Study On Failure Mechanism And Structure Optimization Of Gully High Fill Culvert

High-filled culverts account for a large proportion of high-grade highways in mountainous areas.The construction of high-grade highways in mountainous areas will inevitably increase the amount of excavation and filling.The current high-filled culverts generally have the problems of high cost,many diseases,and difficult maintenance.By studying gully high-filled culverts,the height of the top filling of the culvert is reduced,and the depth of the bottom filling of the culvert is increased.The influencing factors of the culvert’s stress are reduced,thereby reducing the stress complexity of the culvert.Therefore,the research on the destruction mechanism and auxiliary structure design of high-filled culverts in gullies is of great significance to practical engineering.Aiming at the above problems,this paper applies the large-scale finite difference software Flac 3D to numerically simulate the maximum vertical displacement of the bottom fill of the gully high-filled culvert under different working conditions,and obtain the mechanism of deformation and failure.The auxiliary structure at the bottom is optimized,and finally the effect is evaluated.The conclusion is as follows:(1)The behavior of the maximum vertical displacement value of each monitoring point of the bottom fill of the culvert with zero gully slope at different filling heights was studied.The connection of the maximum vertical displacement values of the monitoring points of the culvert underfill is a concave curve,and the range of depression is 1/3～1/2 of its total depth,and the degree of depression is proportional to the total depth of the fill.The maximum vertical displacement at the exit is smaller than at the entrance,and the difference between the two increases with depth.(2)The behavior of the bottom fill of culvert under the influence of gully slope after maximum settlement was studied.When the slope of the gully at the bottom of the culvert is less than 20%,the connection of the maximum vertical displacement values of the monitoring points at the bottom of the culvert is a concave curve.When the slope is 0%,the lowest point of the concave curve is almost in the middle of the culvert.As the slope increases,the lowest point gradually moves toward the exit of the culvert.When the slope is between 20% and 30%,the maximum vertical displacement values of the monitoring points at the bottom fill of the culvert are connected as a slope,and the slope is approximately the same as the slope of the gully.The slope of the gully is that with the increase of the slope(0～30%),the vertical value of the maximum displacement of the filling at both ends of the culvert changes from the original outlet less than the inlet to the outlet greater than the inlet,and the difference increases continuously.(3)The effect of the proportion of the length of the excavation at the bottom of the culvert over the entire culvert length on the maximum vertical displacement of the culvert was studied.Culverts that are at the criticality of filling and digging,1/5digging,1/4 digging,1/3 digging,and 1/2 digging have the same slope at the bottom gully slope of 10%,20%,and 30%,respectively.The vertical displacement values are approximately the same,so their proportion has no significant effect on the maximum vertical displacement of the culvert.(4)The relationship between the point where the maximum vertical displacement value of the bottom fill is generated after the culvert is supported and the two points closest to the point where the maximum vertical displacement value is zero is studied.After the culvert is supported at the exit,the maximum vertical displacement value at the bottom of the culvert corresponds to the centerline point B of the culvert,the point A closest to the point B in the inlet direction is zero,the point A closest to the point B in the outlet direction The point C of the displacement value is zero,and the horizontal distance relationship between the three is: BA=(BC)*(3.5～4.5)The difference in fill height between the two ends of the culvert has little effect on this value.If multiple support points are set,the ratio between the first support point and the junction between the fill and excavation will have a greater impact,which is reduced by 10 %～20%.(5)When the slope of the gully at the bottom of the high-filled culvert of the gully is not 0,only one support point is set.After the support,the soil settlement at the left and right ends of this point is greater than when it is not supported,so it is on the semi-filled and semi-excavated foundation The culvert must have at least two support points.When the length of the culvert is not greater than 25 m,the two support points should be located at three-quarters of the length of the culvert and the exit of the culvert.In addition to setting support points at the entrance and exit of the culvert,the number of support points in the middle of the culvert on the fully-filled foundation should also consider the material properties of the culvert body.(6)The width range of the culvert bottom supporting structure was studied.The width of the support structure at the lower part of the culvert is at least greater than the width of the foundation of the culvert.The specific value should be based on the width and nature of the filling on both sides of the culvert in the actual project,and the dragging effect of the filling on both sides of the supporting structure should be minimized.This paper systematically analyzes the influencing factors and failure forms of high-filled culverts in gullies and deeply studies the failure mechanism of high-filled culverts in gullies.According to the optimization of the auxiliary structure at the bottom of the culvert,the optimal layout plan for the lower auxiliary structure of the gully with high filling culvert was obtained.