Impact of repeated loading on mechanical response of a reinforced sand

Pavements 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

Effect of cell height and infill density on the performance of geocell-reinforced beds of Brahmaputra River sand

© Springer Nature Singapore Pte Ltd 2020. Geocells, which are three-dimensional interconnected cells, are laid over foundation bases to provide lateral confinement to the infill material and thus improve the load-bearing capacity of the bases. Some experimental and mathematical studies have been reported in the literature in this regard. In this research, a laboratory experimental program was undertaken to study the improvement of bearing capacity of geocell-reinforced granular bases made from Brahmaputra river sand. In a laboratory model test, a steel tank was filled with Brahmaputra river sand, reinforced with geocell of different heights (made from woven geotextile), and progressively loaded to record the load versus settlement response. The infill density of sand was also varied to evaluate the effect on performance of geocell-reinforced sand beds. A square steel plate placed on the geocell-reinforced sand bed was incrementally loaded till failure to quantify the positive effects of geocell height and density of infill soil on the resultant bearing capacity. Enhancement of bearing capacity of geocell-reinforced sand bed with the increase in geocell height and density of infill material was evident from the test results. The bearing capacity of the geocell-reinforced bed, as compared to an unreinforced bed, is found to be increased by 1.8–4.3 times for normalized height of 0.33–1, having infill soil relative density of 70%, and 4.3–8.6 times for normalized height of 0.33–1, having infill soil relative density of 90%. The test results also show that significant reduction of settlement is achieved by the use of geocell reinforcement