scholarly journals Acoustic-Mechanical Responses of Intact and Flaw-Contained Rock Deformation under Uniaxial Compression: A Comparison

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Gui-Lin Wang ◽  
Liang Zhang ◽  
Zhen Wang ◽  
Jian-Zhi Zhang ◽  
Fan Sun ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Fracture Behavior ◽  
Failure Modes ◽  
Jointed Rock ◽  
Peak Strain ◽  
Rock Masses ◽  
Stress Jump ◽  
Loading Process ◽  
Monitoring Technique

The study of the mechanical properties and cracking behaviors of jointed rock masses is important in rock engineering projects. In the present study, a series of uniaxial compression experiments were conducted on intact rock, and rock masses with single or double preexisting flaws, and then the strength, deformability, and fracture behavior of samples are investigated. Moreover, photographic monitoring technique and emission monitoring technique are introduced to explore the fracturing mode and the acoustic emission (AE) evolution characteristic of fractured rock during the whole loading process. The obtained results show that the preexisting flaw has a strong influence on the mechanical properties, fracture behavior, and AE characteristic of sandstone specimens. In detail, the stress-strain curves show that no significant stress jump occurs at prepeak and postpeak points for intact sandstone specimens; however, the flaw-contained sandstone specimens exhibit distinct stress jump during the entire loading process. Meanwhile, the strength parameters of the the rock specimen is obviously weakened by the preexisting fissures, and the uniaxial compression strength of rock specimens generally decreases with the increase in the number of preexisting fissure as well as the peak strain and the elastic modulus. The failure modes of intact and flaw-contained sandstone specimens exhibit the splitting failure and the mixed failure modes of shear and tension, respectively. Similarly, the maximum AE counts and AE energy both decrease with the increasing number of preexisting flaw. The present research can enhance the understanding of mechanical properties, cracking behaviors, and failure mechanism of jointed rock mass.

scholarly journals Numerical Study of the Strength and Characteristics of Sandstone Samples with Combined Double Hole and Double Fissure Defects

2021 ◽  
Vol 13 (13) ◽  
pp. 7090
Author(s):  
Junbiao Ma ◽  
Ning Jiang ◽  
Xujun Wang ◽  
Xiaodong Jia ◽  
Dehao Yao
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Compressive Stress ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Numerical Study ◽  
Simulation Software ◽  
Particle Flow Code ◽  
Peak Strain

To explore the failure mechanism of rock with holes and fissures, uniaxial compression tests of sandstone samples with combined double hole and double fissure defects were carried out using Particle Flow Code 2D (PFC2D) numerical simulation software. The failure behaviour and mechanical properties of the sandstone samples with combined double hole and double fissure defects at different angles were analysed, and the evolution results of the stress field and crack propagation were studied. The results show that with a decrease in fissure angle, the crack initiation stress, damage stress, elastic modulus and peak stress of the defective rock decrease, while the peak strain increases, and the brittleness of the rock is weakened. Rocks with combined double hole and double fissure defects at different angles lead to different failure modes, crack initiation positions and crack development directions. After uniaxial compression, both compressive stress and tensile stress concentration areas are produced in the defective rock, but the compressive stress concentration is of primary importance. The concentration area is mainly distributed around the holes and fissures and the defect connecting line, and the stress concentration area decreases with the decreasing fissure angle. This study can correctly predict the mechanical properties of rock with combined double hole and double fissure defects at different angles and provide a reference for actual rock engineering.

scholarly journals Mechanical and failure characteristics of rock-like material with multiple crossed joint sets under uniaxial compression

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770871 ◽  
Author(s):  
Jiaming Liu ◽  
Shaorui Sun ◽  
Ling Yue ◽  
Jihong Wei ◽  
Jimin Wu
Keyword(s):  
Compressive Strength ◽  
Young’S Modulus ◽  
Uniaxial Compression ◽  
Unconfined Compressive Strength ◽  
Failure Modes ◽  
Young's Modulus ◽  
Jointed Rock ◽  
Rock Masses ◽  
Joint Spacing ◽  
Jointed Rock Masses

The strength and deformation of rock masses transected by persistent joints are controlled by the fracture network. In this work, bonded particle model modeled by particle flow code in three dimensions was used to study the effect of geometry parameters on the strength and behavior of jointed rock masses under uniaxial compression. The effect of the number of crossed joint sets, joint orientation, and joint spacing on the uniaxial compressive strength was investigated, and this article presents the results of the numerical simulations. Rigorous validation process had done before the numerical experiments. Four types of blocks (Series A, B, C, and D) with different numbers of joint sets were considered in this article. Then, a sensitivity study is undertaken to investigate the effects of joint set numbers and joint geometry configuration on the failure mode, unconfined compressive strength, and Young’s modulus of jointed rock mass. The interaction among the crossed joint sets was found to have marked effects on the mechanical properties and failure modes. A study about the effects of joint spacing on the failure modes, unconfined compressive strength, and Young’s modulus was also conducted. Joint spacing was found to have no significant effect on the failure modes of jointed rock masses in a certain range. It is also shown that the range and variance of unconfined compressive strength are affected principally by joint set numbers and decreased slightly with the decrease in joint spacing. The effect of crossed joint sets on the stress field was carried out. Stress concentration was found to be the reason for relatively lower strength of blocks with crossed joint sets compared to the block with the same weakest single joint set. The result in this article is of great help to reveal the mechanism of damage and fracture of jointed rocks under uniaxial compression.

scholarly journals Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression

Energies ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 200
Author(s):  
Zhongliang Feng ◽  
Xin Chen ◽  
Yu Fu ◽  
Shaoshuai Qing ◽  
Tongguan Xie
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Failure Modes ◽  
Strain Curve ◽  
Particle Flow Code ◽  
Rock Masses ◽  
Physical Experiments ◽  
Inclination Angles ◽  
Joint Inclination

The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.

scholarly journals Effects of Temperature and Water on Mechanical Properties, Energy Dissipation, and Microstructure of Argillaceous Sandstone under Static and Dynamic Loads

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Rongrong Zhang ◽  
Dongdong Ma ◽  
Qingqing Su ◽  
Kun Huang
Keyword(s):  
Mechanical Properties ◽  
Energy Dissipation ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Physical And Mechanical Properties ◽  
P Wave ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Sandstone Specimen

RMT-150B rock mechanics and split Hopkinson pressure bar (SHPB) devices were adopted to investigate the physical and mechanical properties, energy dissipation, and failure modes of argillaceous sandstone after different high temperatures under air-dried and saturation states. In addition, SEM and EDS tests were conducted to investigate its microstructure characteristics. Results showed that both the P-wave velocity and density of argillaceous sandstone specimen decreased with the increase of high temperature, while its porosity increased. Compared with static stress-strain curves, there was no obvious compaction stage for dynamic stress-strain curves, and the decrease rate of dynamic curves after peak strain was obviously slow compared with static curves. Both the static and dynamic strengths of argillaceous sandstone specimens decreased with increasing temperature, and the critical temperature point for the strength of argillaceous sandstone was 400°C. At the same temperature, the specific energy absorption under air-dried state was generally smaller compared with that under saturated state. Both the strain rate and temperature showed significant effect on the failure mode. After 100∼1000°C heat treatment, the granular crystals of the clastic structure gradually became larger, and both the number and average size of the original pores decreased, resulting in the deterioration of mechanical properties of argillaceous sandstone specimen.

Experimental Study on Strength of Rock Masses with Transfixion Joint under Uniaxial Compression

2013 ◽  
Vol 353-356 ◽  
pp. 856-859
Author(s):  
Lei Wang ◽  
Shi Chen Li ◽  
Jian Xin Han ◽  
Zhong Yi Zeng
Keyword(s):  
Uniaxial Compression ◽  
Testing Machine ◽  
Jointed Rock ◽  
Servo Control ◽  
Peak Strength ◽  
Rock Masses ◽  
Peak Intensity ◽  
Standard Specimens ◽  
Joint Inclination ◽  
The Relationship

The relationship between the peak strength of rock masses and joint inclination angle is closely, to study its relationship, experiment on pre-existing persistent jointed rock cylindrical standard specimens was made under uniaxial compression by high stiffness servo control testing machine, experiment found that: the residual peak intensity and peak strength are increased with the decrease of jointed and nonlinear. Analysis on the peak intensity changing with the fissure inclination using Kulun strength theory, theory analysis conclusion is consistent with the experiment, prove the conclusions of experiments and theoretical analysis all can reflect the law of rock masses with transfixion joint failure strength well.

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