Influence of bamboo fiber reinforcement on the mechanical behavior of soft soil

Soft soils, characterized by low strength and high compressibility, pose significant challenges to civil engineering projects, often leading to excessive settlement and structural instability. While fiber reinforcement is a known soil improvement technique, there is limited research on the application of natural materials like bamboo fiber for stabilizing high-plasticity clays. This study systematically investigates the influence of bamboo fiber on the unconfined compressive strength (UCS), apparent cohesion, and internal friction angle of a high-plasticity clay from Chittagong, Bangladesh. A comprehensive series of 63 unconfined compression tests (ASTM D-2166) and 63 direct shear tests (ASTM D-3080) were conducted on soil specimens reinforced with varying percentages of bamboo fiber (0% to 1.25%) and lengths (10 mm to 25 mm). The results demonstrate that bamboo fiber reinforcement has significant potential for ground improvement. The UCS increased by up to 75% and the apparent cohesion by a remarkable 195% compared to unreinforced soil, with optimal performance observed at a fiber content of 0.75% and a fiber length of 10 mm. This enhancement is primarily attributed to the "bridging effect" of the fibers, which creates a mechanical interlock that impedes the propagation of failure planes and enhances stress distribution. However, fiber lengths exceeding 10 mm led to a reduction in strength, which is interpreted as evidence of pull-out failures due to insufficient anchorage within the lab-scale specimens. While this research highlights the promise of bamboo fiber as a sustainable reinforcement material, it also underscores the critical role of optimizing fiber content and length. The study’s limitations, including its small scale and unaddressed long-term durability, necessitate further research to validate these findings for large-scale field applications.