scholarly journals Research on crack evolution law and macroscopic failure mode of joint Phyllite under uniaxial compression

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiangbo Xu ◽  
Dongyang Fei ◽  
Yanglin Yu ◽  
Yilun Cui ◽  
Changgen Yan ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Stress Level ◽  
Joint Effect ◽  
Crack Evolution ◽  
Evolution Law ◽  
Joint Inclination ◽  
Original Crack

AbstractIn order to explore the fracture mechanism of jointed Phyllite, the TAJW-2000 rock mechanics test system is used to carry out uniaxial compression tests on different joint inclination Phyllites. The influence of joint inclination of Phyllite failure mode is discussed, and the progressive failure process of Phyllite is studied. The test results show that the uniaxial compressive strength anisotropy of jointed Phyllite is remarkable. As the inclination increases, it exhibits a U-shaped change; When 30° ≤ α ≤ 75°, the tensile and shear failures along the joint inclination mainly occurs. the joint inclination controls the failure surface form of the Phyllite; The crack initial stress level of the joint Phyllite is 0.30–0.59σf, the crack failure stress level is 0.44–0.86σf. When α = 90°, the σcd value is the largest, and σcd with α = 90° can be used as the maximum reliable value of uniaxial compressive strength of Phyllite. Using the theory of fracture mechanics, it is analyzed that under uniaxial compression of the rock, the crack does not break along the original crack direction, but extends along the direction at a certain angle to the original crack. The joint effect coefficient is proposed to show the influence of the joint inclination on the uniaxial compressive strength of the phyllite. Both the test and simulation results show that when the joint inclination is 60°, the joint effect coefficient is the largest. The compressive strength is the smallest. Numerical simulation analyses the crack evolution law of phyllite under different joint inclination under uniaxial compression, which verifies that there are different failure modes of joint phyllite under uniaxial compression.

Numerical investigation of micro-cracking behavior of brittle rock containing a pore-like flaw under uniaxial compression

2020 ◽  
Vol 29 (10) ◽  
pp. 1543-1568 ◽  
Author(s):  
Louis Ngai Yuen Wong ◽  
Jun Peng
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Numerical Model ◽  
Crack Initiation ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Early Stage ◽  
Brittle Rock ◽  
Cracking Behavior ◽  
Cracking Process

Pore-like flaws, which are commonly encountered in brittle rock, play an important role in the engineering performance of structures constructed in or on rock. Experimental and numerical investigations of micro-cracking mechanism of rock containing a pore-like flaw can enhance our knowledge of rock damage/failure from a microscopic view. In this study, the influences of a two-dimensional circular pore-like flaw with respect to its diameter and position on the strength and micro-cracking behavior of brittle rock under uniaxial compression are numerically investigated. The results reveal that the strength and elastic modulus are significantly affected by the diameter and position in the pore. The uniaxial compressive strength and elastic modulus of the numerical model with a pore diameter of 15.44 mm located in the center of the model are found to decrease by 58.6% and 56.4% respectively when compared with those of the intact model without a pore. As the pore position varies while the porosity remains unchanged, the simulated uniaxial compressive strength and elastic modulus are also found to be generally smaller than those of the intact model without a pore. When a pore-containing numerical model is loaded, the micro-cracks are found to mostly initiate at the top and bottom of the pore, due to the local tensile stress increase. The simulation results of the early-stage micro-cracking process and stress distribution are in a generally good agreement with the analytical solution obtained from the Kirsch equations. The grain-based model used in this study can not only study the crack initiation on the boundary of the pore but also provide a convenient means to analyze and visualize the temporal and spatial micro-cracking process after the crack initiation, which accounts for the variations in the simulated strength and modulus satisfactorily from a micro-cracking view.

Experimental Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

2012 ◽  
Vol 232 ◽  
pp. 24-27
Author(s):  
Zong Zhan Li ◽  
Jun Lin Tao ◽  
Yi Li
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Loading Rate ◽  
Testing Machine ◽  
Peak Stress ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

Study on Damage of Rock Samples with Single-Hole under Uniaxial Compression Condition

2012 ◽  
Vol 446-449 ◽  
pp. 3810-3813
Author(s):  
Bing Xie ◽  
Huai Feng Tong ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Compression Tests ◽  
Rock Samples ◽  
Single Hole ◽  
Compression Condition

Numerical specimens with single-hole is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that uniaxial compressive strength of specimen with single hole is less than complete specimens. As the holes move to the end of specimen, the uniaxial compressive strength first increases and then tends to decrease.

scholarly journals Experimental study on creep characteristics of infiltrated coal-rock under load

2021 ◽  
Author(s):  
Huimei Zhang ◽  
fuyu wang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Water Content ◽  
Uniaxial Compressive Strength ◽  
Stress Level ◽  
Water Infiltration ◽  
Creep Properties ◽  
Whole Process ◽  
Rock Creep ◽  
Coal Rock

Abstract For the water-rich zone in the coal tunnel rock body perennial suffer from water infiltration destabilization destruction problem.In this paper, the influence of stress level and infiltration time on the creep properties of coal-rock was systematically studied after the water infiltration test, scanning electron microscope(SEM), water content test, uniaxial compressive strength test and creep mechanical properties test.The whole process of coal-rock creep is described by Hooke's body, Kelvin body and damage elastic-plastic body, and the total damage variable was introduced to show the weakening effect of the coupling effect of stress and water infiltration on the creep properties of coal-rock.A creep constitutive model of coal rock damage considering the weakening effect of water infiltration was established, besides, the influence law of stress level and infiltration time on creep parameters of coal rock was analyzed.The study shows that coal rocks underwent a process from surface drying and shrinkage to water absorption and swelling to water-filled infiltration damage in the infiltration test.With the increase of infiltration time, the water content of coal-rock tended to increase and eventually stabilizes, while the uniaxial compressive strength gradually decreased.With the increase of stress level and infiltration time, the stable creep strain of coal-rock kept increasing which accelerated creep advance, and its internal damage continued to accumulate and eventually led to destabilization damage.At the same stress level, the creep parameter E0 showed a tendency to increase and then decreased with the increase of infiltration time, while E1, η1, tF, E2 and ν continued to decrease.Combined with the microstructural changes of coal rocks in the water infiltration process, the change law of mechanical properties of infiltrated coal-rock and the intrinsic softening mechanism were revealed.Comparing the theoretical model of infiltrated coal rock creep with the experimental data, the model developed in this paper reflected the whole process of infiltrated coal-rock creep deformation and damage, and can characterize the influence of infiltration time and stress level on coal-rock creep properties, which verified the reasonableness of the model.

scholarly journals Study of Strength and Deformation Evolution in Raw and Briquette Coal Samples under Uniaxial Compression via Monitoring Their Acoustic Emission Characteristics

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Han Meng ◽  
Yuzhong Yang ◽  
Liyun Wu ◽  
Fei Wang ◽  
Lei Peng
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Brittle Failure ◽  
Poisson’S Ratio ◽  
Cement Content ◽  
Poisson's Ratio ◽  
Ae Signal

Briquette coals with different cement contents are frequently used to study the coal body’s properties. In this study, the deformation and strength of briquette coal samples with 0, 5, 10, and 20% cement contents were experimentally and theoretically investigated using the acoustic emission (AE) characteristics monitored during the uniaxial compression tests. The results show that the uniaxial compression process of raw coal and briquette coal samples can be subdivided into compaction, elastic, plastic (yield), and brittle failure stages. With an increase in cement content, briquette coal samples undergo the elastic and plastic stages, and their postpeak stress drop rate gradually grows, and their plastic deformation is followed by brittle failure. The uniaxial compressive strength and elastic modulus of briquette coal samples show a linearly increasing relationship with cement content, while their Poisson’s ratio decreases gradually. During the uniaxial compression, raw coal and briquette coal samples produce the AE signals. The overall AE signal of briquette coal samples is relatively low, and there are no obvious AE events in raw coal samples. The uniaxial compressive strength, elastic modulus, and Poisson’s ratio of briquette coal samples with a 20% cement content and their AE signal cumulative amplitude, count, and energy values are very close to the corresponding parameters of raw coal samples. Therefore, they can be used for simulating raw coal samples in laboratory tests.

The effect of cross-section shape on deformation, damage and failure of rock-like materials under uniaxial compression from both a macro and micro viewpoint

2020 ◽  
Vol 29 (7) ◽  
pp. 1076-1099 ◽  
Author(s):  
Chunyang Zhang ◽  
Hang Lin ◽  
Caimou Qiu ◽  
Tingting Jiang ◽  
Jianhua Zhang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Cross Section ◽  
Peak Strength ◽  
Experimental Results ◽  
Cross Sectional ◽  
Damage And Failure ◽  
Section Shape

The mechanical properties of rock-like materials always attract the interest of many researchers. In this paper, we study the influence of specimen cross-section shape on uniaxial compressive strength as well as their deformation, damage and failure characteristics by uniaxial compression tests. The diameter and height of circular cross-section specimens are 50 and 100 mm, respectively, and the height and cross-sectional area of other specimens are equal to that of circular cross-sectional ones. Simulation and experimental results show that the cross-sectional shape has little effect on uniaxial compressive strength. Moreover, the effect on other mechanical properties is also very limited before the peak strength, such as stress–strain curve, rotation and motion of particles, contact damage and energy evolution of particles; however, it gradually becomes obvious after the peak strength. This is a very important feature, which affects the macroscopic form of failure of specimens and reflects the difference between failure surfaces. The shapes of failure surfaces obtained from numerical simulations are quite similar to the experimental results, which verify the reliability of numerical simulation results. Finally, the achievements can serve as a reference for related engineering issues.

Influence of Loading Rate on Uniaxial Compression Test of Rock Specimen with Random Joints

2011 ◽  
Vol 396-398 ◽  
pp. 217-220
Author(s):  
Bing Xie ◽  
Jin Jun Guo ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Compression Test ◽  
Rock Specimen ◽  
Loading Rate ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Compression Tests

Numerical specimens with ramdom joints is established by particle flow code PFC2D and uniaxial compression tests are conducted under three different loading rate. Studies have shown that strength of uniaxial compression are all increased with the loading rate no matter what specimen is complete or with random joints. The sensitivity of changes of uniaxial compressive strength of specimen with random joints decreases with increasing of the loading rate.

Numerical Study on Uniaxial Compression Test of Rock Specimen with Random Holes

2011 ◽  
Vol 418-420 ◽  
pp. 848-850
Author(s):  
Bing Xie ◽  
Li Guo ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Compression Test ◽  
Rock Specimen ◽  
Numerical Study ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Compression Tests

Numerical specimens with ramdom holes is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that the uniaxial compressive strength of the specimen accelerated decline while the porosity increasing uniformly. With the increasing of the porosity，the plastic of the specimen increases.

A Statistical Analysis of First-Year Level Ice Uniaxial Compressive Strength in the Svalbard Area

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Lucie Strub-Klein
Keyword(s):  
Compressive Strength ◽  
Statistical Analysis ◽  
Failure Mode ◽  
Uniaxial Compressive Strength ◽  
Barents Sea ◽  
Field Investigation ◽  
Visual Observation ◽  
The Arctic ◽  
Sample Orientation ◽  
Level Ice

This paper proposes a methodology for a statistical analysis of uniaxial compressive strength and applies it to full-scale data collected in the Svalbard area from 2005 to 2011. A total of 894 samples were compressed over 7 years of field investigation. The ice was mainly from frozen fjords on Svalbard and also from the Barents Sea and the Arctic Ocean. The analysis consisted in determining the most appropriate distribution for level ice strength according to the sample orientation, the time of the year (which would then relate to the brine configuration in the ice), and the failure mode. Six groups (horizontal, vertical, early, late, brittle, and ductile) were defined, and the gamma, two-parameter Weibull, and lognormal distributions were compared for each group. The Weibull parameters (shape and scale) were estimated with the method of moments and the method of maximum likelihood. The two methods agreed well. A visual observation of quantiles–quantiles plots (QQ-plots) combined with a linear regression and a Kolmogorov–Smirnov (KS) test were conducted to determine the best fitting distribution. Neither the season nor the failure mode appeared to influence the determination of a statistical distribution, contrary to the sample orientation. However, it appeared that the lognormal distribution was a best fit for the failure mode and season groups, whereas the gamma and the Weibull were the best candidates for the vertical and horizontal samples, respectively.

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