Numerical Analysis Of Stability Of Composite Reinforced Earth Abutment With Geogrid And Anchor

Reinforced earth abutment has many advantages,such as high strength,strong bearing capacity and excellent seismic performance.Because of its continuous flexible body,it can effectively solve the stubborn problem of bump at bridge head.Nevertheless,a single reinforced earth abutment still has some shortcomings,and it is difficult to build a single-stage reinforced earth abutment with abutment height above 10 m in engineering.In addition,laying geogrid in backfill soil to form reinforced earth abutment can only ensure the overall stability of the soil in the structure,but has no reinforcement effect on the structure itself and the filling behind it,which limits the application range of reinforced earth abutment and can only build reinforced earth abutment with abutment height below 10 m.In some projects with complex working conditions,special environment and harsh geological conditions,it is difficult for a single retaining structure and reinforcement measures to meet the needs of the project,and it is more effective to combine various reinforcement measures or retaining structures,such as composite reinforced soil abutment combined with anchor rods.In this paper,the safety factors of common abutments,reinforced earth abutments,anchored abutment and composite reinforced earth abutments combined with anchor rods under different heights are calculated by FLAC 3D finite element difference software,and the variation law of safety factors with the height of reinforced earth abutments is analyzed,and the height range of abutments suitable for various abutments is summarized.By establishing a control test,the safety factors and maximum strain increment nephogram of common abutment,reinforced soil abutment,anchor reinforced abutment and composite reinforced soil abutment at the same height are compared,and the effects of reinforcement treatment,anchor reinforcement and joint reinforcement of anchor and geogrid on improving the overall stability of abutment are summarized.Comparing the stress nephogram of the joint mechanism of anchor rod and geogrid with that of single geogrid and anchor rod,the mechanism of joint reinforcement of anchor rod and geogrid is summed up.The main conclusions of this paper are as follows:(1)With the increase of abutment height,the filling quality of abutment increases,the center of gravity of abutment gradually moves up,the lateral earth pressure of backfill and the bending moment of abutment to the bottom layer also increase,and the increase of lateral earth pressure and bending moment is the cause of vertical moving surface,i.e.overturning failure surface and circular slip surface,i.e.sliding failure surface;(2)No matter how many meters the abutment height is,the effect of joint reinforcement of geogrid and anchor rod on improving safety factor is greater than that of single reinforcement method.For reinforced earth abutments,only when the abutment height is less than 10 m,can the abutment safety after reinforcement have sufficient safety reserves;for anchored abutment,only when the abutment height is 5m,and for composite reinforced earth abutments combined with anchor rods,as long as the abutment height is less than 20 m,the abutment strengthened by geogrid and anchor rods has sufficient safety reserves,and the overall stability of the abutment is excellent.(3)When the abutment height is less than 20 m,with the increase of abutment height,the enhancement effect of reinforcement treatment on abutment safety factor is slightly weakened,while that of anchor reinforcement is strengthened,while that of geogrid and anchor joint reinforcement is almost unchanged and stable.(4)When the abutment height is more than 20 m,especially when the abutment height reaches 30 m,the single reinforcement,i.e.,anchor reinforcement and reinforcement treatment,has little improvement on the abutment safety factor,and the effect of improving the abutment stability is weak,while the joint reinforcement of geogrid and anchor is stil significant.(5)Compared with the single reinforced earth abutment and the abutment reinforced by anchor,the composite reinforced earth abutment combined with anchor has more advantages.The joint use of anchor and geogrid makes the stress distribution of geogrid more uniform,with little stress concentration,and the geogrid can be brought into full play.At the same time,the performance of anchor is also effectively brought into play,avoiding material waste.In addition,the joint reinforcement of anchor and geogrid greatly improves the overall stability of the abutment.