Avalanche Behaviour in Microfracturing Process of 3-D Brittle Disordered Material

2005 ◽  
Vol 297-300 ◽  
pp. 2567-2572 ◽  
Author(s):  
De Shen Zhao ◽  
Tao Xu ◽  
Chun An Tang ◽  
Hou Quan Zhang ◽  
Zheng Zhao Liang
Keyword(s):  
Uniaxial Compression ◽  
Crack Nucleation ◽  
Process Analysis ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Peak Stress ◽  
Disordered Materials ◽  
Avalanche Behavior ◽  
Fracturing Process

Using a newly-developed Material Failure Process Analysis code (MFPA3D), the micro-fracturing process and the avalanche behavior characterization of brittle disordered materials such as rock or concrete is numerically studied under uniaxial compression and tension. It is found that, due to the heterogeneity of the disordered material, there is an avalanche behavior in the microcrack coalescence process. Meanwhile, a hierarchy of avalanche events also numerically observed though a study of numerically obtained acoustic emissions or seismic events. Numerical simulations indicate that macro-crack nucleation starts well before the peak stress is reached and the crack propagation and coalescence can be traced, which can be taken as a precursory to predict the macro-fracture of the brittle disordered materials. In addition, the numerically obtained results also reveal the presence of residual strength in the post-peak region and the resemblance in the stress-strain curves between uniaxial compression and tension.

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.

Analysis of Failure Mode and Propagation for Crack in Uniaxial Compression

2012 ◽  
Vol 166-169 ◽  
pp. 2929-2932
Author(s):  
Ya Zhen Sun ◽  
Xiao Xing Zhai ◽  
Jie Min Liu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Process Analysis ◽  
Failure Process ◽  
Inclined Crack ◽  
Wing Crack ◽  
Dimensionless Stress

This paper analyzed the failure mode for crack in uniaxial compression according to the stress intensity factor, and obtain that the failure mode for crack in uniaxial compression is compression-shear. The wing crack was deformed, after the crack tip initiate. By analyzing the dimensionless stress intensity factor, we obtain that the failure mode for wing crack in uniaxial compression is tension-shear, and we obtain that the dimensionless stress intensity factor for wing crack decreased with inclined angle increased. The inclined crack propagation in uniaxial compression was numerically studied using rock failure process analysis code (rfpa), and obtain that one inclined crack in uniaxial compression formed mode I offset crack parallel to load direction in the end. The numerical results of failure mode are accordance with stress intensity factor.

Numerical Studies of End Effect on Crack Propagation Behavior of Brittle Specimen Containing Pre-Existing Crack under Uniaxial Compression

2007 ◽  
Vol 353-358 ◽  
pp. 1049-1052
Author(s):  
Ming Li Huang ◽  
Shan Yong Wang ◽  
Wei Lu ◽  
Wan Cheng Zhu
Keyword(s):  
Crack Propagation ◽  
Uniaxial Compression ◽  
Process Analysis ◽  
Failure Process ◽  
End Effect ◽  
Wing Crack ◽  
Propagation Length ◽  
Propagation Behavior ◽  
Numerical Studies ◽  
Crack Propagation Process

In this paper, a Material Failure Process Analysis code (MFPA2D) was employed to investigate the interaction of end effect zone of specimen with the wing crack propagation inside the brittle specimen containing pre-existing flaws under uniaxial compression comparing with the experimental results. The numerical results show that the shorter the distance between the pre-existing flaw and the specimen's end , the slower the crack propagation process and the shorter wing propagation length is , and vice versa. In addition, the end effect zone was also influenced by the wing crack propagation.

Elasto-Plastic Cellular Automaton Simulation of Fracturing Process in Single Pre-Fractured Rocks under Uniaxial Compression

2010 ◽  
Vol 34-35 ◽  
pp. 383-386 ◽  
Author(s):  
Hua Yan Yao ◽  
Peng Zhi Pan
Keyword(s):  
Cellular Automaton ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Fractured Rock ◽  
Failure Process ◽  
Great Influence ◽  
Rock Fracturing ◽  
Rock Heterogeneity ◽  
Fracturing Process ◽  
Rock Specimens

Rock is a natural heterogeneous material and presents complicated behaviors in the fracturing process. It is prevail to study the basic failure mechanism of rocks via numerical simulation. Based on the elasto-plastic cellular automaton (EPCA) model, this paper simulates single pre-fractured rock fracturing process with consideration of rock heterogeneity on the meso-scale. In this model, the Weibull’s distribution, which characterizes heterogeneity with the homogeneous index m and the random seed parameter s, is adopted to describe the distribution of mechanical parameters of rock specimens such as cohesive strength, Young’s modulus, etc. Pre-existing crack rock specimens with different homogeneous index or the different random seed are simulated by EPCA under uniaxial compression. Numerical results show that heterogeneity has great influence on pre-fractured rock failure process, final failure modes, and the uniaxial compressive strength.

scholarly journals Numerical tests on thermal cracking characteristics of rocks with different scales

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879214 ◽  
Author(s):  
Yang Xiao ◽  
Rui Zhao ◽  
Qing-Xiang Huang ◽  
Jun Deng ◽  
Jun-Hui Lu
Keyword(s):  
Acoustic Emission ◽  
Thermal Destruction ◽  
Thermal Damage ◽  
Process Analysis ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Thermal Cracking ◽  
Tensile Failure ◽  
Failure Patterns ◽  
Different Diameters

Realistic failure process analysis, a thermal software simulation, was used to explore the scale effect of thermal cracking of rock under the thermal–mechanical coupling loading. The patterns and characteristics of thermal destruction were analyzed by simulating the thermal cracking of rocks with the same diameter different lengths, the same length but different diameters, and the same size ratio but different sizes (same length/diameter ratio but with different diameters). The acoustic emission and energy changes were also studied during thermal destruction. The results represented that the main forms of thermal cracking are tensile failure and shear failure. The smaller the scale is (length, diameter, and size), the more complex the pattern of thermal damage exhibited as failure patterns of inverted “S” or “V.” With the increasing scale, thermal damage models were simpler. The elastic modulus was determined by the diameter of specimens, and the peak stress was determined by the length of specimens. Overall, as the scale increased, the stress intensity decreased, but the number of acoustic emissions and acoustic emission energy and the corresponding accumulation increased.

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.

Digital Image-Based Model for Concrete Fracturing Process Analysis

2011 ◽  
Vol 704-705 ◽  
pp. 980-988
Author(s):  
Qing Lei Yu ◽  
Tian Hong Yang ◽  
Wan Cheng Zhu ◽  
Chao Zheng
Keyword(s):  
Digital Image ◽  
Numerical Models ◽  
Process Analysis ◽  
Failure Process ◽  
Scale Level ◽  
Actual Distribution ◽  
Processing Technologies ◽  
Proposed Model ◽  
Fracturing Process ◽  
Cracking Pattern

Concrete is a heterogeneous composite material. The heterogeneity consists of the distribution and shape of aggregate, interfacial transition zone (ITZ) and the inhomogeneity of each component materials. The key in numerical models for simulating the fracture behaviors is how to describe the heterogeneity actually. In this paper, at meso-scale level general-purposed digital image processing technologies are utilized to characterize the heterogeneity resulting from the shape and distribution of aggregates and ITZ, and at micro-scale level, a statistical method (e.g. Weibull distribution) is used to describe the heterogeneity of each phase. And then a multi-scale numerical model based on digital image is proposed to simulate fracturing process of concrete under loading condition. The proposed model can take the actual distribution and shape of aggregate into account. The fracturing process of concrete in uniaxial compressive tests is simulated by using the model. The results show that the shape of aggregates plays an important role in stress distributions to influence the damage evolution during loading. The proposed model is capable of capturing the complete failure process of concrete materials that includes the initiation, propagation and coalescence of microcracks as well as cracking pattern associated with different loading stages, which is a new tool to study the fracturing behaviors of concrete in more detail. Key words: digital image; heterogeneity characterization; fracturing process; concrete

scholarly journals Influence of water-soaking time on the acoustic emission characteristics and spatial fractal dimensions of coal under uniaxial compression

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 327-334 ◽  
Author(s):  
Zheqiang Jia ◽  
Li Ren ◽  
Qiangying Liu ◽  
Yuan Peng ◽  
Duo Xu ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Dimensionality Reduction ◽  
Uniaxial Compression ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Fractal Dimensions ◽  
Soaking Time ◽  
Reduction Model ◽  
Influence Of Water ◽  
Fracture Damage

The water-soaking time affects the physical and mechanical properties of coals, and the temporal and spatial evolution of acoustic emissions reflects the fracture damage process of rock. This study conducted uniaxial compression acoustic emissions tests of coal samples with different water-soaking times to investigate the influence of water-soaking time on the acoustic emissions characteristics and spatial fractal dimensions during the deformation and failure process of coals. The results demonstrate that the acoustic emissions characteristics decrease with increases in the water-soaking time. The acoustic emissions spatial fractal dimension changes from a single dimensionality reduction model to a fluctuation dimensionality reduction model, and the stress level of the initial descending point of the fractal dimension increases. With increases in the water-soaking time, the destruction of coal transitions from continuous intense failure throughout the process to a lower release of energy concentrated near the peak strength.

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