Cyclic loading tests on sandstone and limestone shale aggregates used in unbound forest roads

Abstract

This study examined the performance of two aggregates subjected to cyclic loading in a large-scale test rig. The two aggregates examined were: (i) a sandstone from Co. Cork, Ireland and (ii) a limestone shale from Co. Limerick, Ireland. The aggregates were classified and their engineering properties established and compared. Various depths of the aggregates, overlaying a 1-m-deep formation layer, were compacted and subjected to a cyclic loading regime of incrementally increasing pressures of 500, 750 and 1000 kPa. Each aggregate was tested for up to 150,000 load applications. The resilient pressures, resilient surface deflections and permanent deformations were measured. The sandstone performed well in a dry state but poorly when wetted up. The shale behaved poorly but the addition of a wet mix macadam (WWM) layer greatly improved its performance.