Undrained response of fibre reinforced expansive soil subjected to cyclic loading

Abstract

The evaluation of dynamic soil characteristics is a crucial task in understanding the geotechnical engineering problems associated with dynamic loads. Most of the investigations concentrated on non-expansive materials, and there is a dearth of information on the dynamic performance of fibre reinforced expansive soil. This research paper presents the experimental soundings on unreinforced and reinforced expansive soil with randomly distributed polypropylene fibre with varying confining pressures under cyclic loading. Furthermore, to understand the micro structural behavior of the fibre reinforced soil, samples are examined under SEM analysis after being subjected to cyclic loading. Quantitative analysis of soil micro pores was done through image processing. In addition, the study also included the presentation of maximum shear modulus, a modulus reduction curve and a pore pressure variation curve. Experimental results indicate that, the addition of fibres caused an improvement in the dynamic shear modulus and damping ratio with a rise in confining pressure. Inclusion of fibres reduces the permanent strain. The change of dynamic shear modulus and damping ratio over shear strain amplitude and the dynamic shear stress–strain curves were analyzed under different confining pressures. From the SEM analysis, fibre reinforced soil has a fabric with large packets of soil particles. Moreover, the presence of fibres enhanced pore distribution and diminished considerable amount of voids. The results of image processing shown the area porosity of unreinforced soil is 25.3% and that for 1% of fibre reinforced soil is 6.9%. This shows the enhancement of the interface effect of soil reinforced with fibre, which strengthens the soil and integrity.