Impact of repeated loading on mechanical response of a reinforced sand

Mirzababaei, M ORCiD: 0000-0002-4801-8811Pavements constructed over loosely compacted subgrades may not possess adequate California bearingratio (CBR) to meet the requirements of pavement design codes, which may lead to a thicker pavementdesign for addressing the required strength. Geosynthetics have been proven to be effective for miti-gating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-baselayers in road construction. This study investigated the behaviors of unreinforced and reinforced sandwith nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading). Thedepth and number of geotextile reinforcement layers, as well as the compaction ratio of the soil aboveand below the reinforcement layer(s) and the compaction ratio of the sand bed, were set as variables inthis context. Geotextile layers were placed at upper thickness ratios of 0.3, 0.6 and 0.9 and the lowerthickness ratio of 0.3. The compaction ratios of the upper layer and the sand bed varied between 85% and97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testingscenarios. Repeated CBR loading tests were conducted to the target loads of 100 kgf, 150 kgf, 200 kgf and400 kgf, respectively (1 kgf¼9.8 N). The results indicated that placing one layer of reinforcement with anupper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97%significantly reduced the penetration of the CBR piston for all target repeated load levels. However, usingtwo layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97%with upper and lower thickness ratios of 0.3 resulted in the lowest penetration