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

Chang, Ming-Fang; Teh, C. I.; Cao, Laifa

doi:10.1680/geot.51.4.335.39390

Cited by 19 publications

(8 citation statements)

References 13 publications

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“…For a 10 cm 2 cone with a radius of 17.85 mm with the standard penetration rate 20 mm/s, the strain rate of soil element at cavity wall is about _ ε a � 800000%/h based on the spherical cavity expansion theory. And the undrained shear strength interpreted from the piezocone test is 59% larger than that determined from the consolidated undrained triaxial test with the reference strain rate calculated from equation (38), which is consistent with the study of the scholar Chang et al [22]. e rate of shearing in the consolidated undrained (CU) triaxial test is usually chosen based on the pore water pressure equilibrium condition of the soil sample during the shearing process.…”

Section: Effect Of Penetration Ratesupporting

confidence: 69%

Prediction Method for Overconsolidation Ratio of Marine SoftSoil Based on the Piezocone Penetration Tests

Zhang

et al. 2019

Advances in Civil Engineering

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Because of the strong structural and sensitive behavior, the properties of marine soft soil change greatly when subjected to external disturbances, which leads to great difficulty in reflecting its real mechanical properties in the laboratory soil tests. The piezocone penetration test (CPTU) is one of the main technologies for in situ testing of geotechnical engineering. CPTU has the advantages of being fast and convenient, no sampling, low disturbance to soil, large amount of data, and reliable testing. The determination of the overconsolidation ratio (OCR) based on the CPTU results can solve the problems of soil disturbance and stress release, which occur during the consolidation test in the laboratory. However, there are still some problems such as lack of strict theoretical analysis of penetration mechanism and incomplete interpretation theory of in situ test parameters of CPTU. In this paper, the CPTU cone head is assumed to be hemispherical considering the penetration mechanism of CPTU. Moreover, the compaction modes of the CPTU probe penetrating into soil are adopted as spherical and cylindrical cavity expansion modes, respectively. The ultimate expansion pressures of the probe penetrating into soil under the spherical and cylindrical cavity expansion modes are first obtained by virtue of the theory of cavity expansion. Then, two prediction methods for OCR considering the roughness and penetration rate of the cone are proposed by combining the ultimate expansion pressures of the probe penetrating the approximate closed solution of cavity expansion in the modified Cambridge model, which is suitable for predicting the OCR of marine soft clay. Finally, to verify the reliability of the two proposed prediction methods, comparisons with the in situ CPTU tests of marine soft clay in two coastal areas and two existing prediction methods are made. The comparison results show that predictions of OCR of marine soft clay in this paper are close to Wayne’s method and more accurate than Chanmee’s method since the factors such as cone roughness and penetration rate are considered in the new proposed prediction methods. In order to improve the applicability in different cases of the OCR predictions, the average values of the two proposed methods are recommended as the reference value for the OCR of marine soft soil.

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Section: Effect Of Penetration Ratesupporting

confidence: 69%

Prediction Method for Overconsolidation Ratio of Marine SoftSoil Based on the Piezocone Penetration Tests

Zhang

et al. 2019

Advances in Civil Engineering

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“…The 0 consolidated clay is assumed to be linearly elastic and infinitesimal deformation until the onset of yield. Thus, according to the Hook's Law, the elastic stress-strain relationship can be expressed in the increment form as follows: where and are the elastic modulus and the shear modulus, respectively, which are defined in the 0 -MCC model as follows [6]:…”

Section: Constitutive Relationsmentioning

confidence: 99%

“…Theoretical analysis of cylindrical cavity expansion theory in geotechnical engineering has been widely used in pile sinking, shield tunneling, static cone penetration test (CPT), pressuremeter test (PMT), and mixing pile construction disturbance problems [1][2][3][4][5][6]. Hill (1950) first proposed the spherical cavity expansion method and derived a general solution of stresses and displacements in Tresca material [7].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Soil-Compacting Effect Caused by Shield Tunneling Using Three-Dimensional Elastoplastic Solution of Cylindrical Cavity Expansion

Zhang

Hong

et al. 2018

Mathematical Problems in Engineering

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Soil squeezing effect and formation disturbance caused by tunnel excavation can be simulated by cylindrical cavity expansion due to the comparability between tunneling and cavity expansion. Although most of the existing theoretical derivation is based on simple constitutive model of soil foundation, not only the relation between principal stress components was simplified in the solution process, but also the stress history, initial stress anisotropy, and stress-induced anisotropy of structural soil were neglected. The mechanical characteristics of soil are closely related to its stress history, so there is a gap between the above research and the actual engineering conditions. A three-dimensional elastoplastic solution of cylindrical cavity expansion is obtained based on the theory of critical state soil mechanics and engineering characteristics of shield tunneling. In order to fully consider the influence of initial anisotropy and induced anisotropy on the mechanical behavior of soils, the soil elastoplastic constitutive relation of cavity expansion is described in the course of K0-based modified Cam-clay (K0-MCC) model after soil yielding. An equation with equal number of variables is obtained under the elastic-plastic boundary condition based on the Lagrange multiplier method. By solving the extreme value of the original function, the analytical solution of radial, tangential, and vertical effective stresses distribution around the circular tunnel excavation is obtained. In addition, changes of elastic deformation area and plastic deformation area for soil during the shield excavation have been analyzed. Calculation results are compared with the numerical solutions which usually consider isotropic soil behavior as the basic assumption. In this paper, a constitutive model which is more consistent with the actual mechanical behavior of the soil and the construction process of the shield tunnel is considered. Therefore, the numerical solutions are more realistic and suitable for the shield excavation analysis and can provide theoretical guidance required for design of shield tunneling.

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“…In a cavity expansion approach is used to study the pore pressure dissipation after pile installation. Semi-analytical solutions based on critical state models are reported by Yu & Houlsby (1991), Collins et al (1992), Collins & Stimpson (1994), Cao et al (2001), Chang et al (2001) for the drained and undrained cylindrical expansion.…”

Section: Introductionmentioning

confidence: 99%

Assessment of Rate Effects in Piezocone Tests from Poroelastic Cavity Expansion Analysis

Dienstmann¹,

Maghous²,

Schnaid³

2018

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Cavity expansion solutions are often used in geomechanics modelling to investigate problems such as the bearing capacity of piles or interpretation of cone and pressuremeter tests. Conceived as a simplified approach to capturing the transient flow effects in the soil around an expanding cylinder, a non-linear poroelastic model is formulated in this paper based on the concept of proportional poroplasticity. The latter is used to assess rate effects and associated drainage conditions during piezocone penetration. In this context, cone tests performed in gold tailings at penetration rates ranging from 0.1 mm/s to 57 mm/s are used to validate the proposed approach. The model predictions are directly compared with in situ testing results in the space of normalized velocity V h to cone resistance Q and to degree of drainage U, demonstrating the model capability of capturing the transitions from drained to partially drained and undrained soil regimes.

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

Cited by 19 publications

References 13 publications

Prediction Method for Overconsolidation Ratio of Marine SoftSoil Based on the Piezocone Penetration Tests

Prediction Method for Overconsolidation Ratio of Marine SoftSoil Based on the Piezocone Penetration Tests

Analysis of Soil-Compacting Effect Caused by Shield Tunneling Using Three-Dimensional Elastoplastic Solution of Cylindrical Cavity Expansion

Assessment of Rate Effects in Piezocone Tests from Poroelastic Cavity Expansion Analysis

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