Investigation on soil water retention characteristics and tensile strength of phyllite residual soil reinforced with polypropylene fibers

This paper aims to evaluate the effects of polypropylene fibers on the water retention characteristics and tensile strength of phyllite residual soil, and to innovatively propose dual-peak soil water retention curve (SWRC) and tensile strength characteristics curve (TSCC) models, examining the influence of fiber content and initial void ratio across the full range of degree of saturation. Experimental results indicate that the SWRC of phyllite residual soil exhibits a distinct dual-step pattern, with a decrease in void ratio significantly enhancing water retention capacity. However, the addition of polypropylene fibers has a minimal impact on the SWRC, showing only slightly increases at the steps of the curve, with the SWRC at a fiber content of 0.2% being superior to that of 0.5%. The tensile strength displays a dual-peak variation trend across the full range of degree of saturation. At lower void ratio, the tensile strength of the soil is significantly improved. Moreover, the addition of polypropylene fibers markedly enhances the tensile strength, reaching an optimal point at a fiber content of 0.2%, after which the strength decreases due to fiber-soil particle aggregation and uneven fiber distribution. This research provides new insights into the performance of soil reinforced with fibers, thereby offering theoretical support for the practical application of reinforced soil in engineering projects.