Optimal mixing ratio and SWCC fitting of lightweight soil with cotton stalk fibres

Abstract

The application of lightweight soil for changing and filling is an effective foundation treatment method for the construction of sponge cities in collapsible loess areas. In this paper, the L25(54) orthogonal test targeting on the strength, permeability and density characteristics was first used to optimize the mixture ratio design of proposed lightweight soil with cotton stalk fibres (LSCF). The corresponding effects of each mixed content on the performance of LSCF were analysed. The soil water characteristic curves (SWCCs) of LSCF with different cement and cotton stalk fibre contents were then measured using the quick centrifuge method. In comparison with undisturbed loess, the volumetric moisture content of LSCF (for the same matrix suction) was larger, and LSCF had a better water-holding capacity. Based on the Van Genuchten model, an improved fitting model for matrix suction SWCC of LSCF was proposed by considering the influence of cement. Qualitative agreement with the test results indicates that the proposed model could be potentially used to obtain the SWCC curve without conducting any experiments, which is especially useful for the sponge city constructions in loess areas.