An Examination of the Use of Geogrid as a Compaction Aid
MONTANA STATE UNIV MISSOULA
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Evidence from experimental and field applications suggest that the presence of geogrid in highway base course increases the ability of a granular material to compact. The addition of a geogrid into an aggregate base layer may decrease the lateral spreading of the base material as compaction effort is applied, leading to a greater potential for the base course to compact vertically. The hypothesis being examined is that given an equal amount of compactive effort, geogrid reinforced base course material can achieve a greater density than non-reinforced base course. This hypothesis was evaluated by the construction of test sections with and without geogrid, compaction of these test sections using small field-scale equipment, and measurement of density and void ratio by various means. The effects of varying lift thicknesses and compactive efforts were also evaluated. Changes in density were recorded with a nuclear densometer. A Dynamic Cone Penetrometer DCP was also used to indicate relative density of the base course. The third procedure for evaluating density and void ratio versus depth was accomplished via computer aided tomography CAT. CAT combines ordinary X-ray technology with sophisticated computer signal processing and delivers digital images capable of being analyzed with selected software. The software was then used to calculate a series of void ratios for soil samples taken from the reinforced and non-reinforced sections. An average void ratio for each section was then computed and the results for each reinforced and non-reinforced section compared. Based upon review of density results and DCP measurements, there does not seem to be a clear indication that geogrid reinforced base course material achieves a greater density than non-reinforced material given the same amount of compactive effort. The void ratios obtained via CAT scan analysis do show a better distinction between the two configurations.
- Civil Engineering