Assessment of Inherent Anisotropy and Confining Pressure Influences on Mechanical Behavior of Anisotropic Foliated Rocks Under Triaxial Compression

2015 ◽  
Vol 49 (6) ◽  
pp. 2155-2163 ◽  
Author(s):  
Davood Fereidooni ◽  
Gholam Reza Khanlari ◽  
Mojtaba Heidari ◽  
Ali Asghar Sepahigero ◽  
Amir Pirooz Kolahi-Azar
Keyword(s):  
Mechanical Behavior ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Inherent Anisotropy

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.

Influence of Clay Mineral Content on the Mechanical Properties and Microfabrics of Tailings

2021 ◽  
Author(s):  
Chao Zhang ◽  
Zhenkai Pan ◽  
Changkun Ma ◽  
Lei Ma ◽  
Xueting Li
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Mineral Content ◽  
Triaxial Compression ◽  
Clay Content ◽  
Nitrogen Adsorption ◽  
Confining Pressure ◽  
Compression Tests

Abstract Clay mineral content has an important influence on the mechanical behavior of tailings, and the mechanical behavior of tailings directly affects the stability of tailings dams. XRF and XRD tests were carried out on tailings from three different regions. The chemical and mineral compositions of the tailings are analyzed. The strength and failure deformation of tailings were studied by carrying out laboratory triaxial compression tests. The effect of clay content on the stress path of tailings was investigated. The microfabric of tailings samples was examined with scanning electron microscopy (SEM) and nitrogen adsorption tests. The results show that the confining pressure corresponding to the samples exhibiting strain hardening increases with increasing clay mineral content in the tailings. The cohesion of tailings increases linearly, and the specific surface area decreases as the content of clay minerals increases. Nitrogen adsorption test results reveal from a microscopic point of view that changes in pore structure are associated with the content of clay minerals. The higher the content of clay minerals is, the higher the proportion of micropores (aggregated interior). Macroscopically, the overall porosity decreases and the fineness of the pores increases with clay content, which will directly affect the mechanical properties of tailings.

Laboratory Investigation on Mechanical Behavior of Artificial Ice under Triaxial Compression

2014 ◽  
Vol 887-888 ◽  
pp. 903-906
Author(s):  
Xiang Tian Xu ◽  
Jun Hong Yuan ◽  
Rui Qiang Bai
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Laboratory Investigation ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Experimental Results ◽  
Compression Tests ◽  
Strain Behavior ◽  
Triaxial Compression Tests ◽  
Deformation And Strength Characteristics

A series of triaxial compression tests on an artificial ice with strain rate of 1.67×10-4/s at-6°C are carried out to investigate the mechanical behavior of ice. The influence of confining pressure on deformation and strength characteristics of ice is analyzed based on the experimental results. The results show that the stress-strain behavior and the strength of ice changes with increasing pressure in two distinct phases.

scholarly journals Investigation on the Anisotropy of Mechanical Properties and Brittleness Characteristics of Deep Laminated Sandstones

2021 ◽  
Author(s):  
Mingyang Zhai ◽  
Zenglin Wang ◽  
Liaoyuan Zhang ◽  
Aishan Li ◽  
Zilin Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Brittleness Index ◽  
Energy Transformation ◽  
Compression Tests ◽  
Shape Variation ◽  
Inherent Anisotropy ◽  
Rock Brittleness ◽  
Anisotropy Of Mechanical Properties

Abstract Rock brittleness is a crucial mechanical property and essential for fracability evaluation and fracturing scheme design in unconventional reservoirs. However, the influence of inherent anisotropy on deep laminated sandstone’s mechanical properties and brittleness characteristics is rarely investigated. The energy transformation and damage evolution reflected by complete stress-strain curves are analyzed during the entire process of rock rupture under compressions. A new brittleness index is established based on energy evolution during sandstone failure. Its advantages involve comprehensively considering the energy transformation characteristics at both pre-peak and post-peak stages and the capability to characterize the effect of confining pressure and bedding plane (BP) geometry on sandstone brittleness. The triaxial compression tests on sandstones are conducted to validate the reliability and accuracy of the new brittleness index. Numerical simulations are then performed to further investigate the manner in which BP angle, BP density, and confining pressure control the brittleness anisotropy of deep laminated sandstones based on the finite element method. Then the acoustic emission (AE) characteristics of anisotropic sandstone and correlations between AE mode and brittleness index are discussed. The results indicated that the anisotropy of mechanical properties and brittleness of deep laminated sandstones were significantly affected by BP angle, BP density, and confining pressure. With the increase of BP angle, the brittleness index of deep laminated sandstone decreases first and then increases, showing a U-shape variation law, whose maximum and minimum values are obtained at φ =0° and φ =45°, respectively. The AE characteristics were closely related to rock brittleness, which was jointly controlled by BP geometry and confining pressure. The results provide a basis for the brittleness and fracability evaluation and optimum hydraulic fracturing design in deep laminated sandstones.

scholarly journals Mechanical Behavior of Coupled Elastoplastic Damage of Clastic Sandstone of Different Burial Depths

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1640
Author(s):  
Yu Zhang ◽  
Lu Wang ◽  
Goangseup Zi ◽  
Yan Zhang
Keyword(s):  
Plastic Deformation ◽  
Mechanical Behavior ◽  
Oil And Gas ◽  
Triaxial Compression ◽  
Mechanical Damage ◽  
Confining Pressure ◽  
Internal Variables ◽  
Burial Depth ◽  
Compression Tests ◽  
Elastoplastic Damage

Clastic sandstone is widely distributed in oil and gas reservoirs; its internal structure has many micro-defects. Under different stress environments of burial depth, significant damage evolution and plastic deformation easily occur. A series of triaxial compression tests were performed to study the coupled elastoplastic damage mechanical behavior of clastic sandstone samples at different burial depths ranging from 581.28 m to 979.82 m. Results reveal that the stress-strain responses of clastic sandstone samples exhibit significant nonlinear and softening characteristics. The mechanical behavior is due to the coupling of plastic deformation and mechanical damage. Plastic and damage internal variables cause damage stiffness degradation and plastic flow. Considering the coupling of elastoplastic damage in the loading process, an elastoplastic damage coupling model is proposed to study the mechanical behavior of different burial depth clastic sandstones. The model can effectively describe the mechanical behavior of clastic sandstone, such as the volume compression and dilatancy transformation, plastic hardening and damage softening, which are in good agreement with the experimental results. Furthermore, the mechanical behavior of the clastic sandstone shows a dependency on the confining pressure and burial depth. The load-bearing capacity and the ability to resist deformation of the clastic sandstone are improved as the confining pressure and burial depth increase. Relevant results can provide reliable basis for the safe exploitation of oil and gas engineering.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Mechanical behavior of human morselized cancellous bone in triaxial compression testing

1998 ◽  
Vol 16 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Michael D. Brodt ◽  
Colby C. Swan ◽  
Thomas D. Brown
Keyword(s):  
Mechanical Behavior ◽  
Cancellous Bone ◽  
Triaxial Compression ◽  
Compression Testing

Mechanical behaviour of powders using a medium pressure flexible boundary cubical triaxial tester

2003 ◽  
Vol 217 (3) ◽  
pp. 233-241 ◽  
Author(s):  
F Li ◽  
V M Puri
Keyword(s):  
Shear Modulus ◽  
Mechanical Behaviour ◽  
Triaxial Compression ◽  
Three Dimensional ◽  
Volumetric Strain ◽  
Confining Pressure ◽  
Alumina Powder ◽  
Medium Pressure ◽  
Mean Pressure ◽  
Confining Pressures

A medium pressure (<21 MPa) flexible boundary cubical triaxial tester was designed to measure the true three-dimensional response of powders. In this study, compression behaviour and strength of a microcrystalline cellulose powder (Avicel® PH102), a spray-dried alumina powder (A16SG), and a fluid-bed-granulated silicon nitride based powder (KY3500) were measured. To characterize the mechanical behaviour, three types of triaxial stress paths, that is, the hydrostatic triaxial compression (HTC), the conventional triaxial compression (CTC), and the constant mean pressure triaxial compression (CMPTC) tests were performed. The HTC test measured the volumetric response of the test powders under isostatic pressure from 0 to 13.79MPa, during which the three powders underwent a maximum volumetric strain of 40.8 per cent for Avicel® PH102, 30.5 per cent for A16SG, and 33.0 per cent for KY3500. The bulk modulus values increased 6.4-fold from 57 to 367MPa for Avicel® PH102, 3.7-fold from 174 to 637 MPa for A16SG, and 8.1-fold from 74 to 597MPa for KY3500, when the isotropic stress increased from 0.69 to 13.79 MPa. The CTC and CMPTC tests measured the shear response of the three powders. From 0.035 to 3.45MPa confining pressure, the shear modulus increased 28.7-fold from 1.6 to 45.9MPa for Avicel® PH102, 35-fold from 1.7 to 60.5MPa for A16SG, and 28.5-fold from 1.5 to 42.8MPa for KY3500. In addition, the failure stresses of the three powders increased from 0.129 to 4.41 MPa for Avicel® PH102, 0.082 to 3.62 MPa for A16SG, and 0.090 to 4.66MPa for KY3500, respectively, when consolidation pressure increased from 0.035 to 3.45MPa. In addition, the shear modulus and failure stress values determined from the CTC test at 2.07, 2.76, and 3.45MPa confining pressures are consistently greater than those from the CMPTC test at the same constant mean pressures. This observation demonstrates the influence of stress paths on material properties. The CTT is a useful tool for characterizing the three-dimensional response of powders and powder mixtures.

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