Strengthening of high plastic clays by geotextile reinforcement

High plastic clays (fat clays) instigate failures like rutting and fatigue cracks in flexible pavements and sometimes make the pavements unserviceable when subjected to wet-dry cycles of the environment. This study focuses on the strengthening potential of polypropylene fiber (PP) on the engineering properties of fat clays. Different fiber percentages (0.2, 0.4, 0.6, and 0.8% by oven-dried soil weight) were used in clay samples and then compaction properties, unconfined compressive strength (UCS), elastic modulus (E50), California bearing ratio (CBR), and swell-consolidation properties of reinforced samples were investigated. Also, desiccation tests were carried out to assess the efficacy of fibers in enhancing the cracking resistance of clay. The test results show remarkable strength improvement, as the UCS value of 0.4% reinforced soil increased by 356%, E50 by 109%, and soaked CBR by 225%, resulting in a better-quality subgrade for pavement construction. The compression and rebound indices were decreased by 49.5% and 78.8% for fiber content of 0.8%, respectively, as well as the percent swell and swell pressure were also lowered by 75.4% and 70%, respectively, shifting the medium swelling soil to a low swelling class. Furthermore, the scanning electron microscopic (SEM) studies revealed that the frictional interface between fiber-clay particles appears to be the primary mechanism influencing the reinforcing effect. Economically, stabilizing fat clay reduces the required pavement thickness by an average of 38%. Hence, PP fiber as a low-cost material provides a long-term stabilizing solution for widespread fat clays.