scholarly journals Experimental Study on Compression Deformation and Permeability Characteristics of Grading Broken Gangue under Stress

Processes ◽  
2018 ◽  
Vol 6 (12) ◽  
pp. 257 ◽  
Author(s):  
Yu Zhang ◽  
Wei Zhou ◽  
Ming Li ◽  
Zhanqing Chen
Keyword(s):  
Axial Stress ◽  
Compression Modulus ◽  
Raw Material ◽  
Compression Rate ◽  
Lateral Compression ◽  
Seepage Velocity ◽  
Permeability Characteristics ◽  
Backfill Mining ◽  
Important Test ◽  
Overlying Strata

As the important raw material for backfill mining, broken gangue’s deformation and permeability characteristics directly affect the deformation of the overlying strata above the filling space. In this paper, through lateral compression and pressed seepage tests, the deformation and permeability characteristics of broken gangue as a function of the stress level and grading features were studied. This research indicates that the stress of broken gangue increases exponentially with an increase in strain, and the compression modulus and compression rate present a positive correlation. The samples with discontinuous grading are more difficult to compress than the continuous grading samples, and the discontinuous grading samples are tighter in accordance with the increase in compression rate. At the same time, the change range of the seepage velocity and permeability of the broken gangue decreases. Positive correction between the grading index of the broken gangue and the effect of reducing the permeability of samples is more obvious under axial compression, and less axial stress is needed to achieve the same permeability level for discontinuous grading. This paper can provide an important test basis for the design of grading parameters and the prediction of filling effects of broken gangue on backfill mining.

Ultimate Elastic Wall Stress (UEWS) Test under Biaxial Loading for Glass-Fibre Reinforced Epoxy (GRE) Pipes

2014 ◽  
Vol 974 ◽  
pp. 188-194 ◽  
Author(s):  
Tarak A. Assaleh ◽  
Lutfeya A. Almagguz
Keyword(s):  
Biaxial Loading ◽  
Pipe Wall ◽  
Axial Stress ◽  
Wall Stress ◽  
Current Method ◽  
Raw Material ◽  
Attractive Alternative ◽  
Filament Wound ◽  
Elastic Wall ◽  
Filament Wound Composite

This paper presents the results of an experimental investigation into the Ultimate Elastic Wall Stress (UEWS) of ±55° filament wound composite pipes. The UEWS test appears to provide an attractive alternative to the current method, and has proved to be one of the most effective in term of accuracy and speed. Moreover, it has been found to be sensitive to changes in key manufacturing and raw material parameters. The pipes were subjected to biaxial loading, which was achieved by combinations of hoop and axial stress. Loads were applied as groups of cycles which, were gradually increased until the UEWS had been determined. Various ratios of hoop to axial stress were applied to the pipes, ranging from pure axial to pure hoop loading at room temperature and at 65°C. These ratios were investigated by applying different pressures in both the main and small chambers built inside the pipe, and therefore it was unnecessary to add any external loads to the pipe wall. Tests were also conducted to observe leakage through the pipe wall. The main failure mode observed was weepage through the pipe wall, which was due to intensive matrix microcracking. The results from the UEWS tests are presented in the form of failure envelopes showing the effects of testing at an elevated temperature. Finally, degradation in the elastic properties of the pipe wall is also discussed and plotted against wall stress.

scholarly journals Physical Modeling of the Controlled Water-Flowing Fracture Development during Short-Wall Block Backfill Mining

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Yun Zhang ◽  
Yongzi Liu ◽  
Xingping Lai ◽  
Jianming Gao
Keyword(s):  
Coal Pillar ◽  
Similarity Criterion ◽  
Test Results ◽  
Control Effect ◽  
Physical Similarity ◽  
Wall Block ◽  
Fracture Development ◽  
Backfill Mining ◽  
Backfill Materials ◽  
Overlying Strata

Abstract Short-wall block backfill mining (SBBM) technology is an effective method to solve the environmental problems in the mining process. Based on the technical characteristics of SBBM technology and the physical similarity criterion, the physical similarity models for comparing the control effects of water-flowing fracture (WFF) development using short-wall block cave mining (SBCM) and SBBM were established, and the deformation and the WFF development of overlying strata above gob were monitored. The test results determined that the composite materials of 5 mm thick pearl sponge+5 mm thick sponge+10 mm thick paper+6 mm thick board were adopted as the similar backfill materials by comparing the stress-strain curves between the similar backfill materials and the original gangue sample. When the backfilling body was filled into the gob, it would be the permanent bearing body, which bore the load of the overlying strata accompanied with the protective coal pillar. At the same time, the backfilling body also filled the collapse space of overlying strata, which was equivalent to reduce the mining height, and effectively reduced the subsidence and failure height of the overlying strata. Compared with SBCM, the test results showed that the maximum vertical deformation, the height of water-flowing fractured zone, and activity range of overlying strata using SBBM were reduced by 91.4%, 82.5%, and 64.9%, respectively. SBBM had a significant control effect on strata damage and WFF development, which could realize the purpose of water resource protection in coal mines.

Research on Influencing Factors of Wood Residual Fiber Foaming Cushion Material

2012 ◽  
Vol 511 ◽  
pp. 46-50
Author(s):  
Bin Cao ◽  
Sheng Ling Xiao ◽  
Xiao Qing Pan
Keyword(s):  
Mechanical Property ◽  
Surface Quality ◽  
Influencing Factors ◽  
Compression Strength ◽  
Wood Fiber ◽  
Compression Modulus ◽  
Hot Compression ◽  
Raw Material ◽  
Single Factor ◽  
Foaming Agent

A wood residual fiber foaming cushion material was prepared by using gathered wood fiber as main raw material, starch/PVA adhesive as matrix, adding a certain amount of foaming agent and related additives, hot compression molding to shape up. This paper makes an investigation of single factor on the product’s surface quality and related mechanical property. Results show that with the amount of wood residual fiber increases, the rebound resilience of the product first increases then decreases. The density decreases along with the amount of foaming agent increases. The compression strength and compression modulus of the product increases along with the amount of wood residual fiber increases, it decreases along with the amount of foaming agent increases.

Evaluation of Stress-Controlled Permeability of Coal Fractures - A Laboratory Study

2013 ◽  
Vol 734-737 ◽  
pp. 703-708
Author(s):  
Yi Dong Cai ◽  
Da Meng Liu ◽  
Yan Bin Yao ◽  
Bai Ren Zhang ◽  
Jun Qian Li ◽  
...  
Keyword(s):  
Elastic Deformation ◽  
Axial Stress ◽  
Fractal Dimensions ◽  
Confining Pressure ◽  
Control Factor ◽  
Type I ◽  
Permeability Characteristics ◽  
Linear Elastic ◽  
Variable Permeability ◽  
Nonlinear Elastic

Experiments on coal permeability with saturated water under tri-axial stress were conducted. The relationship between stress and permeability under tri-axial stress was analyzed on the rock mechanical experimental rig (GAW-2000). After the experiments on permeability, the fracture characteristics were researched by X-ray computerized tomography, which shows that the bituminous coal normally has high fractal dimensions (generally over 1.8) and wide aperture. The results for permeability reveal that bituminous coals always have variable permeability characteristics under incremental axial stress due to its inherent fracture features. It can be divided into two types: type I, at the linear and nonlinear elastic deformation and peak stage, the permeability keeps rising, which is represented by FYGY8 #. The main control factor of permeability should be related to coal microfractures and coal compositions. Type II, which is represented by sample YCLZ2#, in the initial linear elastic stage, there is a decrease trend in the permeability performance, and then permeability gradually rise when it comes into the stage of nonlinear elastic deformation. The permeability will keep go down after coal becomes soften under the action of confining pressure, compaction.

scholarly journals Non-linear elastic behavior of carbon fibres of different structural and mechanical characteristic

2007 ◽  
Vol 72 (5) ◽  
pp. 513-521 ◽  
Author(s):  
Isidor Djordjevic ◽  
Daniela Sekulic ◽  
Momcilo Stevanovic
Keyword(s):  
Tensile Strain ◽  
Axial Stress ◽  
Tensile Modulus ◽  
Compression Modulus ◽  
Interlayer Spacing ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Carbon Fibres ◽  
Single Filament ◽  
Breaking Strain

Five types of polyacrylonitrile, PAN, based carbon fibres, differing in modulus, breaking strain and in crystallite orientation, have been studied. Non-Hookean behavior was investigated by computing the tangent tensile and compression moduli as a function of strain, from the axial stress-strain response obtained in standard tensile, compression, as well as in modified flexural tests of unidirectional carbon/ epoxy composites. The dependences of the tensile modulus on tensile strain of the carbon fibres were extracted from data obtained in single-filament tensile tests. Analytical expressions for the tensile modulus-tensile strain and compression modulus-compression strain dependences in the performed test were deduced. The structural characterization of the carbon fibres was performed by X-ray diffraction on bundle of parallel fibres. The interlayer spacing d 002 and the apparent lateral dimension of the crystallites L c were deduced by processing the 002 diffraction profiles. The established modulus-strain dependences were correlated with the fibre characteristics (breaking strain and mean modulus values), as well as with the characteristic of the 002 difraction profile and the d 002 and L c values.

scholarly journals Experimental study on permeability characteristics of gas-containing raw coal under different stress conditions

2018 ◽  
Vol 5 (7) ◽  
pp. 180558 ◽  
Author(s):  
Dongming Zhang ◽  
Yushun Yang ◽  
Hao Wang ◽  
Xin Bai ◽  
Chen Ye ◽  
...  
Keyword(s):  
Flow Rate ◽  
Coal Sample ◽  
Axial Stress ◽  
Axial Strain ◽  
Confining Pressure ◽  
Gas Pressure ◽  
Permeability Characteristics ◽  
Loading And Unloading ◽  
Unloading Confining Pressure ◽  
Function Relation

The present experimental study on permeability characteristics for raw coal under different stress states is implemented by applying the triaxial self-made ‘THM coupled with servo-controlled seepage apparatus for gas-containing coal’; the result indicates that the flow rate of gas in the coal sample gradually decreases with the nonlinear loading of axial pressure and increases with the nonlinear unloading of axial stress and confining pressure. The flow rate, axial stress and confining pressure curves all satisfy the negative exponential function relation. When the sample reaches the peak intensity, the sample will be destroyed and the stress will drop rapidly; then the flow rate of the sample will increase rapidly. At this stage, the flow rate and axial strain show an oblique ‘v' pattern. The flow rate of the coal sample increases nonlinearly with the increase of gas pressure; the relation curve between flow rate and gas pressure satisfies the power function relation. Under the same confining pressure and gas pressure conditions, the larger the axial stress, the smaller the flow rate of the coal sample. Under the same axial stress and gas pressure conditions, the flow rate of the coal sample will first decrease, but then increase as the confining pressure decreases. During the post-peak loading and unloading process, the flow rate of the coal sample will decrease with the loading of confining pressure but increase with the unloading of confining pressure, and there will be an increase in wave shape with the increase in axial strain. The flow rate of each loading and unloading confining pressure is higher than that of the previous loading and unloading confining pressure. At the post-peak stage, the relation curve between the flow rate of the coal sample and the confining pressure satisfies the power function relation in the process of loading and unloading confining pressure.

scholarly journals ALTERNATIVE METHOD FOR QUALIFICATIONS OF GLASS FIBRE REINFORCED EPOXY PIPES (GRE)

2019 ◽  
Vol 2 (2) ◽  
pp. 73-81
Author(s):  
Tarak Assaleh ◽  
Siddig Dabbashi ◽  
Asya A. Gabbasa
Keyword(s):  
Biaxial Loading ◽  
Axial Stress ◽  
Wall Stress ◽  
Raw Material ◽  
Attractive Alternative ◽  
Hydrostatic Loading ◽  
Biaxial Load ◽  
Pressure Tests ◽  
Glass Fibre Reinforced

This paper discusses the Ultimate Elastic Wall Stress (UEWS) test for GRE pipes under pure hydrostatic loading. UEWS appears to provide an attractive alternative to the currently used procedure laid down in ISO 14692, which involves an expensive series of long term constant pressure tests, as described in ASTM 2992, running for a period in excess of 10,000 hours. The pipes were subjected to biaxial loading, which was attained by combinations of hoop and axial stress. Loads were applied as groups of cycles which, were gradually increased until the UEWS had been determined. UEWS test has proved to be one of the most effective in terms of accuracy and speed. Moreover, it has been found to be sensitive to changes in key manufacturing and raw material parameters. Modelling results are also showed a harmonic approach and accepted to that obtained experimentally. This encourages to apply the proposed modelling for further biaxial load ratios.

scholarly journals Study on the Permeability Change Characteristic of Gas-Bearing Coal under Cyclic Loading and Unloading Path

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Fakai Wang ◽  
Xuelong Li ◽  
Bo Cui ◽  
Jian Hao ◽  
Peng Chen
Keyword(s):  
Cyclic Loading ◽  
Radial Stress ◽  
Axial Stress ◽  
Cumulative Damage ◽  
Factors Affecting ◽  
Permeability Characteristics ◽  
Cyclic Loading And Unloading ◽  
Damage Rate ◽  
Loading And Unloading ◽  
Gas Bearing

Using the self-developed three-axis servo fluid-solid coupling system with gas-solid coupling of gas-bearing coal, the variation law of the permeability of gas coal under the stress cycle loading and unloading path was studied. The qualitative and quantitative relationships between permeability, axial force, and radial stress of gas-bearing coals were established, and the variation law of permeability of gas-bearing coals was discussed. The results show that (1) different cyclic loading and unloading stress paths correspond to the permeability characteristics of different gas-bearing coals. (2) Permeability of gas-bearing coal decreases with the increase of axial stress and radial stress, and it has a logarithmic function with axial stress and radial stress. This shows that axial stress and radial stress are important factors affecting the permeability characteristics of gas-bearing coal. (3) Under the same stress loading and unloading conditions, the axial stress is less than radial stress on the permeability of gas-bearing coal. In the cyclic loading and unloading axial stress process, the permeability of the gas-bearing coal varies by a smaller extent than the cyclically unloaded confining force. (4) The cumulative damage rate of gas-bearing coal under axial stress gradually increases with the increase of the number of cycles of loading and unloading, and the rate of the cumulative damage rate of permeability is less than the corresponding rate of radial stress.

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