A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions     

Pin-Qiang Mo  Xin-Wei Gao  Wenbo Yang  Hai-Sui Yu 《国际地质力学数值与分析法杂志》2020,44(7):1053-1076

A cavity expansion–based solution is proposed in this paper for the interpretation of CPTu data under a partially drained condition. Variations of the normalized cone tip resistance, cone factor, and undrained-drained resistance ratio are examined with different initial specific volume and overconsolidation ratio, based on the exact solutions of both undrained and drained cavity expansion in CASM, which is a unified state parameter model for clay and sand. A drainage index is proposed to represent the partially drained condition, and the critical state after expansion and stress paths of cavity expansion are therefore predicted by estimating a virtual plastic region and assuming a drainage-index–based mapping technique. The stress paths and distributions of stresses and specific volume are investigated for different values of drainage index, which are also related to the penetration velocity with comparisons of experimental data and numerical results. The subsequent consolidation after penetration is thus predicted with the assumption of constant deviatoric stress during dissipation of the excess pore pressure. Both spherical and cylindrical consolidations are compared for dissipation around the cone tip and the probe shaft, respectively. The effects of overconsolidation ratio on the stress paths and the distributions of excess pore pressure and specific volume are then thoroughly investigated. The proposed solution and the findings would contribute to the interpretation of CPTu tests under a random drained condition, as well as the analysis of pile installation and the subsequent consolidation.  相似文献   

Undrained cavity expansion in anisotropic soils with isotropic and frictional destructuration     

Mo  Pin-Qiang  Chen  Haohua  Yu  Hai-Sui 《Acta Geotechnica》2022,17(6):2325-2346

This paper proposes a semi-analytical solution of undrained cylindrical cavity expansion in anisotropic soils with both isotropic and frictional destructuration. The rigorous derivation based on the general form of the SANICLAY model with destructuration is provided following a standardized solving procedure, and the features of anisotropy and structuration are then invoked in the cavity expansion solution by adopting the non-associated hierarchical model. Cavity expansion tests in both structured and unstructured clays with various overconsolidation ratio are conducted to investigate the evolutions of effective stresses, excess pore pressure, anisotropic parameters and structuration factors during cylindrical expansion. The results show that the effective stresses at the cavity wall are lower after expansion and the cavity excess pore pressure is oppositely higher in structured clays with slightly smaller plastic regions. The evolutions of anisotropy for structured clays appear to follow similar patterns to unstructured cases, whereas the degree of anisotropy is further developed with gradual loss of inter-particle bonds. Finally, the proposed solution is applied to predict the limit pressure of pressuremeter tests in Bothkennar clay, showing its ability for interpretation of in situ testing data in natural structured clays.

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