scholarly journals Dynamic tensile properties, deformation, and failure testing of impact-loaded coal samples with various water content

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhen Wei ◽  
Ke Yang ◽  
Xiao-Lou Chi ◽  
Xiang He ◽  
Xin-Yuan Zhao ◽  
...  
Keyword(s):  
Water Content ◽  
Coal Sample ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Test System ◽  
Image Correlation ◽  
Tensile Failure ◽  
Peak Strain ◽  
Rate Correlation

AbstractDisc coal samples with different water content were tested using the split Hopkinson press bar test system. Their dynamic tensile failure process was monitored via an ultra-high-speed digital image correlation system. The deformation trend and failure characteristics as a function of the water content were analyzed, and the water content effect on dynamic mechanical properties was investigated. The results demonstrated that the dynamic stress–strain curve of the coal samples consisted of four stages. As the water content increased, the coal sample brittleness degraded, while its ductility was enhanced. Quadratic polynomial functions can describe dynamic peak stress, peak strain, and loading pressure. Under different loading pressures, the dynamic peak stress exhibited a concave bending trend as the water content increased. The coal sample's dynamic tensile strength had a strong rate correlation, and the saturated coal sample exhibited the highest rate correlation. Under high-rate loading, the inertia effect and the Stefan effect of water in coal samples hinder the initiation and propagation of coal sample cracks, improving the coal sample's strength. The research results provide a basic theoretical basis for the prevention and control of rock burst in coal mines.

Study of the Effect of Joint Trace Lengths on Failure Strength of Rock

2014 ◽  
Vol 501-504 ◽  
pp. 603-606
Author(s):  
Yun Jie Zhang ◽  
Tao Xu
Keyword(s):  
Compressive Strength ◽  
Process Analysis ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Experimental Results ◽  
Peak Strain ◽  
Joint Orientation ◽  
Trace Length ◽  
Failure Patterns

Numerical simulations the different rock sample in the uniaxial compression have been conducted using Rock Failure Process Analysis program (RFPA2D) to evaluate the effects of joint trace lengths on the overall mechanical behaviour of jointed rock masses in this paper. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding experimental results. We found that for a series of partially-spanning joint geometries with the same joint orientation, the projected area will be proportional to the square of the trace length. Thus, the relationship between compressive strength and partially-spanning joint geometry for the tests carried out to explore the influence of joint trace length may be expressed as a linear correlation between compressive strength and projected area.Numerical simulations agree well with experimental results.

Numerical Study of Effect of Joint Tip Distance from Sample End on Rock Failure

2014 ◽  
Vol 501-504 ◽  
pp. 244-247
Author(s):  
Yun Jie Zhang ◽  
Cheng Fan
Keyword(s):  
Uniaxial Compression ◽  
Numerical Study ◽  
Process Analysis ◽  
Rock Fracture ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Rock Failure ◽  
Peak Strain ◽  
Failure Patterns

In this paper,the mechanical properties of rock experiencing the variation of joint tip distance from sample end under uniaxial compression condition were simulated.Numerical simulation for the different rock sample in the uniaxial compression have been conducted to evaluate the effects of joint tip distance from sample end on the overall mechanical behaviour of jointed rock masses. It was done using the Rock Failure Process Analysis program RFPA2D. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding physical tests. We found that specimen joint tip distance from sample end corresponding value (distance from the crack tip to the compression surface) linear relationship with the compressive strength values .Numerical simulations agree well with physical results, it is shown that RFPA2D is suitable for the analysis of joint tip distance from sample end effect on rock fracture.

Numerical Simulation of the Effect of Joint Orientation on the Failure Strength of Rock

2013 ◽  
Vol 477-478 ◽  
pp. 577-581
Author(s):  
Yue Long Yan ◽  
Tao Xu ◽  
Yun Jie Zhang ◽  
P.L.P. Wasantha
Keyword(s):  
Numerical Simulations ◽  
Uniaxial Compression ◽  
Process Analysis ◽  
Rock Fracture ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Peak Strain ◽  
Joint Orientation ◽  
Failure Patterns

The mechanical properties of rock experiencing the variation of joint orientation under uniaxial compression condition were simulated in this paper. Numerical simulations on rock sample in uniaxial compression have been conducted to evaluate the effects of joint orientation on the overall mechanical behaviour of jointed rock masses. It was done using the Rock Failure Process Analysis program RFPA2D. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding physical tests. Numerical simulations agree well with physical results, it is shown that RFPA2D is suitable for the analysis of joint orientation effect on rock fracture.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

scholarly journals Dynamic Characteristics of Sandstone under Coupled Static-Dynamic Loads after Freeze-Thaw Cycles

2020 ◽  
Vol 10 (10) ◽  
pp. 3351
Author(s):  
Bo Ke ◽  
Jian Zhang ◽  
Hongwei Deng ◽  
Xiangru Yang
Keyword(s):  
Energy Absorption ◽  
Dynamic Characteristics ◽  
Shear Failure ◽  
Strain Curve ◽  
Peak Stress ◽  
Peak Strain ◽  
Compression Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Freeze Thaw

The effect of temperature fluctuation on rocks needs to be considered in many civil engineering applications. Up to date the dynamic characteristics of rock under freeze-thaw cycles are still not quite clearly understood. In this study, the dynamic mechanical properties of sandstone under pre-compression stress and freeze-thaw cycles were investigated. At the same number of freeze-thaw cycles, with increasing axial pre-compression stress, the dynamic Young’s modulus and peak stress first increase and then decrease, whereas the dynamic peak strain first decreases and then increases. At the same pre-compression stress, with increasing number of freeze-thaw cycles, the peak stress decreases while the peak strain increases, and the peak strain and peak stress show an inverse correlation before or after the pre-compression stress reaches the densification load of the static stress–strain curve. The peak stress and strain both increase under the static load near the yielding stage threshold of the static stress–strain curve. The failure mode is mainly shear failure, and with increasing axial pre-compression stress, the degree of shear failure increases, the energy absorption rate of the specimen increases first and then decreases. With increasing number of freeze-thaw cycles, the number of fragments increases and the size diminishes, and the energy absorption rates of the sandstone increase.

scholarly journals Full- and Local-Field Strain Evolution and Fracture Behavior of Precracked Granite under Coupled Static and Dynamic Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Diyuan Li ◽  
Feihong Gao ◽  
Zhenyu Han ◽  
Quanqi Zhu
Keyword(s):  
Local Field ◽  
Split Hopkinson Pressure Bar ◽  
Failure Process ◽  
Image Correlation ◽  
Field Strain ◽  
Dynamic Loads ◽  
Failure Behavior ◽  
Peak Strain ◽  
Strain Evolution ◽  
Static And Dynamic Loads

Flaws and discontinuities play a crucial role in the failure process of rocks. To investigate the fracturing mechanism of rock with combined flaws composed of crack and hole, the digital image correlation (DIC) method is used to record and analyze the rock failure behavior. Coupled static and dynamic loads are applied on granite specimens with prefabricated flaws by a modified split Hopkinson pressure bar (SHPB) device. The dynamic mechanical properties of the granite specimens are affected by the flaw inclinations with the loading directions. With the inclination angle increasing, the combined strength and peak strain both decrease first and then increase. Full- and local-field strain evolution of the granite specimens is analyzed in a quantitative way by using DIC technique. The specimens with a flaw angle of 45° are broken relatively evenly with homogenous small particle sizes. The variation trend of fragment sizes is consistent with that of combined strength and absorption energy of the specimens.

Numerical Simulation of the Effect of Temperature on the Failure Strength of Rock

2013 ◽  
Vol 690-693 ◽  
pp. 1737-1740
Author(s):  
Lin Bu ◽  
Tao Xu ◽  
Yun Jie Zhang
Keyword(s):  
Mechanical Properties ◽  
Rock Fracture ◽  
Strain Curve ◽  
Peak Stress ◽  
Effect Of Temperature ◽  
Peak Strain ◽  
Failure Strength ◽  
Stress Strain Curve ◽  
Physical Tests ◽  
Compression Condition

The mechanical properties of granite experiencing high temperatures under uniaxial compression condition were simulated in this paper. Numerically simulated stress-strain curve, peak stress, peak strain and the tangent elastic modulus were compared with the corresponding physical tests. Simulated results agree well with physical tests results, it is shown that Abaqus is suitable for the analysis of the temperature effect on rock fracture.

scholarly journals Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Huamin Li ◽  
Huigui Li ◽  
Baobin Gao ◽  
Dongjie Jiang ◽  
Junfa Feng
Keyword(s):  
Acoustic Emission ◽  
Elasticity Modulus ◽  
Loading Rate ◽  
Peak Stress ◽  
Test System ◽  
Strong Impact ◽  
Peak Strain ◽  
Compression Tests ◽  
Loading Rates ◽  
The Relationship

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

scholarly journals On the Fracture Evolution and Instability of Pyrite-Filled Marble Exposed to Freeze-Thaw-Compression Loads

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Yu Wang ◽  
Haonan Yang ◽  
Chun Zhu ◽  
Shaohua Gao
Keyword(s):  
Progressive Failure ◽  
Failure Process ◽  
Peak Stress ◽  
Image Correlation ◽  
Natural Fracture ◽  
Open Pit ◽  
Full Field ◽  
Strain Concentration ◽  
Freeze Thaw ◽  
Stimulation Of

Abstract The preexistence of the geological discontinuities in cold regions is susceptible to freeze-thaw weathering and rock instability, and even the occurrence of geological hazards is strongly impacted by the discontinuities. Knowledge of how natural fracture affects the rock field deformation is crucial to rock stability prediction. This work is aimed at revealing the influences of freeze-thaw on failure process for pyrite-filled marble obtained from an open pit slope. All the tested marbles were selected to roughly have the same initial pyrite band; the full-field displacement and the progressive failure behaviors under uniaxial compression were qualitatively and quantitatively analyzed using 3D digital image correlation (3D DIC) technique. The testing results show that the previous freeze-thaw action weakens the cementation between the rock matrix and pyrite band; the peak stress and strain are obviously impacted by the freeze-thaw treatment. In addition, the stimulation of pyrite bands influences the displacement development and high strain concentration pattern. The stimulation of pyrite band results in the formation of strain concentration zone, and shear sliding occurs until rock failure. Moreover, it is found that the stimulation of pyrite band and its localized strain takes place progressively and develops fast for marble exposed to higher freeze-thaw treatment. It is suggested that the field deformation development depends on the stimulation of the pyrite bands.

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