scholarly journals In Situ Stress Effects on Smooth Blasting: Model Test and Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Renshu Yang ◽  
Shizheng Fang ◽  
Aiyun Yang ◽  
Huanzhen Xie ◽  
Liyun Yang
Keyword(s):  
Strain Rate ◽  
Confining Pressure ◽  
Equivalent Strain ◽  
In Situ Stress ◽  
Image Correlation ◽  
Propagation Mechanism ◽  
Equivalent Strain Rate ◽  
Ground Stress ◽  
Smooth Blasting

Most of the roadway excavation is completed by the drilling and blasting method. With the increase of buried depth, the existence of ground stress will generate a significant impact on the rock blasting, especially on the smooth blasting. In this study, self-made homogeneous similar materials and digital image correlation methods were used to determine influence of ground stress on the smooth blasting under uniform explosive charge parameters and various in situ stress conditions. The results show that the crack outline after blasting changes from zigzag to straight in shape, and multifractal calculation results of the rupture section between blastholes show that the fracture surface becomes flatter as ground stress increases, which is conducive to roadway formation. The strain and equivalent strain rate obviously decrease as the distance between the blasthole and measuring points increases. The same trend occurs as the confining pressure goes up. Meanwhile, a postexplosion acoustic wave test indicates that confining pressure inhibits damage of the retained rock, which is consistent with strain and equivalent strain rate results. Finally, we discussed the crack propagation mechanism of rock in smooth blasting.

scholarly journals Effect of Stress and Moisture Content on Permeability of Gas-Saturated Raw Coal

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Junhui Wang ◽  
Zhijun Wan ◽  
Yi Wang ◽  
Zhixiang Liu ◽  
Sifei Liu ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coalbed Methane ◽  
Confining Pressure ◽  
Porous Matrix ◽  
In Situ Stress ◽  
Permeability Evolution ◽  
Test Range ◽  
Moisture Contents ◽  
Volumetric Stress

Hydraulic fracturing and premining gas drainage are important to safe mining and coalbed methane extraction. These technical processes cause the redistribution of in-situ stress and the regional variation of moisture contents within the affected zone. Therefore, we investigated the coupled effect of variable stresses (from 9 MPa to 27 MPa) and moisture contents (from 0.22% to 4.00%) on the permeability evolution of gas-saturated raw coal. The results show that (1) the relationship between the mean effective stress and the permeability can be described by a power function according to the permeability evolution model of the porous matrix established in this study. Besides, the influence mechanisms of moisture on fitting coefficients in the function were analyzed. (2) The permeability decreases with the increase of in-situ stress (e.g., confining pressure or volumetric stress) in a negative exponential manner. (3) The curves of permeability variations with moisture content are not always linear, and the permeability is more sensitive to the moisture content than the volumetric stress in the test range. Moreover, the sensitivity of permeability varies in different regions. These results would be beneficial for permeability prediction and surface well parameters design.

scholarly journals An An Analysis of Strain Rate Distribution Using Streamline Model and A Quick Stop Device in Metal Cutting

2019 ◽  
Vol 22 (2) ◽  
pp. 136-142
Author(s):  
Osama Ali Kadhim ◽  
Fathi A. Alshamma
Keyword(s):  
Strain Rate ◽  
Chip Formation ◽  
Metal Cutting ◽  
Equivalent Strain ◽  
Element Analysis ◽  
Rate Distribution ◽  
Equivalent Strain Rate ◽  
Cumulative Plastic Strain ◽  
Cutting Speeds ◽  
Strain Rate Distribution

In this paper, a quick stop device technique and the streamline model were employed to study the chip formation in metal cutting. The behavior of chip deformation at the primary shear zone was described by this model. Orthogonal test of turning process over a workpiece of the 6061-T6 aluminum alloy at different cutting speeds was carried out. The results of the equivalent strain rate and cumulative plastic strain were used to describe the complexity of chip formation. Finite element analysis by ABAQUS/explicit package was also employed to verify the streamline model. Some behavior of formation and strain rate distribution differs from the experimental results, but the overall trend and maximum results are approximately close. In addition, the quick stop device technique is described in detail. Which could be used in other kinds of studies, such as the metallurgical observation.

Modeling of Diffuse Damage Near Micro Cracks in Human Cortical Bone

2012 ◽  
Author(s):  
E. Budyn ◽  
T. Hoc
Keyword(s):  
Cortical Bone ◽  
Strain Energy ◽  
Numerical Approach ◽  
In Situ Stress ◽  
Image Correlation ◽  
Bone Morphology ◽  
Micro Cracks ◽  
Daily Exercise ◽  
In Situ Stress Field

Haversian cortical bone is a mineralised tissue that undergoes micro damage under daily exercise. Micro damage can either be identiable by light microscopy as microcracks or be more diffuse and difficult to visualise. Bone is maintained by mechano-sensitive cells called osteocytes located throughout the tissue. However the local mechanical stimulations on the cells are not precisely quantied. A dual experimental and numerical approach is presented to measure the in situ stress field produced by microcracks in human bone. Using the strain energy balance, the stress eld is reconstructed in the vicinity of quasi-static microcracks that are advancing in the explicit bone morphology captured by digital image correlation. The stress eld reveals the presence of diffuse damage near microcracks in agreement with experimental observations in the literature.

The Research and Optimization of a 6061 Aluminum Rectangular Tube Extrusion Using Porthole Dies According to the Parameter of Split Ratio

2012 ◽  
Vol 268-270 ◽  
pp. 391-395
Author(s):  
Shu Mei Lou ◽  
Guo Liang Xing ◽  
Sheng Xue Qin ◽  
Lin Jing Xiao
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Strain Rate ◽  
Equivalent Strain ◽  
Tube Extrusion ◽  
Split Ratio ◽  
Die Structure ◽  
Rectangular Tube ◽  
Equivalent Strain Rate ◽  
Deform 3D

Extrusions of a 6061 aluminum rectangular tube using porthole dies with three assigned different split ratios were simulated by the software DEFORM-3D based on Finite element method. The distributions of stress, equivalent strain rate, temperature, velocity of the deformation materials and the mold stress during the three extrusion processes were obtained, respectively. By analyzing the distributions of those fields, the most reasonable split ratio is selected and then the die structure is modified.

scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

AbstractDeformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

scholarly journals Tools for examining subglacial bed deformation

1992 ◽  
Vol 38 (130) ◽  
pp. 388-396 ◽  
Author(s):  
Erik Blake ◽  
Garry K. C. Clarke ◽  
Marc C. Gérin
Keyword(s):  
Strain Rate ◽  
In Situ Stress ◽  
Yukon Territory ◽  
Strain Rates ◽  
Strain Measurements ◽  
Bed Deformation ◽  
Instantaneous Strain ◽  
Order Of Magnitude

Abstract Deformation beneath soft-bedded glaciers may be a physical mechanism that contributes to flow instabilities such as surging. If the role of bed deformation is to be understood, a rheological description is required, but the development of a rheology is hampered by a lack of in situ stress and strain measurements. In this paper, we describe four techniques for measuring subglacial strain. Three of these give continuous strain measurements, a capability that permits calculation of instantaneous strain rates and allows comparison of strain data with other time series. To demonstrate the practicability of the techniques, sample results from three summers of experimentation beneath Trapridge Glacier. Yukon Territory, are presented. The data show that subglacial strain rate can vary in amplitude and polarity on an hourly time-scale,and that the instantaneous strain rate can exceed the mean strain rale by an order of magnitude. Observed negative strain rates suggest extrusive flow within basal sediments.

scholarly journals Effect of wet-dry cycles on disintegration characteristics of clay-bearing sandstone with UF cracks

2020 ◽  
Author(s):  
Yu Wang ◽  
Qingning Qiao ◽  
Jianlin Li
Keyword(s):  
Confining Pressure ◽  
In Situ Stress ◽  
Three Gorges Reservoir Area ◽  
Test Results ◽  
Rock Samples ◽  
Pressure Experiment ◽  
Size Uniformity ◽  
In Situ Stress Field ◽  
Unloading Confining Pressure

UF cracks in rock masses commonly occur due to the unloading effect, which constantly happens after the variation of in-situ stress field or rock excavation. When undergoing periodic water fluctuation, rock mass with UF cracks is vulnerable to deterioration or even disintegration, especially for clay-bearing sandstone. To study the effect of changes in moisture on rock samples with UF cracks, clay-bearing sandstone from the Triassic Badong group in the Three Gorges Reservoir Area were chosen and investigated. The rock samples with UF cracks are obtained by conducting triaxial unloading confining pressure experiment. The effect of wet-dry cycles on the morphology properties and microstructure of the UF surface was investigated. The characteristics of particle-size uniformity from the sieve test were obtained by the calculation of RMS of particle contents. The test results show that UF cracks widen significantly and the disintegrated mass increases rapidly in the first three wet-dry cycles, while the fractal dimension of UF surface decreases sharply, but afterwards the disintegrated mass changes gently and the UF surface tends to be flat and smooth. Then, the RMS calculation of particle contents quantitatively evaluate the clay-bearing sandstone’s disintegration properties, which indicate the particle uniformity plays a key role on its disintegration mechanism. During wet-dry cycles, the tested samples tend to disintegrate more rapidly and entirely with the decrease of particle uniformity.

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