Experimental Study on Behaviour of Clayey Sand Reinforced by Polypropylene Fibre

Abstract

AbstractIn this paper, the author presents the improvements in the mechanical properties of clayey sand soils reinforced by polypropylene (PP) fibres. PP fibres with 3 different lengths of 10, 15 and 20 mm were mixed with the soil with content by weight of 0.5, 1 and 1.5%. Three types of experiments were conducted including 30 compaction tests, 30 direct shear tests and 10 triaxial compression tests. With the same compaction energy, the maximum dry density was achieved with a fibre length of 20 mm and a fibre content of 1%. After determining the optimum water content for each type of fibre length and content, the soil samples in the direct shear and triaxial compression test were prepared by compaction to have the corresponding maximum density. The direct shear test showed that as the fibre content or the fibre length increased, the cohesion c increased whilst the friction angle φ decreased. The cohesion c reached the maximum value with the fibre length of 20 mm and the fibre content of 1%. This value was 9 times greater than that of c of the un-reinforced soil. In the consolidated undrained (CU) triaxial test, the peak deviator stress was significantly improved compared to un-reinforced soil. The maximum values of both cohesion cCU and friction angle φCU were achieved with a fibre length of 15mm and a fibre content of 1%. The largest value of cCU of the reinforced soil was more than 10 times of the unreinforced soil. However, φCU did not have much improvement compared to un-reinforced soil.KeywordsFibre-reinforcedTriaxial testCompaction testPolypropylene fibre