Study On The Mechanical And Deformation Characteristics Of High-fill Arch Culvert Of Expressway

High fill culverts are common in mountainous highways.With the continuous improvement of highway mileage in mountainous areas,the number of high fill culverts to be built under the highway is also increasing.The linear earth pressure theory in the current general specification for highway bridge and culvert design cannot accurately reflect the vertical earth pressure and strain law of culvert top,and its calculation results do not match the actual stress of culvert,which may lead to different degrees of diseases during culvert construction,use process and extreme geological disasters.In addition,the mechanism of interaction between culvert structure and soil is easily neglected in design,which leads to the continuous occurrence of culvert diseases.Through theoretical analysis and numerical simulation,this paper respectively explores the influencing factors and variation rules of stress deformation and displacement of high fill arch under filling and earthquake,and achieves the following results:(1)The diseases of culvert with high filling are mainly caused by additional stress caused by differential settlement of soil inside and outside the top soil layer of culvert,which makes the pressure on the top of culvert greater than the dead weight of soil.With the continuous increase of filling height,the deformation of filling soil gradually tends to be stable,and the settlement difference between culvert top and culvert side is gradually reduced.When the filling reaches a certain height,the settlement of culvert top and the settlement of culvert side are equal to each other at a certain height,i.e.an equal settlement surface appears.The vertical earth pressure at the top of culvert increases with the increase of filling height and the coefficient of soil pressure concentration increases continuously.However,when the filling at the top of culvert reaches a certain height,the coefficient of soil pressure concentration at the top of culvert tends to be stable gradually and shows a tendency of slow decrease.(2)According to the results of finite element calculation,five factors affecting the soil pressure concentration coefficient at the top of culvert are explored.The research shows that the internal friction angle of filling and the Poisson ratio of filling have relatively large influence on the soil pressure concentration coefficient at the top of culvert.The stress at the top of culvert can be dispersed by reducing the internal friction angle of filling or reducing the Poisson ratio of filling.By establishing orthogonal test with six factors and five levels and using range analysis method,the influence degree of six factors on soil pressure concentration coefficient at the top of culvert is calculated as follows: internal friction angle of filling soil > width of Valley > Poisson ratio of filling soil > cohesion of filling soil > foundation modulus >elastic modulus of filling soil.(3)The stress and displacement of culvert body and arch ring will change significantly when high filling arch culvert is subjected to earthquake at different filling heights.Due to the increase of filling height of soil body,the relative displacement of culvert top and foundation bottom surface decreases gradually,and the change period of dynamic response of displacement will be extended,but the total displacement of each monitoring point of arch ring is increasing constantly.In practical engineering,when designing arch culvert in valley area with high seismic incidence,the filling height can be reduced appropriately to prevent large displacement of arch ring under seismic condition and to improve the anti-overturning ability of culvert.At the same time,the stress at each monitoring point of culvert body and arch ring is gradually increasing.The increments of effective stress and shear stress at both ends of culvert foundation are more obvious,and the increments of axial force,shear force and bending moment at the arched toes at both ends of the arch ring are significant.(4)The stress and displacement of culvert body and arch ring will change gradually under the action of seismic excitation when high filling arch culvert is subjected to different peak acceleration earthquakes.With the increase of peak acceleration,the peak internal force at each monitoring point of the arch ring and the peak internal force of the arch ring gradually increases,and the increments of axial force,shear force and bending moment are obvious under the seismic intensity of M 8to M 9.At the same time,the horizontal displacement of the vault and the relative displacement of the vault and the base surface also show an increasing trend.Therefore,when designing the arch culvert with high seismic requirement,the arch foot and bottom angle of both sides of the foundation should be reinforced to prevent damage caused by high seismic intensity.