Evaluation of the spatial variability characteristics of the unsaturated clay in Hefei, China

Abstract

Soil properties (or parameters herein) vary randomly in space because of different depositional conditions. The knowledge of the spatial variability characteristics of unsaturated soils can be critical to the reliability assessment of geological and geotechnical engineering problems such as the stability analysis of unsaturated soil slopes and the seepage analysis of earth dams. To investigate the spatial variability characteristics of unsaturated soils, the soil parameters, including physical, deformation, and hydraulic properties, are measured through laboratory tests in this study. It is found that the variability of the physical parameters is smaller than that of the deformation parameters, and smaller than that of the hydraulic parameters. Five existing methods are adopted to evaluate the horizontal and vertical auto-correlation distances that measure the spatial variability, and it is found that the space average method and the correlation function method are more suitable for evaluating the auto-correlation distances when the number of test data is small. To further explore the spatial variability characteristics, the Wilcoxon rank analysis is conducted, and the results show that the auto-correlation distance is an inherent property of soils and there is little difference among the results obtained based on the physical, deformation, and hydraulic parameters of the unsaturated soils.