STUDY ON SOFTENING CONSTITUTIVE MODEL OF SOFT ROCK USING STRAIN SPACE BASED UNIFIED STRENGTH THEORY

2009 ◽  
Author(s):  
LI SONG ◽  
CHONGDU CHO ◽  
SHENG LU ◽  
HONGJIAN LIAO
Keyword(s):  
Constitutive Model ◽  
Soft Rock ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Strain Space

STUDY ON SOFTENING CONSTITUTIVE MODEL OF SOFT ROCK USING STRAIN SPACE BASED UNIFIED STRENGTH THEORY

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5375-5380 ◽  
Author(s):  
LI SONG ◽  
CHONGDU CHO ◽  
SHENG LU ◽  
HONGJIAN LIAO
Keyword(s):  
Constitutive Model ◽  
Constitutive Equations ◽  
Strain Softening ◽  
Soft Rock ◽  
Elastoplastic Strain ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Softening Behavior ◽  
Simulation Results ◽  
Strain Space

This study attempts to modify the unified strength theory by considering compression as a positive load in geotechnical engineering. It also aims to establish a unified elastoplastic strain softening constitutive model which can accurately describe the strain softening behavior of one kind of soft rocks distributed in Japan. The hardening function parameters of the unified elastoplastic strain softening constitutive model are determined from experiments. In addition, numerical simulations of this model are performed to compare the pre-peak, post-peak and the residual strengths of soft rock predicted by this study and experimental results. Simulation results demonstrated that the proposed constitutive equations in strain space can well describe the softening behavior and accurately predict the peak and residual strengths of soft rock. While the proposed equation is applicative for normally consolidated state and overconsolidated state according to the simulation results.

A Nonlinear Constitutive Model for Soil under Complex Stress State

2013 ◽  
Vol 535-536 ◽  
pp. 561-564 ◽  
Author(s):  
Hang Zhou Li ◽  
Hong Jian Liao ◽  
Bo Han ◽  
Li Song
Keyword(s):  
Constitutive Model ◽  
Principal Stress ◽  
Friction Angle ◽  
Complex Stress ◽  
Complex Stress State ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Strain Behavior ◽  
Chang Model

It is fundamental to predict the stress-strain behavior of soils to control the stability of the geotechnical engineering. A Duncan-Chang constitutive model is analyzed and found that it ignores the effect of the intermediate principal stress. A unified strength theory is investigated and revised. The lode parameter is introduced into the unified strength theory. The unified friction angle and cohesion which may reflect the influence of the intermediate principal stress and verified by the polyaxial tests are obtained. The compressive strength revised from the unified strength theory is used to replace the Mohr-Coulomb criterion and introduced into the Duncan-Chang model. A modified constitutive model is proposed, which is verified by the plane strain tests. The result shows that the modified constitutive can reflect the effect of the intermediate principal stress, and the Duncan-Chang model is a special case of the modified model when b=0.

Constitutive Model of Strain Softening for Soft Rock

2011 ◽  
Vol 250-253 ◽  
pp. 1932-1935
Author(s):  
Song Li ◽  
Hong Jian Liao ◽  
Hang Zhou Li
Keyword(s):  
Constitutive Model ◽  
Strain Softening ◽  
Three Dimensional ◽  
Soft Rock ◽  
Unified Strength Theory ◽  
Softening Behavior ◽  
Proposed Model ◽  
Deviatoric Plane ◽  
Modified Equation ◽  
Rock Specimens

This paper aims to study the strain softening behavior of soft rock. A modified equation of unified strength theory is proposed that is convenient to be applied in geotechnical engineering where compression is customarily taken as positive. And also the limit line on deviatoric plane of this modified equation is derived and introduced into the three dimensional (3D) elastic viscoplastic constitutive model of Yin and Graham. Parameters of the model are determined from experiments of the diatom soft rock specimens. Numerical simulations are performed to compare the strain softening behavior predicted in this paper and triaxial experimental results. Simulation results show that the proposed model can accurately describe the strain softening of soft rock.

The Development and Implementation of Improved Duncan-Chang Constitutive Model in ABAQUS

2011 ◽  
Vol 99-100 ◽  
pp. 965-971
Author(s):  
Zhi Ping Dai ◽  
Cheng Zhao ◽  
Chun Feng Zhao
Keyword(s):  
Constitutive Model ◽  
Principal Stress ◽  
Deformation Behavior ◽  
Fine Sand ◽  
Intermediate Principal Stress ◽  
Strength Theory ◽  
Unified Strength Theory ◽  
Dense Sand ◽  
Improved Model ◽  
Chang Model

As it ignorance the effect of intermediate principal stress, traditional Duncan - Chang model has limitation when applied into geotechnical engineering. It was improved through incorporating the effect of intermediate principal stress based on unified strength theory. Under the help of customized modification platform in ABAQUS, the applicability and stability of the improved model and the reliability of subroutine were validated through simulation of several examples. The results show the improved model can better reflect the deformation behavior of soil through taking the influence of intermediate principal stress into consideration. The improved model in paper can be applied into dense sand, fine sand and clay.

scholarly journals Effect of Intermediate Principal Stress on the Bearing Capacity of Footings in Soft Rock

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1019
Author(s):  
Zongyuan Ma ◽  
Faning Dang ◽  
Hongjian Liao
Keyword(s):  
Constitutive Model ◽  
Bearing Capacity ◽  
Strain Hardening ◽  
Principal Stress ◽  
Numerical Solutions ◽  
Soft Rock ◽  
Intermediate Principal Stress ◽  
Rock Foundation ◽  
Unified Strength Theory ◽  
Bearing Capacity Factor

The bearing capacity for footings is a fundamental scientific problem in civil engineering. The evaluation of the bearing capacity of footings usually does not take into account the effect of the intermediate principal stress. In practice, the intermediate principal stress has certain influences on the strength of geomaterials (e.g., rock and soil) or concrete. In this paper, a series of numerical solutions are presented to evaluate the bearing capacity of footings in a soft rock foundation via a two-dimensional finite difference code (FLAC) with a strain hardening/softening constitutive model based on the unified strength theory (UST). The values of the bearing capacity factor Nc and Nγ for strip, circular and square footings in a soft rock foundation were evaluated using the strain hardening/softening constitutive model. The effect of the intermediate principal stress on the bearing capacity of strip, circular and square footings in a soft rock foundation was analyzed. The results of the numerical computation show that the intermediate principal stress has a significant influence on the bearing capacity and failure mechanisms of a soft rock medium. The influence of the intermediate principal stress on the peak and residual values of the bearing capacity for a strip footing is much greater than for circular and square footings. Research works for the reasonable estimation of the bearing capacity of footings in soft rock are facilitated by this study.

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