The paper reports on aspects of an extensive research programme, including full-scale field trials and large -scale laboratory tests, to investigate the performance of geogrid reinforced pavements over voids. In the field trials 3m and 5m diameter voids were introduced into an 8m square test bed. Geogrids were placed over the areas to be voided and the 600mm deep pavement, which was constructed using Type 1 sub base material, was surcharged to a level of 5kN/m2. The laboratory tests were used primarily to study the effects of varying void diameter (ranging from 2m to 4m) and the number of layers of geogrids. The strains developed (together with creep strains and deflections) were measured by means of a novel strain monitoring system for a period of up to 4 days following the void formation. A tentative design procedure is proposed, based on the extensive experimental study.
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