scholarly journals The Effect of Bedding Structure on Mechanical Property of Coal

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Zetian Zhang ◽  
Ru Zhang ◽  
Guo Li ◽  
Hegui Li ◽  
Jianfeng Liu
Keyword(s):  
Mechanical Property ◽  
Uniaxial Compression ◽  
Peak Stress ◽  
Natural Fracture ◽  
Test Results ◽  
Compression Tests ◽  
Average Amount ◽  
Uniaxial Compression Strength ◽  
Bedding Planes ◽  
Close Relationship

The mechanical property of coal, influencing mining activity considerably, is significantly determined by the natural fracture distributed within coal mass. In order to study the effecting mechanism of bedding structure on mechanical property of coal, a series of uniaxial compression tests and mesoscopic tests have been conducted. The experimental results show that the distribution characteristic of calcite particles, which significantly influences the growth of cracks and the macroscopic mechanical properties of coal, is obviously affected by the bedding structure. Specifically, the uniaxial compression strength of coal sample is mainly controlled by bedding structure, and the average peak stress of specimens with axes perpendicular to the bedding planes is 20.00 MPa, which is 2.88 times the average amount of parallel ones. The test results also show a close relationship between the bedding structure and the whole deformation process under uniaxial loading.

Two-Parameter Parabolic Mohr Strength Criterion and Its Damage Regularity

2006 ◽  
Vol 306-308 ◽  
pp. 327-332 ◽  
Author(s):  
Chun Guang Li ◽  
Xiu Run Ge ◽  
Hong Zheng ◽  
Shui Lin Wang
Keyword(s):  
Uniaxial Tension ◽  
Principal Stress ◽  
Uniaxial Compression ◽  
Strength Criterion ◽  
Friction Angle ◽  
Tensile Failure ◽  
Compression Tests ◽  
Uniaxial Compression Strength ◽  
Griffith Criterion ◽  
Two Parameter

A series of formulas about two-parameter parabolic Mohr strength criterion(2-PP Mohr criterion) are derived. Based on the results of uniaxial tension and uniaxial compression tests, the parameters involved in the criterion can be easily determined, then the criterion in terms of the major principal stress and the minor principal stress is derived, and the damage pattern is also discussed. At last, the formulas about the rupture angle and the friction angle are presented, and their relationship is also given. 2-PP Mohr criterion can describe not only shear but also tensile failure. In this criterion the ratio of the uniaxial compression strength and the uniaxial tension strength is not confined as in Griffith criterion. The formula about the rupture angle provides steady theoretical foundation for determining the direction of crack faces and damage patterns in the computation of macro crack propagation. In fact, Griffith criterion is only a special case of the two-parameter parabolic Mohr strength criterion proposed in this present paper.

scholarly journals Experimental and Numerical Investigation of Failure Characteristics and Mechanism of Granites with Different Joint Angles

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhenhua Wang ◽  
Jun Fang ◽  
Gang Wang ◽  
Yifan Jiang ◽  
Dongwei Li
Keyword(s):  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Elastic Strain Energy ◽  
Peak Stress ◽  
Peak Strength ◽  
Particle Flow Code ◽  
Dissipated Energy ◽  
Shear Cracks ◽  
Compression Tests ◽  
Dip Angle

The uniaxial compression tests were conducted on granite samples with different joint dip angles to more favorably explore the influences of the nonconsecutive joint on mechanical properties and deformation characteristics of the rock mass. The stress-strain curves, deformation and strength characteristics, and energy evolution process of the samples were analyzed. Numerical simulation using particle flow code (PFC) is employed to study the crack propagation process. The mode of jointed and fractured rock was investigated. The research results showed a significant reduction in both the peak strength and elastic modulus of jointed samples compared with intact ones: the peak strength and elastic modulus drop to the minimum at the joint dip angle of about 45°, especially for the peak strength, which takes up about 55% of the intact samples. The fractured samples’ total energy, elastic strain energy, and dissipated energy during the uniaxial compression drop significantly relative to intact samples. The proportion of the fracture modes varies with different joint dip angles, in which the ratio of shear cracks grows at first and then declines, with the highest balance at the dip angle of 45°. The damage stress’s sensitivity to the dip angle change is greater than that of the peak stress, with reduction amplitude more extensive than the latter.

Strength Attenuation Law of Damaged Rock Samples and its Structure Effect

2013 ◽  
Vol 353-356 ◽  
pp. 602-607
Author(s):  
Hai Jian Su ◽  
Hong Wen Jing ◽  
Chen Wang ◽  
Bo Meng
Keyword(s):  
Uniaxial Compression ◽  
Axial Compression ◽  
Confining Pressure ◽  
Structure Effect ◽  
Thick Wall ◽  
Test Results ◽  
Compression Tests ◽  
Rock Samples ◽  
Nonlinear Fitting ◽  
Attenuation Value

In order to study the post-peak mechanics behavior of rock samples with a thick wall cylinder structure, damaged rock samples were precast with a new method. The uniaxial compression tests and tri-axial compression tests were conducted on the samples and the test results were compared with that of complete rock samples. The results show that strength attenuation value of the damaged samples increased with the confining pressure and the specific relationship was obtained by nonlinear fitting as (is the strength attenuation value and is the confining pressure); destructiveness of damaged samples was more serious than the complete ones; a new nearly horizontal failure phenomenon appeared under the tri-axial compression and it was more general with the increase of confining pressure. Structure effect of uniaxial strength attenuation was revealed based on the particle flow software system (PFC) and the corresponding theoretical model was found as (is the strength attenuation value under uniaxial compression of any damaged sample with a thick wall cylinder structure; is the strength attenuation value of standard damaged samples under uniaxial compression; is the structure ratio, and are the parameters of the material). Characteristic value of the strength attenuation value under uniaxial compression was obtained by calculation when the structure ratio was indefinitely large.

scholarly journals A Stress-Strain Model for Brick Prism under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Yong-Ha Hwang
Keyword(s):  
Strain Curve ◽  
Peak Stress ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Proposed Model ◽  
Relationship Model ◽  
Strain Relationship ◽  
Strain Model

This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.

scholarly journals Experimental Study on the Calibration of Microparameters of Dolomite in the Barun Open-Pit Mine on the Basis of the Parallel Bond Model

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhiheng Dang ◽  
Zuoming Yin ◽  
Desheng Wang ◽  
Mingyu Fu ◽  
Qi Yin
Keyword(s):  
Mechanical Properties ◽  
Numerical Simulation ◽  
Uniaxial Compression ◽  
Open Pit Mine ◽  
Particle Flow ◽  
Open Pit ◽  
Test Results ◽  
Compression Tests ◽  
Simulation Test ◽  
Bond Model

The microparameter calibration of the particle flow parallel bond model (PBM) is mostly based on a uniaxial compression test. The microparameters calibrated only by uniaxial compression tests cannot be directly used to study the mechanical properties of rocks with surrounding pressure conditions. To analyze the relationship between the macroparameters and microparameters in the model and select appropriate particle flow model parameters, this study conducted a particle flow numerical simulation experiment based on the basic test principles of the uniaxial compression, Brazilian splitting, and triaxial compression tests. An orthogonal experimental design was performed for the calibration of the microparameters of the particle flow PBM, and multifactor analysis of variance was used to screen out the factors that have a considerable influence on the experimental indicators. Regression analysis was performed on the significant influencing factors and test indicators, and the corresponding linear and nonlinear relationships between the macroparameters and microparameters were obtained. Lastly, the microparameters of the model were determined in accordance with the macroparameters of the mechanical test of the Barun open-pit mine dolomite, and a numerical simulation test was conducted. Simulation test results were consistent with the actual test results, thus providing a basis for a subsequent numerical simulation study on the mechanical properties of dolomite.

scholarly journals Effect of Thermal Environment on the Mechanical Behaviors of Building Marble

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Haijian Su ◽  
Hongwen Jing ◽  
Qian Yin ◽  
Liyuan Yu
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Building Materials ◽  
Elasticity Modulus ◽  
Thermal Environment ◽  
Peak Stress ◽  
Compression Tests ◽  
Mechanical Behaviors ◽  
Thermal Environments ◽  
Concrete Building

High temperature and thermal environment can influence the mechanical properties of building materials worked in the civil engineering, for example, concrete, building rock, and steel. This paper examines standard cylindrical building marble specimens (Φ50 × 100 mm) that were treated with high temperatures in two different thermal environments: vacuum (VE) and airiness (AE). Uniaxial compression tests were also carried out on those specimens after heat treatment to study the effect that the thermal environment has on mechanical behaviors. With an increase in temperature, the mechanical behavior of marble in this study indicates a critical temperature of 600°C. Both the peak stress and elasticity modulus were larger for the VE than they were for the AE. The thermal environment has an obvious influence on the mechanical properties, especially at temperatures of 450∼750°C. The failure mode of marble specimens under uniaxial compression is mainly affected by the thermal environment at 600°C.

EXPERIMENTAL AND THEORETICAL STUDY ON FREEZE-THAWING DAMAGE PROPAGATION OF SATURATED ROCKS

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1853-1858 ◽  
Author(s):  
QUANSHENG LIU ◽  
GUANGMIAO XU ◽  
XIAOYAN LIU
Keyword(s):  
Uniaxial Compression ◽  
Influence Factors ◽  
Compression Tests ◽  
Freezing And Thawing ◽  
Uniaxial Compression Strength ◽  
Red Sandstone ◽  
Damage Propagation ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Damage Process

The freezing and thawing cycles tests were conducted on red sandstone and shale. In this paper, freezing-thawing damage propagation processes are analyzed, and two deterioration modes, i.e. scaling mode for red sandstone and fracturing mode for shale, are suggested. The uniaxial compression tests are also conducted on the two types of rock subjected to different freeze-thaw cycles at room temperature. It is shown that the uniaxial compression strength and the elastic modulus of rocks at low-temperature depended on the number of freeze-thaw cycles. The mechanism and influence factors of rock deterioration due to freeze-thaw are analyzed, and the damage process of rock should be divided into two coupled parts: rocks damage due to freeze-thaw cycle as well as the damage propagation caused by stress erosion. The damage evolvement equations for the two rocks are established, and the constitutive equations for the two types of rock subjected to freeze-thaw are deduced, accordingly. It is approved that the constitutive model considering the freeze-thaw damage is credible and can be used for the following theory analysis.

Implementation of Twin Reorientation and Softening Schemes in a Polycrystal Plasticity Model for Mg Alloys

2007 ◽  
Vol 558-559 ◽  
pp. 1063-1068
Author(s):  
Shi Hoon Choi ◽  
Y.S. Song ◽  
Jong Kweon Kim ◽  
B.J. Jung ◽  
Yong Bum Park
Keyword(s):  
Uniaxial Compression ◽  
Work Hardening ◽  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Rolling Direction ◽  
Peak Stress ◽  
Deformation Twinning ◽  
Compression Tests ◽  
Polycrystal Plasticity ◽  
Hot Rolled

Uniaxial compression tests on hot-rolled AZ31 Mg alloy were carried out at a temperature of 300°C. In order to investigate work hardening and texture evolution during plastic deformation, cylindrical specimens were compressed to the rolling direction. Experimental investigation reveals that flow curves are strongly dependent on microstructure evolution such as deformation twinning and softening phenomenon. The occurrence of deformation twinning and softening phenomenon was revealed by the observation of microtexture using electron backscatter diffraction (EBSD). A visco-plastic self-consistent (VPSC) polycrystal model was used to simulate the work hardening, softening and texture evolution during the uniaxial compression. In order to calculate orientation of deformation twins, predominant twin reorientation (PTR) scheme was implemented into the polycrystal model. A softening scheme was also implemented in the polycrystal model to predict softening phenomenon and texture evolution after a peak stress.

scholarly journals Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Huigui Li ◽  
Zhengkai Yang ◽  
Huamin Li
Keyword(s):  
Elastic Modulus ◽  
Failure Mechanism ◽  
Uniaxial Compression ◽  
Compression Strength ◽  
Damage Model ◽  
Strain Curve ◽  
Compression Tests ◽  
Uniaxial Compression Strength ◽  
Stress Strain ◽  
Joint Thickness

The mechanics of rock mass is significantly affected by joints, but many existing studies of jointed rocks make simplifications that do not consider the joint thickness. To further study the influence of joint thickness on rock mechanics (mechanical properties, failure mechanism, damage model, etc.), we fabricated jointed siltstone specimens with different joint thickness (5, 10, 15, and 20 mm) and the specimens were subjected to uniaxial compression tests. The effects of joint thickness on the uniaxial compression strength (UCS), the strain at UCS, the elastic modulus, and the stress-strain curves were thus analyzed. For the stress-strain curve, with rising joint thickness, the upper concave in the initial compression stage intensified, the slope of the stress-strain in the elastic stage decreased, and the sudden stress drop after peak strength became more obvious. Both the peak compression strength and the elastic modulus gradually decreased with rising joint thickness, but a positive correlation was found between the strain at UCS and the joint thickness.

Mechanical properties and damage constitutive model for uniaxial compression of salt rock at different loading rates

2021 ◽  
pp. 105678952098386
Author(s):  
Junbao Wang ◽  
Qiang Zhang ◽  
Zhanping Song ◽  
Yuwei Zhang ◽  
Xinrong Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Loading Rate ◽  
Peak Stress ◽  
Test Results ◽  
Salt Rock ◽  
Loading Rates ◽  
Damage Constitutive Model ◽  
Rock Specimens

To study the effect of loading rate on the mechanical properties of salt rock, uniaxial compression tests and acoustic emission tests at different loading rates were carried out on salt rock specimens. The test results show that with increases in loading rate, the peak stress of salt rock increases first and then essentially remains unchanged, and the elastic modulus increases gradually, while the strain at peak stress decreases gradually. Moreover, the Poisson’s ratio is independent of loading rate. The macroscopic failure modes of the salt rock specimens at different loading rates are all ‘X’-type conjugate shear failure. However, the loading rate is closely related to the degree of fracture, such that the smaller the loading rate is, the higher is the degree of fracture of salt rock. In order to describe the stress–strain behaviour in the process of salt rock failure, a damage variable expression represented by the deformation modulus was proposed, and a rock damage constitutive model was established according to the theory of continuum damage mechanics. The rationality of the damage constitutive model was verified by using the present uniaxial compression test results of salt rock and existing test data from the literature. The results show that the model can accurately describe the stress–strain response of rock in the failure process.

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