The effect of randomly distributed natural fibers on some geotechnical characteristics of a lateritic soil

Weak lateritic subgrades are more often than not encountered during road construction in Ghana. This makes it necessary to find economically efficient ways to improve the engineering properties of these marginal lateritic soils. The objective of this study is to investigate the effects of coconut fiber (30 mm, 60 mm and 90 mm fiber lengths) and palm fiber on some geotechnical characteristics of a weak lateritic subgrade. The lateritic soil was collected from the KNUST campus and blended with various percentages of the fibers varying between 0.1 and 1.0% by weight of dry soil. The mixed materials were then subjected to various laboratory tests including compaction, unconfined compression test and 4-day-soaked California bearing ratio test. From the results, it was observed that increasing the fiber content decreased the maximum dry density and increased the optimum moisture content. The inclusion of the fiber increased the soaked CBR from 7 to a maximum of 18, 22, and 25 at 30 mm, 60 mm and 90 mm fiber lengths, respectively. The unconfined compressive strength also increased from 140 to a maximum of 353 kPa, 398 kPa and 447 kPa, respectively, for 30 mm, 60 mm and 90 mm fiber lengths. Similarly, palm fiber inclusion recorded maximum soaked CBR value of 14% and UCS value of 352 kPa. These peak values were obtained at optimum fiber contents of 0.2%.