Water retention behaviours of intact and recompacted loess exposed to multiple wetting-drying cycles

Abstract

Wetting-drying cycles of weathering loading frequently lead to failure of infrastructures in loess regions, China. Water retention behaviours of loess are key information for capturing the physical causes of loess engineering problems. To demonstrate variations in water retention performance of intact and recompacted loess from three regions due to a purely environmentally driven deterioration process, laboratory testing programmes were carried out to measure soil water retention curve (SWRC) and microstructure, by incorporating employing a pressure plate apparatus and scanning electron microscope. According to the laboratory results, the wetting-drying weathering has a significant impact on the water retention properties of intact and recompacted loess, especially after the first wetting-drying cycle. A distinctive feature was that the SWRC of the intact loess was bimodal, whereas that of the recompacted loess was unimodal. The features of water retention behaviour and its variations as well as linking with soil microstructure were well interpreted by the conceptual model, considering multiple influences including wetting-drying cycles, soil fabric and regional variability. A new equation was proposed to provide a unified description about the water retentions of both intact loess with bimodal behaviour and recompacted loess with unimodal characteristics. The parameters were able to define the variables of SWRC, and it was highly usefulness and effectiveness in terms of external environmental influences, such as multiple wetting-drying cycles, soil fabric, regional differences and soil types.

Keywords

loess / water retention behaviour / weathering loading / wetting-drying cycles / soil fabric

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