scholarly journals Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Numbers

2021 ◽  
Author(s):  
Y L Wang ◽  
D S Liu ◽  
K Li ◽  
D Chen ◽  
X M Hu
Keyword(s):  
Mechanical Characteristics ◽  
Failure Modes ◽  
Three Dimensional ◽  
Strain Curve ◽  
Uniaxial Compression Test ◽  
Rock Masses ◽  
Deformation And Failure ◽  
Deformation Features ◽  
Low Strength ◽  
Strength Rock

The mechanical characteristics and failure modes of low-strength rock sample with various crack dip angles and numbers were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the number of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down and horizontally extended decline, respectively, showing obvious ductility and ductile-flow deformation and failure characteristics. Due to the structural effect, only under the condition of fissure α < 90°, the modulus of peak strength and elastic modulus lowered with the enhancement of fissure number and had a negative correlation. As the number of fissures increased, the axial peak strain increased first and then decreased, demonstrating a reversed V-shaped change trend. Fissure number can fully affect the crack propagation law only in the case of vertical fissures. The above research findings can complement and improve the study of fissured rock masses.

scholarly journals Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Dip Angles

2021 ◽  
Author(s):  
Y L Wang ◽  
D S Liu ◽  
K Li ◽  
X M Hu ◽  
D Chen
Keyword(s):  
Rock Mass ◽  
Mechanical Characteristics ◽  
Failure Modes ◽  
High Strength ◽  
Rock Masses ◽  
Deformation And Failure ◽  
Deformation Features ◽  
Low Strength ◽  
Dip Angle ◽  
Strength Rock

The mechanical characteristics and failure modes of low-strength rock sample with various fissure dip angles were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the dip angle of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down, showing obvious ductility deformation and failure characteristics. Peak strength and elastic modulus owned an anti-S-shaped growth tendency with the growth of fissure dip angle, which was positively correlated and greatest subtle to the fissure dip angle α < 21° and α > 66.5°. The axial peak strain reduced first and enlarged rapidly with growing fissure dip angle, suggesting a V-shaped change trend. Increasing the fissure dip angle will change the sample failure mode, experienced complete tensile failure to tensile-shear composite failure, and ultimately to typical shear failure. Also, the crack start angle decreased with enlarging fissure dip angle, larger than that the high-strength rock mass fissure dip angle. The above research findings can complement and improve the study of fissured rock masses.

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 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.

Three Dimensional Numerical Analysis of Deformation and Stability of Zone II of Xiazanri Slope Deposit

2011 ◽  
Vol 90-93 ◽  
pp. 2372-2379
Author(s):  
Li Fang Zou ◽  
Wei Ya Xu ◽  
Chong Shi
Keyword(s):  
Large Scale ◽  
Failure Modes ◽  
Three Dimensional ◽  
Left Bank ◽  
Failure Characteristics ◽  
Deformation And Failure ◽  
Geological Conditions ◽  
Normal Water ◽  
Zone Ii ◽  
Very High

Xiazanri Slope is a large-scale deposit slope located at the left bank of Liyuan hydropower station in Southwest China. The construction of the water intake there will form a very high excavation slope. Possible failure modes are analyzed based on geological conditions. Numerical simulation is conducted in FLAC3D to obtain the deformation and failure characteristics of slope under excavation and normal water table conditions. Strength reduction method is used to obtain factor of safety. Results show the overall deposit is stable and attention should be paid to local parts.

Experimental Study on Post-Peak Failure Behavior of Rock Masses with Persistent Joint

2014 ◽  
Vol 580-583 ◽  
pp. 610-613 ◽  
Author(s):  
Lei Wang ◽  
Jiang Yu ◽  
Xue Hua
Keyword(s):  
Inclination Angle ◽  
Failure Modes ◽  
Research Result ◽  
Peak Stress ◽  
Jointed Rock ◽  
Failure Behavior ◽  
Uniaxial Compression Test ◽  
Rock Masses ◽  
Stress Strain ◽  
Joint Inclination

The uniaxial compression test on pre-existing persistent jointed rock cylindrical standard specimen made by high stiffness servo control testing machine, systematic researched the relationship between jointed rock post-peak stress-strain curve, the destroy form of rock masses with dip angles of persistent joints. And the results reveal that: (1) The post-peak stress - strain curves of specimens with joint inclination angle of 15°and complete specimens are basically the same, but the difference of post-peak stress - strain curves of specimens with the joint inclination angle from 30°to 60°and complete specimens is vary greatly; (2) The post-peak failure modes of specimen change with different joint inclination. The research result can reflect mechanics and deformation and damage characteristics under uniaxial compressive loading in the phase of post-peak of rock masses with different dip angle pre-existing persistent joints.

scholarly journals Experimental Investigation on the Mechanical Characteristics and Deformation Behaviour of Fractured Rock-Like Material with One Single Fissure under the Conventional Triaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Taoli Xiao ◽  
Mei Huang ◽  
Cheng Cheng ◽  
Yunlong He
Keyword(s):  
Mechanical Characteristics ◽  
Failure Modes ◽  
Shear Failure ◽  
Early Stage ◽  
Fractured Rock ◽  
Deformation Behaviour ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Material Specimen

An experimental study was carried out on a rock-like material specimen containing a single fissure to investigate its mechanical characteristics and deformation behaviour under triaxial compression. The mechanical characteristics, such as peak strength and residual strength, are discussed. The confining pressure had a distinct effect on the ductility characteristics of the specimen. “A distinct stress drop” occurred in the early stage of the stress-strain curve when the length fissure was relatively long. The I-crack, II-crack, and III-crack are all observed under triaxial compression, and the III-crack is commonly observed under triaxial compression. Confining pressure plays an essential role in affecting the failure mode of the specimen. There are three kinds of failure modes in the triaxial compression experiment on a rock-like material specimen with one single fissure: tensile-shear comprehensive failure, “X”-shaped shear failure, and shear failure along the fissure plane. These results are important and fundamental to understand the fracture mechanism of rock engineering.

Numerical Analysis on the Evolutionary Features of Deformation and Failure Modes of Slope

2012 ◽  
Vol 204-208 ◽  
pp. 144-154
Author(s):  
Xiao Song Tang ◽  
Ying Ren Zheng ◽  
Hui Ming Tang
Keyword(s):  
Plastic Strain ◽  
Failure Modes ◽  
Sliding Surface ◽  
Deformation And Failure ◽  
Whole Process ◽  
Evolutionary Features ◽  
Slope Structure ◽  
Deformation Features ◽  
Gradual Accumulation ◽  
Rock And Soil

The failure of slope is a gradual accumulation process. Under the effect of many interior and exterior factors, some parts in the slope reach yield with the increase of stress; sliding surface forms gradually till complete transfixion; with the plastic strain continuous increases, overall failure happens on the slope. Traditional analysis method cannot display the mechanic conditions and the whole process of deformation, transfixion of sliding surfaces and failure. Meanwhile, FEM strength reduction can quantitatively show the deformation features and the process of occurrence and development of sliding surface. Based on the previous researches, the paper classifies slopes according to the features of rock and soil and the slope structure. Through analyzing the graphs of deformation and the nephograms of plastic strain under different reduction factors or safety factors, the researchers can directly find the deformation tendency of slopes and the whole process of the extension, transfixion and failure of sliding surface with the reduction of safety factor. So, the failure mechanism of slope can be found intuitively, which can provide effective basis for the prevention and governance of slopes.

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.

Scanning Electron Microscopy in Hybrid Microelectronics

1976 ◽  
Vol 34 ◽  
pp. 456-457
Author(s):  
S. Khadpe ◽  
R. Faryniak
Keyword(s):  
Integrated Circuits ◽  
Thick Film ◽  
Integrated Circuit ◽  
Failure Modes ◽  
Three Dimensional ◽  
Circuit Components ◽  
Hybrid Microcircuit ◽  
Electrical Connections ◽  
Scanning Electron

The Scanning Electron Microscope (SEM) is an important tool in Thick Film Hybrid Microcircuits Manufacturing because of its large depth of focus and three dimensional capability. This paper discusses some of the important areas in which the SEM is used to monitor process control and component failure modes during the various stages of manufacture of a typical hybrid microcircuit.Figure 1 shows a thick film hybrid microcircuit used in a Motorola Paging Receiver. The circuit consists of thick film resistors and conductors screened and fired on a ceramic (aluminum oxide) substrate. Two integrated circuit dice are bonded to the conductors by means of conductive epoxy and electrical connections from each integrated circuit to the substrate are made by ultrasonically bonding 1 mil aluminum wires from the die pads to appropriate conductor pads on the substrate. In addition to the integrated circuits and the resistors, the circuit includes seven chip capacitors soldered onto the substrate. Some of the important considerations involved in the selection and reliability aspects of the hybrid circuit components are: (a) the quality of the substrate; (b) the surface structure of the thick film conductors; (c) the metallization characteristics of the integrated circuit; and (d) the quality of the wire bond interconnections.

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