scholarly journals Modelling the Triaxial Compression Behavior of Loess Using the Disturbed State Concept

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yali Xu ◽  
Panpan Guo ◽  
Yixian Wang ◽  
Cheng-Wei Zhu ◽  
Kang Cheng ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
Loess Soil ◽  
Confining Pressure ◽  
Structural Effect ◽  
Structural Behavior ◽  
Disturbing Function ◽  
Engineering Practice ◽  
Model Based ◽  
Disturbed State Concept

This paper investigates the triaxial compression behaviour of Q3 loess soil and the construction of a constitutive model accounting for the structural effect of loess on the basis of the disturbed state concept. By analyzing the triaxial compression testing results, we have established a new disturbing function with respect to the volumetric and shear moduli parameters. A research into the evolution laws of the disturbing function was also conducted, followed by the construction of a constitutive model for loess soil as well as the verification of the constitutive model with model test results. The results indicate that the double-parameter disturbing function evolves in an exponential form, capturing well the effect of moisture content and confining pressure on the loess structural behavior. The parameters of the constructed constitutive model based on the disturbed state are easy to be obtained and have clarified physical meanings. Considering the effectiveness in capturing the structural behavior of the loess, the constructed constitutive model has a great potential to be applied in the engineering practice in the loess area. The constructed constitutive model based on the disturbed state concept provides new ideas for the study of the structural constitutive model of loess, which is theoretically significant.

scholarly journals Triaxial Compressive Failure Characteristics and Constitutive Model Study of Jurassic-Cretaceous Weakly Cemented Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Jinlong Cai ◽  
Wei Zou
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Ductile Failure ◽  
Mathematical Expression ◽  
Confining Pressure ◽  
Mining Area ◽  
Peak Strength ◽  
Correction Coefficient

A conventional triaxial compression test of Jurassic-Cretaceous typical weakly consolidated sandstone from a mining area in Ordos, China, was conducted using an MTS816 tester. Results showed that, before the peak, the rock had a distinct yield stage. When the specimen reached its peak strength, the strength decreased rapidly and showed an obvious brittle failure. When the confining pressure was increased to 15 MPa, the decrease of strength was slow and the rock tended toward ductile failure. With the increase of confining pressure, the cyclic strain initially increased slightly, whereas the volumetric strain increased greatly and the rock sample was in a compression state. When the load reached a critical value, the curve was reversely bent, resulting in volume expansion, whereas the peak strength, residual strength, and elastic modulus increased with confining pressure, and Poisson’s ratio decreased with the confining pressure. In the model based on macroscopic failure rock, the expression of the relationship between fracture angle and confining pressure provided a solid theoretical basis for the direction and failure mode of the macroscopic crack. Based on the rock strength theory and Weibull random distribution assumption of rock element strength, the damage variable correction coefficient was introduced when the residual strength was considered. Then, the mathematical expression of the 3D damage statistical constitutive model was established. Finally, the theoretical curve of the established constitutive model was compared with the triaxial test curve, which showed a high degree of coincidence.

scholarly journals Destructuration of saturated natural loess: From experiments to constitutive modeling

2020 ◽  
pp. 105678952093930
Author(s):  
Yukai Fu ◽  
Zhiwei Gao ◽  
Yi Hong ◽  
Tonglu Li ◽  
Akhil Garg
Keyword(s):  
Constitutive Model ◽  
Constitutive Modeling ◽  
Soil Structure ◽  
Triaxial Compression ◽  
Structural Effect ◽  
Triaxial Tests ◽  
Natural Soil ◽  
Special Focus ◽  
Compression Tests ◽  
Natural Loess

It has been well recognized that unsaturated natural loess shows significant volume contraction upon wetting due to its metastable internal structure. But the structural effect on stress–strain relationship of saturated natural (undisturbed) loess is much less explored. Few attempts have been made in proposing a constitutive model for saturated natural loess. This study presents both laboratory tests and constitutive modeling of a saturated natural loess, with special focus on the structural effect and evolution of structure damage during loading. Oedometer and drained triaxial compression tests have been carried out on undisturbed and remolded saturated loess samples. It is found that the natural soil structure has dramatic influence on mechanical behavior of loess, including the compressibility, dilatancy, and shear strength. Destructuration, which is the damage of soil structure with deformation, is observed in both oedometer and triaxial tests. A constitutive model is proposed for saturated loess based on the experimental observations. The model is established within the theoretical framework of subloading and superloading surface concepts. Destructuration of loess is assumed to be affected by both plastic volumetric and shear strain. A new method for determining the initial degree of structure is proposed. The model can reasonably predict the compression and shear behavior of both undisturbed and remolded saturated loess.

scholarly journals Disturbance Evolution Behavior of Loess Soil under Triaxial Compression

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Yali Xu ◽  
Panpan Guo
Keyword(s):  
Triaxial Compression ◽  
Deformation Modulus ◽  
Loess Soil ◽  
Confining Pressure ◽  
Compression Tests ◽  
Structural Effects ◽  
Moisture Contents ◽  
Confining Pressures ◽  
Evolution Behavior ◽  
Disturbance Function

This paper presents an investigation into the evolution law of the structural effects of Xi’an loess soil, based on the disturbed state concept. First, a series of consolidated and drained triaxial compression tests were performed on undisturbed and remoulded loess samples prepared at five different moisture contents and tested at four different confining pressures. Second, two disturbance functions with different parameters were proposed to quantify mathematically the structural effects of loess. Finally, the proposed disturbance functions were validated against documented test results by other researchers. The results indicated that the single-parameter disturbance function, with the deformation modulus as its parameter, provides convenience for application but takes no account of the respective contributions of deviatoric stress and mean stress to the disturbance evolution behavior of loess. The double-parameter disturbance function, with the shear and bulk moduli as its parameters, is capable of distinguishing these respective contributions and reflects well the disturbance evolution behavior of loess under various moisture contents and confining pressures. The effects of moisture content and confining pressure on the parameters of the disturbance functions were found to be unsteady. The proposed disturbance functions lay the foundation for establishing a constitutive model for loess accounting for the structural effect.

Laboratory Testing and Consitiutive Modeling of Coal Including Anisotropy

1992 ◽  
Vol 296 ◽  
Author(s):  
Dar-Hao Chen ◽  
Musharraf M. Zaman ◽  
Anant R. Kukreti
Keyword(s):  
Constitutive Model ◽  
Triaxial Compression ◽  
High Capacity ◽  
Ground Surface ◽  
Transversely Isotropic ◽  
Confining Pressure ◽  
Inherent Anisotropy ◽  
Deformation Response ◽  
Young’S Moduli ◽  
Confining Pressures

AbstractIn this study, the stress-deformation response of coal in the laboratory under threedimensional (3-D) loading conditions similar to those existing in an actual coal mine is investigated, and a constitutive model, including the effects of anisotropy, is developed. The coal samples were obtained from a mine in LeFlore County, Oklahoma, at a depth of approximately 25–30 ft below the ground surface. A High Capacity Cubical Device with servo-controlled independent loading along three axes of a cubical specimen and a computerized data acquisition and monitoring system were used to conduct the tests. A total of 21 tests under 4 different confining pressures and 5 different stress paths were conducted. The influence of the degree of anisotropy was investigated by comparing the transversely isotropic and isotropic idealizations for different stress paths (Triaxial Compression, Triaxial Extension and Simple Shear) at different confining pressures (1,600, 3,200 and 5,600 psi). The experimental results demonstrated that the coal exhibits inherent anisotropy and that it can be treated approximately as a transversely isotropic material. Also, the Young's moduli were found to be dependent on the confining pressure. The experimental data were used to evaluate the material constants associated with the elasto-plastic constitutive model developed in the study.

scholarly journals Study on Damage Statistical Constitutive Model of Triaxial Compression of Acid-Etched Rock under Coupling Effect of Temperature and Confining Pressure

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7414
Author(s):  
Youliang Chen ◽  
Peng Xiao ◽  
Xi Du ◽  
Suran Wang ◽  
Zhoulin Wang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Coupling Effect ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Effect Of Temperature ◽  
Acid Etching ◽  
Model Parameters ◽  
Stress Strain Curve ◽  
Stress Strain

Based on Lemaitre’s strain equivalence hypothesis theory, it is assumed that the strength of acid-etching rock microelements under the coupling effect of temperature and confining pressure follows the Weibull distribution. Under the hypothesis that micro-element damage meets the D-P criterion and based on continuum damage mechanics and statistical theory, chemical damage variables, thermal damage variables and mechanical damage variables were introduced in the construction of damage evolution equations and constitutive models for acid-etching rocks considering the coupled effects of temperature and confining pressure. The required model parameters were obtained by theoretical derivation, and the model was verified based on the triaxial compression test data of granite. Comparing the experimental stress-strain curve with the theoretical stress-strain curve, the results show that they were in good agreement. By selecting reasonable model parameters, the damage statistical constitutive model can accurately reflect the stress-strain curve characteristics of rock in the process of triaxial compression. The comparison between the experimental and theoretical results also verifies the reasonableness and reliability of the model. This model provides a new rock damage statistical constitutive equation for the study of rock mechanics and its application in engineering, and has certain reference significance for rock underground engineering.

scholarly journals Mechanical properties and constitutive analyses of basalt fiber crumb rubber mortars in soft rock roadways

2021 ◽  
Vol 303 ◽  
pp. 01023
Author(s):  
Qiao Wei-Guo ◽  
Vladimir Pershin ◽  
Qin Jun-Ling ◽  
Zhang Shuai
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Compressive Stress ◽  
Triaxial Compression ◽  
Basalt Fiber ◽  
Soft Rock ◽  
Confining Pressure ◽  
Crumb Rubber ◽  
Roadway Support ◽  
Uniaxial Compressive Stress

Uniaxial compressive stress-strain curves of several groups of basalt fiber crumb rubber mortars (BF-CRM) with different contents are tested. By comparing with the GZH model, the improved values of the parameters of the BF-CRM constitutive model based on the GZH model are obtained. Then, taking the supporting scheme of main substation of the mine as the background, using FLAC3D to simulate the roadway support, using BF-CRM to replace the ordinary mortars in the original support, and combining with the triaxial compression test of different confining pressure, the application effect of BF-CRM in roadways support is studied and analyzed.

scholarly journals Calculation of Tangent Modulus of Soils under Different Stress Paths

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Hua Huang ◽  
Min Huang ◽  
Jiangshu Ding
Keyword(s):  
Triaxial Compression ◽  
Confining Pressure ◽  
Tangent Modulus ◽  
Engineering Practice ◽  
Silty Clay ◽  
Stress Strain ◽  
Foundation Pit ◽  
Calculation Results ◽  
Chang Model ◽  
Initial Tangent Modulus

During excavation of foundation pit, soils of different sites may undergo different unloading paths. This study focuses on the tangent modulus of soil under different stress paths and provides theoretical basis for the deformation calculation of soil. In this paper, conventional triaxial compression test and K0 consolidation unloading test were conducted with mucky soil and silty clay to obtain the deformation characteristics of soils under different stress paths. Experiment results show that the soil samples exhibit distinct stress-strain characteristics under different stress paths, but they all show nonlinearity. The initial tangent modulus increases as the consolidation confining pressure intensifies. Then, based on the test data, the power function relationship between initial tangent modulus and confining pressure under unloading was verified. Simultaneously, a hyperbola function to express stress-strain relation of soils under the K0 consolidation unloading condition was proposed and proved. Finally, the formulas of the tangent modulus under K0 consolidation unloading were established referring to the derivation of that in Duncan–Chang model. The theoretical calculation results agree well with the test results. It can expand the use of the Duncan–Chang model and improve its application to engineering practice.

scholarly journals Failure Behavior and Constitutive Model of Weakly Consolidated Soft Rock

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Wei-ming Wang ◽  
Zeng-hui Zhao ◽  
Yong-ji Wang ◽  
Xin Gao
Keyword(s):  
Constitutive Model ◽  
Failure Mechanism ◽  
Triaxial Compression ◽  
Soft Rock ◽  
Confining Pressure ◽  
Western China ◽  
Failure Behavior ◽  
Correction Coefficient ◽  
Compression Tests ◽  
Mining Areas

Mining areas in western China are mainly located in soft rock strata with poor bearing capacity. In order to make the deformation failure mechanism and strength behavior of weakly consolidated soft mudstone and coal rock hosted in Ili No. 4 mine of Xinjiang area clear, some uniaxial and triaxial compression tests were carried out according to the samples of rocks gathered in the studied area, respectively. Meanwhile, a damage constitutive model which considered the initial damage was established by introducing a damage variable and a correction coefficient. A linearization process method was introduced according to the characteristics of the fitting curve and experimental data. The results showed that samples under different moisture contents and confining pressures presented completely different failure mechanism. The given model could accurately describe the elastic and plastic yield characteristics as well as the strain softening behavior of collected samples at postpeak stage. Moreover, the model could precisely reflect the relationship between the elastic modulus and confining pressure at prepeak stage.

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