scholarly journals Elastoplastic Model and Three-Dimensional Method for Unsaturated Soils

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Jinjin Fang ◽  
Yixin Feng
Keyword(s):  
Constitutive Model ◽  
Unsaturated Soils ◽  
Three Dimensional ◽  
Three Dimensions ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Model Parameters ◽  
Elastoplastic Model ◽  
True Triaxial ◽  
Elastoplastic Constitutive Model

This paper proposed a new elastoplastic constitutive model to predict the deformation and strength behaviour of unsaturated soils. Applying the modified Cambridge model as a generalization, the degree of saturation is introduced into the elastoplastic model of unsaturated soil. Under the condition of ensuring that the model parameters are unchanged, the model is transformed into three dimensions based on the SMP criterion transformation stress method. Enhanced modified van Genuchten model under true triaxial conditions is also proposed in this paper to describe hydromechanical behaviours of unsaturated soils. The proposed constitutive model can capture the observed mechanical and hydraulic behaviours. Then, the model is validated via equal p and equal b value true triaxial tests, and the results show that a reasonable agreement can be obtained.

scholarly journals Dynamic triaxial constitutive model for rock subjected to initial stress

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 149-163
Author(s):  
Junzhe Li ◽  
Guang Zhang ◽  
Mingze Liu ◽  
Shaohua Hu ◽  
Xinlong Zhou
Keyword(s):  
Constitutive Model ◽  
Impact Load ◽  
Three Dimensional ◽  
Estimation Method ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Initial Pressure ◽  
Expansion Method ◽  
Three Dimensions ◽  
Model Parameters

AbstractBuilding on the existing model, an improved constitutive model for rock is proposed and extended in three dimensions. The model can avoid the defect of non-zero dynamic stress at the beginning of impact loading, and the number of parameters is in a suitable range. The three-dimensional expansion method of the component combination model is similar to that of the Hooke spring, which is easy to operate and understand. For the determination of model parameters, the shared parameter estimation method based on the Levenberg–Marquardt and the Universal Global Optimization algorithm is used, which can be well applied to models with parameters that do not change with confinement and strain rates. According to the established dynamic constitutive equation, the stress–strain curve of rock under the coupling action of the initial hydrostatic pressure load and constant strain-rate impact load can be estimated theoretically. By comparing the theoretical curve with the test data, it is shown that the dynamic constitutive model is suitable for the rock under the initial pressure and impact load.

Anisotropic Behavior of Geomaterial under Three-Dimensional Stress States

2010 ◽  
Vol 160-162 ◽  
pp. 1425-1431
Author(s):  
Kun Yong Zhang ◽  
Yan Gang Zhang ◽  
Chi Wang
Keyword(s):  
Stress State ◽  
Principal Stress ◽  
Three Dimensional ◽  
Complex Stress State ◽  
Triaxial Tests ◽  
Induced Anisotropy ◽  
Principal Stresses ◽  
True Triaxial ◽  
Stress Effects ◽  
Stress Induced Anisotropy

Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.

Experimental and Numerical Characterization of the Stress-Strain Behavior of Weak Sandstone Formations for Sanding Assessment

2018 ◽  
Author(s):  
Nubia Aurora González Molano ◽  
Jacobo Canal Vila ◽  
Héctor González Pérez ◽  
José Alvarellos Iglesias ◽  
M. R. Lakshmikantha
Keyword(s):  
Constitutive Model ◽  
Equivalent Plastic Strain ◽  
Experimental Tests ◽  
Thick Wall ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Model Parameters ◽  
Sand Production ◽  
Strain Behavior ◽  
Weak Sandstone

In this study an extensive experimental program has been carried out in order to characterize the mechanical behavior of two weak sandstone formations of an offshore field for application to sand production modeling. The experimental tests included Scratch tests, Triaxial tests and Advanced thick wall cylinder tests (ATWC) where the sand production initiation and the cumulative sand produced were registered. Numerical simulations of experimental tests were then performed using an advanced elasto-plastic constitutive model. Triaxial tests simulations allowed calibrating the constitutive model parameters. These parameters were employed for the numerical simulation of the ATWC in order to determine the equivalent plastic strain threshold required to the onset of sand production observed in laboratory for sanding assessment. Results obtained highlight the importance to use a realistic representation of the rock behavior focusing on post-yield behavior in order to build confidence in model predictions.

scholarly journals An Elastoplastic Model for Unsaturated Soils Under General Three-Dimensional Conditions

2006 ◽  
Vol 46 (5) ◽  
pp. 613-628 ◽  
Author(s):  
M.M. Farias ◽  
M. Pinheiro ◽  
M.P. Cordao Neto
Keyword(s):  
Unsaturated Soils ◽  
Three Dimensional ◽  
Elastoplastic Model

AN ELASTOPLASTIC CONSTITUTIVE MODEL FOR POROUS MATERIALS

2013 ◽  
Vol 05 (03) ◽  
pp. 1350035 ◽  
Author(s):  
ZHUPING HUANG ◽  
YONGQIANG CHEN ◽  
SHU-LIN BAI
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Porous Materials ◽  
Constitutive Relations ◽  
Matrix Material ◽  
Three Dimensional ◽  
Porous Solids ◽  
Additional Material ◽  
Prediction Of Mechanical Properties ◽  
Elastoplastic Constitutive Model

A micromechanics-based elastoplastic constitutive model for porous materials is proposed. With an assumption of modified three-dimensional Ramberg–Osgood equation for the compressible matrix material, the variational principle based on a linear comparison composite is applied to study the effective mechanical properties of the porous materials. Analytical expressions of elastoplastic constitutive relations are derived by means of micromechanics principles and homogenization procedures. It is demonstrated that the derived expressions do not involve any additional material constants to be fitted with experimental data. The model can be useful in the prediction of mechanical properties of elastoplastic porous solids.

The Studies of Rock Damage Softening Statistical Constitutive Model under True Triaxial Stress State

2014 ◽  
Vol 580-583 ◽  
pp. 312-315
Author(s):  
Hui Mei Zhang ◽  
Xiang Miao Xie ◽  
Geng She Yang
Keyword(s):  
Constitutive Model ◽  
Strain Curve ◽  
Stress Path ◽  
Complex Stress ◽  
Model Parameters ◽  
Stress Strain ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Complex Stress Path ◽  
The Impact

From the feature of rock micro-unit failure obeys Poisson random distribution, the damage softening statistical constitutive of was established under true triaxial confinement based on D-P criterion, so the impact of the intermediate principal stress on rock deformation and failure was considered in theory, and the actual engineering rock complex stress path evolution was reflected more realistically. Furthermore, according to the geometrical conditions of stress-strain relationship, the theoretical relationship between constitutive model parameters and the stress-strain curve characteristic parameters during the process of rock softening and deforming, which enhance the adaptability of the model. Finally, the rationality of the model verified by the measured data.

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