Effectiveness of RAP-Infused Granular Piles for Soft-soil Improvement

Abstract

The increasing demand for infrastructure development on suboptimal soils, particularly soft clays, has necessitated innovative ground improvement techniques. This study evaluates the effectiveness of Recycled Asphalt Pavement (RAP)-infused granular piles in enhancing the load-bearing capacity and settlement performance of soft clay beds. Utilizing both Ordinary Floating Granular Piles (OGP) and Encased Floating Granular Piles (EGP) with geotextile, a series of load-settlement tests were conducted to assess their suitability for soft soil reinforcement under varying mix proportions. The results reveal that the integration of RAP with stone aggregates significantly improves the mechanical properties of soft soils, with the optimal performance achieved using a 50% Stone - 50% RAP (50S-50R) mixture. This configuration demonstrated the highest ultimate bearing capacity and minimal settlement, effectively balancing the stiffness and strength of stone with the energy absorption and flexibility of RAP. Furthermore, the use of geotextile-enclosed granular piles (EGP) markedly enhanced performance by minimizing lateral bulging, optimizing load distribution, and further reducing settlement, with the 50S-50R (EGP) configuration achieving the most superior results. Comparative analysis indicates that configurations with higher RAP content (e.g., 75R-25S and 100R) are less effective due to the inherently lower stiffness of RAP; however, their performance improves significantly when combined with geotextile. This underscores the critical role of geotextile in enabling more effective load transfer and settlement control, particularly for sustainable construction practices. Overall, this research establishes RAP-infused granular piles, particularly when combined with geotextile enclosures, as a viable and sustainable solution for enhancing the load-carrying capacity of soft soils. The findings contribute to the advancement of geotechnical engineering by providing evidence-based insights into the use of recycled materials for ground improvement, promoting both environmental sustainability and economic efficiency in construction practices.