Undrained cavity expansion in modified Cam clay I: Theoretical analysis

Abstract

This paper presents an analysis of the undrained expansion of a cavity in modified Cam clay. The problem is formulated in small strain in the elastic zone and large strain in the plastic zone. Exact closed-form solutions of the effective stresses around the expanded cavity are presented. Closed-form expressions for the excess pore water pressure and the total stresses have also been derived based on a simplified assumption regarding the shear stress variation around the cavity. The analytical solution shows clearly the influence of the overconsolidation ratio on the excess pore water pressure induced by cavity expansion. As both the excess pore water pressure and the cavity pressure are expressed explicitly in terms of the primitive modified Cam clay parameters, the solutions may provide a theoretical basis for the interpretation of in-situ tests such as the piezocone test and the pressuremeter test.

Evaluation of Smear Zone Extent Surrounding Mandrel Driven Vertical Drains Using the Cavity Expansion Theory

“…Collins and Yu (1996) and Cao et al (2001) proposed an analytical model of the cylindrical undrained cavity expansion assuming the yielding soil to obey the modified Cam-clay model. In this paper, the extent of the smear zone caused by mandrel driving into soft soil strata is determined on the basis of Cylindrical Cavity Expansion analysis.…”

“…For the benefit of the readers, a summary of the theoretical background is given in this section (Cao et al, 2001). Fig.…”

Undrained cavity expansion in modified Cam clay II: Application to the interpretation of the piezocone test

“…Note that equations (27) and (28) are respectively the same as equations (26) and (27) in the companion paper (Cao et al, 2001). This de®nition results in in®nite shear strain when the radial strain is in®nite or when the cavity is expanded from zero radius.…”

“…9 in the authors' companion paper (Cao et al, 2001), where r p aa u at the elastic±plastic boundary varies from 3 (at R 10) to 8 (at R 1 X 1) (corresponding to å 1 f values between 2´47% and 0´13%), equation (24) would give the equivalent strain rate å 1 varying from 0 X 0826 s À1 (at R 10) to 0 X 004 36 s À1 (at R 1 X 1). If one compares these rates with 1% per hour ( 2 X 8 3 10 À6 s À1 ), quoted by the authors as a regular strain rate in triaxial compression tests, one gets from their equation (3) s u as à u ratios varying from 12% (for R 1 X 1) to 15% (for R 10), which is much less than the 59% quoted by the authors.…”

Undrained cavity expansion analysis with a unified state parameter model for clay and sand

“…Cao et al (2001) presented an analysis of the undrained expansion of a cavity in modified Cam clay, by applying small strain in the elastic zone and large strain in the plastic zone. More recently, further semi-analytical solutions for undrained and drained expansions of cylindrical cavities in modified Cam clay soils have been reported by Chen & Abousleiman (2012) and Chen & Abousleiman (2013).…”