Study On The Geocell Reinforced Treatment Method Of Differential Settlement At Bridge Approach Embankment

The bump at bridgehead caused by differential settlement at bridge approach embankment influences the comfortableness of driving,hinders the development of transportation,producs expensive maintenance and repair costs.This problem will become more and more serious because the number of bridges and culverts will increase with the further increase of highway grade and mileage in China.Geocell has strong lateral restraint,which can directly limit the lateral deformation of the soil filled in the grid.Considering that the application of geocell at increasing soil strength and reducing deformation in practical engineering is remarkable,it can be used to solve the problem of differential settlement at bridge approach embankment.However,the reinforced mechanism of geocell is lagging behind practice,what’s more,the effect of geocell in solving the problem of differential settlement at bridge approach embankment requires further study.Therefore,the strength properties of geocell reinforced soil,the interface resistance strength between geocell and coarse-grained soil and the effect of geocell in solving the problem of differential settlement at bridge approach embankment is studied through laboratory and ansys abaqus in the dissertation.This dissertation analyzes the cause of differential settlement at bridge approach embankment from the aspects of material property,environment,design and construction,and discusses the mechanism of the bump at bridgehead caused by differential settlement.The strength property of geocell reinforced coarse-grained soil is studied from the compactness of coarse-grained soil,the moisture content and the number of layers through the unconfined compression strength test.The interface resistance strength between geocell and coarse-grained soil is studied from the compactness of coarse-grained soil,the embedded length of geocell and the normal pressure through the pull-out test.At last,analysing the effect of solving differential settlement at bridge approach embankment by geocell in practical engineering.Based on the above research,the main conclusions are as follows:(1)The basic reason of differential settlement at bridge approach embankment is the stiffness difference between abutment and the road behind abutment.The settlemnet includes the compression settlement of sbugrade and the consolidation settlement of ground.Consolidation settlement often occupies the main part of settlement,and it takes a long time to complete consolidation.(2)The increase of the compactness of coarse-grained soil and the number of layers of geocell can improve the compressive strength of reinforced soil.The moisture content has little effect on the compressive strength of reinforced coarse-grained soil.Compared with two-dimensional geogrid and geotextile,the three-dimensional geocell has better effect on improving the compressive strength of coarse-grained soil.(3)The increase of the coarse-grained soil,the embedded length of geocell and normal pressure can improve the interface resistance strength between geocell and coarse-grained soil.And the influence degree of these three factors on the interface resistance strength is: normal pressure > the compactness of coarse-grained soil > the embedded length of geocell.(4)The computed result of finite element modeling shows that the stress field and displacement field in the bridgehead road are changed by the geocell reinforced bridgehead subgrade.The settlement of the road gradually chanced from zero next to abutment to the maximum far away from the abutment after reinforcement,which avoids the problem of differential settlement because of the integral settlement of bridge approach embankment.