Investigation of compaction and shear resistance of soil reinforced with PP fibers

Abstract

This study examines the impact of Polypropylene (PP) fibers on clayey sand soil reinforcement. The experimental soil consisted of a mixture of 70% sand and 30% silt and clay, with PP fibers of 10, 15, and 20mm in length. The fibers were mixed into the soil in three weight ratios of 0.5%, 1%, and 1.5%. Initially, the reinforced soil was tested for compaction to determine the optimal moisture content and maximum dry density for each combination of fiber length and ratio. Next, direct shear tests and CU triaxial compression tests were conducted on maximally compacted samples based on the compaction test results. The preparation of materials and experimental samples followed a meticulous and strict process to create samples with fibers evenly distributed in volume and direction. The results showed a significant increase in soil parameters such as maximum dry density, cohesion, and friction angle in the direct soil shear test when PP fibers were mixed with clayed sand. The maximum deviatoric stress and corresponding strain in the CU triaxial compression test also increased. These parameters reached their highest value when the fiber content was 1% and the fiber length was 15mm to 20mm. However, if the fiber content was high (1.5%) and the maximum fiber length was 20mm, the above parameters would give the smallest value.

Keywords: Fibre-reinforced; triaxial test; compaction test; polypropylene fiber; direct shear test.