scholarly journals Effect of the Interaction between Cavities and Flaws on Rock Mechanical Properties under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Jianwang Li ◽  
Yu Zhou ◽  
Wei Sun ◽  
Zheng Sun
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Three Dimensional ◽  
Strain Curve ◽  
Ct Scanning ◽  
Two Dimensions ◽  
Particle Flow Code ◽  
Uniaxial Compression Test ◽  
Fracture Evolution ◽  
Microcrack Propagation

Cavities and flaws are common types of defects in rock specimens that have an important impact on the mechanical properties of rockmass. In this paper, cement mortar was used to prefabricate a rock-like specimen with two cavities and a single flaw, and the uniaxial compression test was carried out. The process of fracture evolution on the specimen surface was obtained by using photography technology. The evolution regularity of a fracture was monitored by utilizing acoustic emission (AE) technology during the process of the specimen failure. Moreover, three-dimensional (3D) tomograms of specimens after uniaxial compression were obtained by using computerized tomography (CT) scanning technology, investigating the development characteristics of microcracks and the distribution of the final macrofractures. The particle flow code in two dimensions (PFC2D) program was used to simulate the mechanical behavior of brittle rock combining with microcrack propagation. The calculated stress-strain curve, AE features, and fracture distribution of the specimen obtained from the PFC2D simulation were relatively consistent with the experimental results.

scholarly journals Investigation of the Effect of Bedding Layer Angle and Tunnel Number on the Stability of Tunnel under Uniaxial Compression Using PFC2D

2021 ◽  
Author(s):  
Vahab Sarfarazi ◽  
Kaveh Asgari ◽  
Mahdiyah Azizian
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Dominant Mode ◽  
Two Dimensions ◽  
Particle Flow Code ◽  
Concrete Layer ◽  
Tunnel Diameter ◽  
Tunnel Number ◽  
Crack Growth Path ◽  
The Stability

In this paper the effect of bedding layer angle on the stability of tunnel under uniaxial compression have been investigated using particle flow code in two dimensions (PFC2D). For this purpose, numerical rectangle models with dimension of 100*100 mm have been prepared. These models consist of layers with different mechanical properties i.e., concrete layer and gypsum layer. The angle of these layers related to horizontal axis change from 0° to 90° with increment of 15°. These models are consisting of one, two and three tunnel. The diameter of tunnel change based on the tunnel number. The tunnel diameter was 6 m, when one tunnel exists in the model. The tunnel diameter was 3 m, when two tunnels exist in the model. The tunnel diameter was 2 m, when three tunnels exist in the model. These models were subjected to uniaxial compression. The results show that tensile cracks are dominant mode of fracture occurred in the models. The joint angle and tunnel number have important effect on the failure pattern and failure strength. Also, the mechanical properties of beddings control the crack growth path. The crack grows through the weak layers when bedding angle was equal to 45° and 60°, but it intersects the layer for any other bedding angels.

scholarly journals Three-Dimensional Reconstruction and Numerical Simulation Analysis of Acid-Corroded Sandstone Based on CT

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zizhen Miao ◽  
Shuguang Li ◽  
Jiangsheng Xie ◽  
Runke Huo ◽  
Fan Ding ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Simulation Analysis ◽  
Acid Corrosion ◽  
Three Dimensional ◽  
Strain Curve ◽  
Uniaxial Compression Test ◽  
Evolution Law ◽  
Simulation Results

Due to its unique technological characteristics, coal mining and production often encounter an acid corrosion environment caused by acid gases. Acid erosion and a series of chemical reactions caused by it often led to the deterioration of coal, rock, support structure, etc. and induced serious safety accidents. To further explore the macro-mesoscopic damage evolution law and failure mechanisms of rock masses under corrosion conditions through numerical simulation, a zonal refined numerical model that can reflect the acid corrosion characteristics of sandstone is established based on CT and digital image processing (DIP). The uniaxial compression test of corroded sandstone is simulated by ABAQUS software. Comparing the numerical simulation results with the physical experiment results, we found that the three-dimensional finite element model based on CT scanning technology can genuinely reflect sandstone’s corrosion characteristic. The numerical simulation results of the stress-strain curve and macroscopic failure mode of the acid-corroded sandstone are in good agreement with the experimental results, which provides a useful method for further studying the damage evolution mechanism of the acid-corroded rock mass. Furthermore, the deformation and damage evolution law of the corroded sandstone under uniaxial compression is qualitatively analyzed based on the numerical simulation. The results show that the rock sample’s axial displacement decreases gradually from top to bottom under the axial load, and the vertical variation is relatively uniform. In contrast, the rock sample’s removal gradually increases with the increase of axial pressure, and the growth presents a certain degree of nonuniformity in the vertical. The acid-etched rock sample’s damage starts from both the end and the middle; it first appears in the corroded area. Moreover, with the displacement load increase, it gradually develops and is merged in the middle of the rock sample and forms macroscopic damage.

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 Evaluation Method of Granite Multiscale Mechanical Properties Based on Nanoindentation Technology

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Man Lei ◽  
Fa-ning Dang ◽  
Haibin Xue ◽  
Mingming He
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Evaluation Method ◽  
Poisson Ratio ◽  
Nanoindentation Test ◽  
Uniaxial Compression Test ◽  
Displacement Curve ◽  
Mineral Contents

In order to study the mechanical properties of granite at the micro- and nanoscale, the load-displacement curve, residual indentation information, and component information of the quartz, feldspar, and mica in granite were obtained using a nanoindentation test, a scanning electron microscope (SEM), and X-ray diffraction (XRD). The elastic modulus and the hardness of each component of the granite were obtained through statistical analysis. Treating rock as a composite material, the relation between the macro- and microscopic mechanical properties of rock was established through the theory of micromechanical homogenization. The transition from micromechanical parameters to macromechanical parameters was realized. The equivalent elastic modulus and Poisson’s ratio of the granite were obtained by the Self-consistent method, the Dilute method, and the Mori-Tanaka method. Compared with the elastic modulus and the Poisson ratio of granites measured by a uniaxial compression test and the available data, the applicability of the three methods were analyzed. The results show that the elastic modulus and hardness of the quartz in the granite is the largest, the feldspar is the second, the mica is the smallest. The main mineral contents in granite were analyzed using the semiquantitative method by XRD and the rock slice identification test. The elastic modulus and the Poisson ratio of granite calculated by three linear homogenization methods are consistent with those of the uniaxial compression test. After comparing the calculation results of the three methods, it is found that the Mori-Tanaka method is more suitable for studying the mechanical properties of rock materials. This method has an important theoretical significance and practical value for studying the quantitative relationship between macro- and micromechanical indexes of brittle materials. The research results provide a new method and an important reference for studying the macro-, micro-, and nanomechanical properties of rock.

Research of Inclination Angle Effect on Joint Rock Macromechanical Parameters

2011 ◽  
Vol 704-705 ◽  
pp. 1089-1094
Author(s):  
Yan Feng Feng ◽  
Tian Hong Yang ◽  
Hua Wei ◽  
Hua Guo Gao ◽  
Zhe Zhang
Keyword(s):  
Rock Mass ◽  
Uniaxial Compression ◽  
Inclination Angle ◽  
Damage Mechanics ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Uniaxial Compression Test ◽  
Joint Rock Mass ◽  
Test Result ◽  
Joint Rock

The joint of rock mass influences and controls the rock mass intensity, deformation characteristics and instability failure in the rock engineering to a great extent. Using the similar material simulation is of different inclination angle of non-penetration jointing and non-jointing rock mass, through using rigid servo compression machine to carry uniaxial compression test, we get a nearly same trend of joint rock mass stress-strain curve of different angle, the curve of inclination angle of 45 is analyzed, the test result shows that the compressive strength first decreases and then increases gradually with the increase of rock inclination angle. The compression intensity is its minimum when of the inclination angle of 45°, and the deformation modulus first decreases and then increases, but deformation modulus of 30° is its minimum. In addition, through the use of developed RFPA2D system to simulate on trial uniaxial compression value based on microscopic damage mechanics, we get the conclusion that the numerical analysis and test result is fitting approximately, it is validated that the numerical model can simulate joint rock well. Keywords: joint rock mass, inclination angle, uniaxial compression, compressive intensity, deformation modulus

scholarly journals Experimental Study on Influence of Microexpansive Concrete Self-Stress on Performance of Steel Pipe Concrete

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xin Liu ◽  
Yu-Zhou Zheng ◽  
Qin Fang ◽  
Heng-Bo Xiang ◽  
Hai-Chun Yan
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Steel Tube ◽  
Diameter Ratio ◽  
Expansion Rate ◽  
Uniaxial Compression Test ◽  
Expansive Agent ◽  
Short Columns ◽  
Length To Diameter Ratio

To explore the influence of microexpansive concrete self-stress on the performance of steel pipe concrete, the expansion rate test of microexpansive concrete confined by steel tube was carried out with different expansion rates. Then, the mechanical properties of high-strength steel tube-confined microexpansive concrete (HSTCMC) short columns were conducted by the uniaxial compression test. The length-to-diameter ratio, the expansion rate of the microexpansive concrete, and the steel tube thickness were investigated in the study. Furthermore, the ABAQUS software was employed to analyze the microexpansive mechanism of the concrete, and it was verified by the uniaxial compression test. The test results show that the concrete possesses a remarkable volume expansion phenomenon, which was up to 150 με after four days of maintenance time. The mechanical properties of the HSTCMC short columns were greatly improved compared to the control RC pier. The yield and ultimate strength of the HSTCMC short columns can be enhanced to 8.9% and 14.6%, and with the content of expansive agent that increased from 8% to 12%. The finite element analysis results highlighted that the end constraint at the two ends has the biggest influence on the mechanical performance of the HSTCMC short columns, followed by the thickness of the steel tube and the content of the expansive agent. It should be noted that the self-stress of microexpansive concrete will be decreased with the increase in the length-to-diameter ratio, when the length-to-diameter ratio is less than four. Furthermore, the constraint effect of the circular steel tube on the microexpansive concrete is better than that of the rectangular section steel tube.

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