Abstract
Soft soil generally has a high water content, and the accurate quantification of its mechanical parameters is an important aspect of foundation design and disaster prevention. The mechanical parameters of soft soil have significant spatial variability or heterogeneity due to the complex deposition process of soil, leading to the high uncertainty of the quantifications of its parameters. Therefore, understanding the spatial variability of the parameters is an important approach to reduce uncertainty. In this study, the high-resolution (0.1 m) tip resistance (qc) and side friction (fs) of 18 soft soils in coastal areas were measured using the Dual-bridge CPT in-situ test. The vertical and horizontal variabilities of qc and fs were investigated using the random field theory. The results showed that both qc and fs are stationary and ergodic. The coefficient of variation of vertical fs is much higher than that of qc. On the one hand, fs may be vulnerable to noise, and its test accuracy is lower than qc; on the other hand, it may be that the spatial variability of the residual strength of soft soil may be greater than that of its failure strength. The horizontal correlation distance and coefficient of variation of qc and fs have no obvious change trend along the depth direction, but compared with the coefficient of variation curve, it was found that the change trends of qc and fs are basically the same, which is considered to be related to the properties of the soil layer. The research results can provide support for the spatial variability evaluation and reliability analysis of soft-soil engineering in this area. At the same time, it can also provide a theoretical basis for the layout of exploration engineering and sampling spacing.
Highlights
Received: 27 December 2021The soft-soil layer is widely and thickly distributed in China; it has the characteristics of a high water content, low density, low strength, high compressibility, low permeability and medium sensitivity
Soft soil is generally characterized by a high water content, low shear strength and high compressibility, such that it is difficult to obtain an undisturbed sample, which makes it difficult to study the spatial variability of their parameters through laboratory tests
This paper systematically studied the evaluation method of the spatial variability of geotechnical parameters based on random field theory
Summary
The soft-soil layer is widely and thickly distributed in China; it has the characteristics of a high water content, low density, low strength, high compressibility, low permeability and medium sensitivity. Soft soil is generally characterized by a high water content, low shear strength and high compressibility, such that it is difficult to obtain an undisturbed sample, which makes it difficult to study the spatial variability of their parameters through laboratory tests. Cone penetration tests (CPT) are a high-precision in-situ testing technique that enable continuous and rapid testing They are an ideal method to study the parametric random field characteristics of soft soil. The study of the random field model parameters of fs is of practical importance To this end, this paper takes the coastal soft soil in northern Jiangsu, China, as an example; based on the qc and fs data of the cone penetration test, this paper studies its spatial variability using the random field theory, and discusses the random field model parameters and their variation laws in the vertical and horizontal directions, respectively. The research results can provide parameter support for the reliability analysis of soft-soil engineering in this area
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