Calculation Of Reinforcement Load Reduction In Mountain Areas

Rigid and flexible culverts under embankments in mountainous areas are widely used in highway projects.Although the culvert structure is simple,the interaction between filling and structure is complex,and culvert roof cracking often occurs in engineering.At present,most studies agree that the factors affecting the earth pressure at the crown of culvert are the difference of settlement between internal and external soil columns,but the assumption that vertical sliding surface is used at the interface between internal and external soil columns is still to be discussed.Geogrid and EPS slab can effectively reduce the earth pressure on culvert top,but their theoretical analysis is generally scattered,and there is no theoretical calculation method for the combination of the two after load reduction.In addition,the stress characteristics of shallow buried pipelines are significantly affected by external temperature,and the research on the stress characteristics of pipelines under different freeze-thaw modes is relatively less.In view of the above two shortcomings,this thesis studies the calculation of earth pressure of high fill culvert and the characteristics of pipe culvert in frozen soil area.The main conclusions are as follows:Firstly,based on the relationship between filling and earth pressure of culvert,the method of reinforcement and load reduction of Geogrid and EPS plate is put forward,and the change of interface angle between internal and external soil columns caused by the difference of plane settlement above culvert is analyzed.The numerical simulation shows that the angle between the displacement contour of culvert crown fill with and without load reduction measures and the vertical direction is about 20 degrees,and the inclination is opposite.Secondly,indoor model tests are carried out to investigate the effect of thickness and density of EPS slab with flexible filler on the earth pressure load reduction at culvert crown and culvert side.At the same time,the combined load reduction of EPS slab and geogrid is analyzed.Based on the limit equilibrium theory and considering the angle between the interface of the soil column inside and outside the culvert crown and the vertical plane,the formula for calculating the earth pressure on the culvert top after load reduction by the "reinforced bridge" method is derived,which includes the earth pressure on the upper surface of the grille with the dip of the interface under three load reduction conditions,the analysis of the deformation and stress of the grille,the design of the grille(height,number of layers,length)and the calculation of the earth pressure on the flexible filling and the culvert crown.Finally,according to the geological conditions of frozen soil area and the freeze-thaw failure mode in practical engineering,through the Shallow-buried model test of PVC pipes in temperature control laboratory,the variation laws of stress and strain of pipes,soil pressure around pipes and deformation of pipes under different filling loads,different freeze-thaw modes and geogrid reinforcement conditions are obtained.The test results provide a reference for engineering design,construction and maintenance in the future.