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 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 Particle Flow Code Simulation of the Characteristics of Crack Evolution in Rock-Like Materials with Bent Cracks

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhanguo Ma ◽  
Shixing Cheng ◽  
Peng Gong ◽  
Jun Hu ◽  
Yongheng Chen
Keyword(s):  
Elasticity Modulus ◽  
Gradual Increase ◽  
Simulation Method ◽  
Two Dimensions ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Crack Evolution ◽  
Underground Engineering ◽  
The Stability ◽  
The Impact

The distribution and propagation of rock cracks have a significant impact on geotechnical engineering. Taking rock-like materials with bent cracks as the research object, the particle flow code in two dimensions numerical simulation method was used to study the impact of the bend number on rock-like materials strength and crack evolution. According to the results, when the bend number was 1, 3, and 7, the strength of the specimens gradually increased; the elasticity modulus did not change significantly with the crack bend number. Uniaxial compression generated tensile cracks in all the specimens with bent cracks, but in terms of failure mode, the specimens with 0 bend tended to suffer penetrating failure along the fracture strike, while the specimens with 1, 3, and 7 bend tended to suffer penetrating failure along the diagonal direction. Both the fractal dimension and bend number were positively correlated with strain; with the gradual increase of the stress percentage, the damage variable of the specimens gradually increased at a growing rate. The research results provide a reference for predicting the stability of the underground engineering surrounding rocks containing bent cracks.

scholarly journals Mechanical Properties and Acoustic Emission Properties of Rocks with Different Transverse Scales

2017 ◽  
Vol 2017 ◽  
pp. 1-8
Author(s):  
Xi Yan ◽  
Li Jun ◽  
Liu Gonghui ◽  
Guo Xueli
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Compression Strength ◽  
Petroleum Engineering ◽  
Uniaxial Compression Strength ◽  
Emission Properties ◽  
Aspect Ratios ◽  
Transverse Scale ◽  
The Stability

Since the stability of engineering rock masses has important practical significance to projects like mining, tunneling, and petroleum engineering, it is necessary to study mechanical properties and stability prediction methods for rocks, cementing materials that are composed of minerals in all shapes and sizes. Rocks will generate acoustic emission during damage failure processes, which is deemed as an effective means of monitoring the stability of coal rocks. In the meantime, actual mining and roadway surrounding rocks tend to have transverse effects; namely, the transverse scale is larger than the length scale. Therefore, it is important to explore mechanical properties and acoustic emission properties of rocks under transverse size effects. Considering the transverse scale effects of rocks, this paper employs the microparticle flow software PFC2D to explore the influence of different aspect ratios on damage mechanics and acoustic emission properties of rocks. The results show that (1) the transverse scale affects uniaxial compression strength of rocks. As the aspect ratio increases, uniaxial compression strength of rocks decreases initially and later increases, showing a V-shape structure and (2) although it affects the maximum hit rate and the strain range of acoustic emission, it has little influence on the period of occurrence. As the transverse scale increases, both damage degree and damage rate of rocks decrease initially and later increase.

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 Failure Properties and Stability Monitoring of Strip and Column Cemented Gangue Backfill Bodies Under Uniaxial Compression In Constructional Backfill Mining

2022 ◽  
Author(s):  
Hongyu Ran ◽  
Yuxia Guo ◽  
Guorui Feng ◽  
Chunqing Li
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Constitutive Models ◽  
Peak Stress ◽  
Peak Strain ◽  
Height Ratio ◽  
Stability Monitoring ◽  
Backfill Mining ◽  
Failure Properties ◽  
The Stability

Abstract The strip and column cemented gangue backfill bodies (CGBBs) are the main supporting components in the design of constructional backfill mining for coal mining, which determines the stability of goaf. Previous researches have mostly focused on the mechanical properties of column CGBB, but the mechanical properties of strip CGBB are still unclear. Herein, the uniaxial compression experiments for strip and column CGBBs were conducted to compare the failure properties. The acoustic emission (AE) and two types of resistivity monitoring were used to monitor the damage evolution. The effect of the length-height ratio on the mechanical characteristic of strip CGBB was analyzed by discrete element simulation. The results show that: the strength and peak strain of strip CGBB under uniaxial compression is higher than those of column CGBB, and the strip CGBB shows better ductility. The stress of column CGBB decreases significantly faster than that of strip CGBB at the post-peak stage. The strength and ductility of strip CGBB increase with the increase of length-height ratio. The strip CGBB is destroyed from both ends to the middle under uniaxial compression, and the core bearing area is reduced correspondingly. The AE signal evolution of CGBBs under uniaxial compression before the peak stress contains three stages, and the AE signals of strip CGBB at the peak stress will not rise sharply compared with column CGBB. The resistivity monitoring effect of the horizontally symmetrical conductive mesh is better than that of the axial. The horizontal resistivity increases gradually with the increase of stress under uniaxial compression, and increases sharply at the peak stress, and then drops after the peak stress. The damage constitutive models and the stability monitoring models of the CGBBs are established based on the experimental results. This work would be instructive for the design and stability monitoring of CGBB.

An analysis of the transport properties and mechanical stability of rapidly solidified Al-Sb alloy

2015 ◽  
Vol 10 (2) ◽  
pp. 2663-2681
Author(s):  
Rizk El- Sayed ◽  
Mustafa Kamal ◽  
Abu-Bakr El-Bediwi ◽  
Qutaiba Rasheed Solaiman
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Melt Spinning ◽  
Elastic Moduli ◽  
Mechanical Stability ◽  
Microstructural Analysis ◽  
Alloy System ◽  
Antimony Content ◽  
The Stability ◽  
Rapidly Solidified

The structure of a series of AlSb alloys prepared by melt spinning have been studied in the as melt–spun ribbons  as a function of antimony content .The stability  of these structures has  been  related to that of the transport and mechanical properties of the alloy ribbons. Microstructural analysis was performed and it was found that only Al and AlSb phases formed for different composition.  The electrical, thermal and the stability of the mechanical properties are related indirectly through the influence of the antimony content. The results are interpreted in terms of the phase change occurring to alloy system. Electrical resistivity, thermal conductivity, elastic moduli and the values of microhardness are found to be more sensitive than the internal friction to the phase changes. 

Effect of the surface chemistry on the stability and mechanical properties of the Zirconia-Hydroxyapatite bioceramic

2021 ◽  
Vol 23 ◽  
pp. 100980
Author(s):  
M. Es-saddik ◽  
S. Laasri ◽  
M. Taha ◽  
A. Laghzizil ◽  
A. Guidara ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Chemistry ◽  
The Stability

scholarly journals Studies on the Volumetric Stability and Mechanical Properties of Cement-Fly-Ash-Stabilized Steel Slag

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 495
Author(s):  
Mingkai Zhou ◽  
Xu Cheng ◽  
Xiao Chen
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Steel Slag ◽  
Critical Issue ◽  
Expansion Behavior ◽  
Strength Tests ◽  
Road Materials ◽  
Base Course ◽  
The Stability ◽  
Aggregate Base

The stability of steel-slag road materials remains a critical issue in their utilization as an aggregate base course. In this pursuit, the present study was envisaged to investigate the effects of fly ash on the mechanical properties and expansion behavior of cement-fly-ash-stabilized steel slag. Strength tests and expansion tests of the cement-fly-ash-stabilized steel slag with varying additions of fly ash were carried out. The results indicate that the cement-fly-ash-stabilized steel slag exhibited good mechanical properties. The expansion rate and the number of bulges of the stabilized material reduced with an increase in the addition. When the addition of fly ash was 30–60%, the stabilized material was not damaged due to expansion. Furthermore, the results of X-CT, XRD and SEM-EDS show that fly ash reacted with the expansive component of the steel slag. In addition, the macro structure of the stabilized material was found to be changed by an increase in the concentration of the fly ash, in order to improve the volumetric stability. Our study shows that the cement-fly-ash-stabilized steel slag exhibits good mechanical properties and volumetric stability with reasonable additions of fly ash.

Stability of bounded rapid shear flows of a granular material

1996 ◽  
Vol 308 ◽  
pp. 31-62 ◽  
Author(s):  
Chi-Hwa Wang ◽  
R. Jackson ◽  
S. Sundaresan
Keyword(s):  
Growth Rate ◽  
Stability Analysis ◽  
Granular Material ◽  
Bulk Density ◽  
Particulate Material ◽  
Dominant Mode ◽  
Marginal Stability ◽  
Sheared Layer ◽  
The Stability ◽  
Unusual Type

This paper presents a linear stability analysis of a rapidly sheared layer of granular material confined between two parallel solid plates. The form of the steady base-state solution depends on the nature of the interaction between the material and the bounding plates and three cases are considered, in which the boundaries act as sources or sinks of pseudo-thermal energy, or merely confine the material while leaving the velocity profile linear, as in unbounded shear. The stability analysis is conventional, though complicated, and the results are similar in all cases. For given physical properties of the particles and the bounding plates it is found that the condition of marginal stability depends only on the separation between the plates and the mean bulk density of the particulate material contained between them. The system is stable when the thickness of the layer is sufficiently small, but if the thickness is increased it becomes unstable, and initially the fastest growing mode is analogous to modes of the corresponding unbounded problem. However, with a further increase in thickness a new mode becomes dominant and this is of an unusual type, with no analogue in the case of unbounded shear. The growth rate of this mode passes through a maximum at a certain value of the thickness of the sheared layer, at which point it grows much faster than any mode that could be shared with the unbounded problem. The growth rate of the dominant mode also depends on the bulk density of the material, and is greatest when this is neither very large nor very small.

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