Characterization of inherent spatial variability of loess deposit properties in Shaanxi Province, China

Purpose: Inherent spatial variability of properties of loess deposit along depth direction plays important roles in soil reclamation, agricultural irrigation, and risk assessment and management of geo-hazards on the Loess Plateau. This study aims to develop a database for loess deposit properties in Shaanxi Province first, followed by evaluating and reporting comprehensively the abovementioned spatial variability along depth. Materials and methods: A comprehensive literature review and numerous laboratory tests were conducted for 37, 81, and 177 loess profiles respectively for sandy, silty, and clayey loess to examine their properties in Shaanxi Province, China. For each property collected in the database, the means, coefficients of variation (COV), most suitable probability distribution functions, and spatial correlation lengths along the depth direction were evaluated and reported. Results and discussion: The physical and index properties and strength properties of the three loess soil generally exhibit relatively low variabilities with a mean COV of less than 20.0% in most cases. In contrast, the deformation properties exhibit medium to high variabilities with a mean COV varying from roughly 27.0 to 85.0%. For all of these properties mentioned above, the spatial correlation length along depth was estimated to be approximately 3 ~ 8 m. Conclusions: (1) The COV of loess properties at one site can be significantly different from that at other sites. Thus, the site-specific variabilities of loess deposit properties shall be considered in geological design and analysis. (2) When site-specific data of properties for loess deposits are not available for on-going geological/geotechnical projects, the typical ranges of loess properties obtained in this study, including their statistics and correlation lengths, can be used as guidelines for approximation.