Geogrid Reinforcement for Stiffness Improvement of Railway Track Formation Over Clay Subgrade

Abstract

Weak subgrade condition generally develops large settlements in ballasted tracks, leading to adverse performance. To ameliorate such problems, a commonly adopted technique is to provide a thick cushion of granular subballast/blanket over the subgrade. Owing to scarcity of natural resources, this is often a costly proposition. In the present study, application of geogrid reinforcement for possible reduction of the subballast thickness has been explored through large model plate load tests. The investigations include both single and multiple layers of reinforcement in the subballast. With geogrid reinforcement, stiffness and resiliency of track beds were found to have increased markedly. Optimum depth of single-layer geogrid in the subballast giving maximum performance improvement was about 0.33 times the loading diameter. The corresponding improvement in stiffness of the track bed was about 77%. With multiple layers of geogrid in the subballast, the improvement in stiffness was as high as 99%. It is observed that with just one layer of geogrid in the subballast, its thickness can be reduced by 33% (i.e., from 600 to 400 mm).