scholarly journals Analysis of cylindrical cavity expansion in anisotropic critical state soils under drained conditions

2019 ◽  
Vol 56 (5) ◽  
pp. 675-686 ◽  
Author(s):  
K. Liu ◽  
S.L. Chen
Keyword(s):  
Cylindrical Cavity ◽  
Cavity Expansion ◽  
Induced Anisotropy ◽  
Cylindrical Cavity Expansion ◽  
Preconsolidation Pressure ◽  
Modified Cam Clay ◽  
Lagrangian Formulations ◽  
Parametric Studies ◽  
Stress Induced Anisotropy ◽  
Stress Patterns

This paper presents a semi-analytical solution for the drained cylindrical cavity expansion problem using the well-known anisotropic modified Cam clay model proposed by Dafalias in 1987. The prominent feature of this elastoplastic model, i.e., its capability to describe both the initial fabric anisotropy and stress-induced anisotropy of soils, makes the anisotropic elastoplastic solution derived herein for the cavity problem a more realistic one. Following the development by Chen and Abousleiman in 2013 of a novel solution scheme that establishes a link between the Eulerian and Lagrangian formulations of the condition of radial equilibrium, the plastic zone solution can eventually be obtained by solving a system of eight partial differential equations with the three stress components, three anisotropic hardening parameters, specific volume, and preconsolidation pressure being the basic unknowns. Parametric studies have been conducted to explore the influences of K0 consolidation anisotropy and overconsolidation ratio (OCR), and their pronounced impacts on the stress patterns outside the cavity as well as on the development of stress-induced anisotropy are clearly observed.

Drained solution for cylindrical cavity expansion in modified Cam clay soil under constant vertical stress

2020 ◽  
pp. 1-14
Author(s):  
D. Su
Keyword(s):  
Plane Strain ◽  
Cylindrical Cavity ◽  
Stress Condition ◽  
Vertical Stress ◽  
Plane Strain Condition ◽  
Cavity Expansion ◽  
Strain Condition ◽  
Cylindrical Cavity Expansion ◽  
Modified Cam Clay ◽  
Cam Clay

Cavity expansion is a fundamental theoretical problem in geomechanics. For the cylindrical cavity expansion problem, derivations of solutions are usually based on the assumption that the soil is subject to the plane strain condition. However, this is untrue for cavity expansion in pressuremeter tests. This study first derived the equilibrium equation for cylindrical cavity expansion under the constant vertical stress condition. Then, the equilibrium equation was solved for modified Cam clay soils with different overconsolidation ratios (OCRs). The solutions were compared with the responses in the same soils under the plane strain condition. It was found that the ratio of the limiting cavity pressure in the latter to that in the former ranged from 1.31 to 2.76 and increased with an increase in the OCR. Under the constant vertical stress condition, significant heaving occurred in the vicinity of the cavity, and volumetric strain evolved from contraction to dilation as the OCR increased. Significant differences were noted in the stress paths of the two different loading conditions. These results indicate that the assumption of the plane strain condition will lead to overestimation of the limiting cavity pressure and inaccurate prediction of the stress path in the pressuremeter test, especially for heavily overconsolidated soils.

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

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Mengxi Zhang ◽  
Xiaoqing Zhang ◽  
Chengyu Hong ◽  
Lalit Borana ◽  
Akbar A. Javadi
Keyword(s):  
Constitutive Model ◽  
Cylindrical Cavity ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Cavity Expansion ◽  
Induced Anisotropy ◽  
Shield Tunneling ◽  
Tunnel Excavation ◽  
Cylindrical Cavity Expansion ◽  
Deformation Area

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.

Dynamic finite cylindrical cavity-expansion models for cellular steel tube confined concrete targets normally impacted by rigid sharp-nosed projectiles

2021 ◽  
pp. 204141962110272
Author(s):  
Chaomei Meng ◽  
Dianyi Song ◽  
Qinghua Tan ◽  
Zhigang Jiang ◽  
Liangcai Cai ◽  
...  
Keyword(s):  
Cylindrical Cavity ◽  
Approximate Model ◽  
Steel Tube ◽  
Confinement Effect ◽  
Confined Concrete ◽  
Cavity Expansion ◽  
Depth Of Penetration ◽  
Cylindrical Cavity Expansion ◽  
Infinite Cylindrical Shell ◽  
Response Modes

Cellular steel-tube-confined concrete (CSTCC) targets show improved anti-penetration performance over single-cell STCC targets due to the confinement effect of surrounding cells on the impacted cell. Dynamic finite cylindrical cavity-expansion (FCCE) models including radial confinement effect were developed to predict the depth of penetration (DOP) for CSTCC targets normally penetrated by rigid sharp-nosed projectiles, and stiffness of radial confinement was achieved with the elastic solution of infinite cylindrical shell in Winkler medium. Steady responses of dynamic FCCE models were obtained on the assumption of incompressibility of concrete, failure of comminuted zone with Heok–Brown criterion and two possible response modes of the confined concrete in the impacted cell. Furthermore, a DOP model for CSTCC targets normally impacted by rigid projectiles was also proposed on the basis of the dynamic FCCE approximate model. Lastly, relevant penetration tests of CSTCC targets normally penetrated by 12.7 mm armor piecing projectile (APP) were taken as examples to validate the dynamic FCCE models and the corresponding DOP model. The results show that the DOP results based on dynamic FCCE model agree well with those of the CSTCC targets normally penetrated by rigid conical or other sharp-nosed projectiles.

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