Experimental Study on Geocell-Stabilized Unpaved Shoulders
Two-lane highways often consist of aggregate or turf shoulders, which require maintenance on a recurring basis. Rutting and edge drop-offs are the most common performance problems. The maintenance of unpaved shoulders is typically done by placing and compacting more geomaterial. This practice is considered temporary and does not address the cause of the problem; therefore, the problem often recurs. On the other hand, the typical materials used for constructing shoulders contain little organic matter, which makes vegetation growth on these shoulders difficult. Vegetation on the shoulder can prevent erosion due to water runoff and wind, thus it is desirable to maintain a healthy vegetation cover on the shoulders. The previous study showed that an aggregate and topsoil mixture had the same ability to sustain vegetation as a topsoil. The addition of the topsoil into the aggregate lowered the strength of the aggregate, thus geocell could be used to improve the performance of the mixture. This study aimed to evaluate the performance of aggregate, aggregate-topsoil mixture, and geocell-stabilized aggregate-topsoil mixture as the geomaterials for constructing shoulders. Three large-scale cyclic plate loading tests were conducted on sections of 200 mm thick base courses over 5% CBR subgrades (moderate subgrade). The base courses consisted of: (a) 200 mm thick aggregate, (b) 200 mm thick aggregate-topsoil mixture, and (c) 50 mm thick aggregate-topsoil mixture over 150 mm thick geocell-stabilized aggregate-topsoil mixture. The total and permanent deformations of the base course surface under the loading plate were monitored by the actuator. The permanent deformations were used to evaluate the performance of different test sections.
KeywordsAggregate Base course Geocell Performance Unpaved shoulder
This research was sponsored by the Kansas Department of Transportation (KDOT). Mr. Jonathan Marburger was the project monitor at KDOT. Presto Geosystems supplied the geocell used in this study. Hamm Inc. from Perry, Kansas supplied the AB-3 aggregate material. Mr. Byron Whitted and Mr. Lee Crippen, the undergraduate research assistants at the University of Kansas, provided great assistance to the experimental tests. All the above support and help are greatly appreciated.
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