scholarly journals Mechanical Properties and Control Rockburst Mechanism of Coal and Rock Mass with Bursting Liability in Deep Mining

2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Ming-tao Gao ◽  
Zhen-qi Song ◽  
Hui-qiang Duan ◽  
Heng-qi Xin ◽  
Jian-quan Tang
Keyword(s):  
Mechanical Properties ◽  
Large Diameter ◽  
Confining Pressure ◽  
Test System ◽  
Peak Strength ◽  
Dissipated Energy ◽  
Engineering Practice ◽  
Working Face ◽  
And Control

In order to study the mechanism of the dynamic disaster of rockburst in a deep coal mine and the prevention and control measures of weakening shock, the MTS815.03 servocontrolled rock mechanics test system is used to test the coal, rock, and combined specimens with the buried depth of nearly 1200 m in Xinwen Mining Area. And their mechanical properties, energy evolution, and bursting properties are studied and analyzed. The rationality of the test results is also verified by the in-situ engineering practice. The key conclusions are as follows: (1) There is a relation between the ratio of elastic modulus Ee before peak strength to descending modulus Ed after peak strength and the bursting properties. For the fractured coal, the descending modulus Ed is relatively small, and the Ee/Ed is relatively large and presents progressive ductile failure with low probability and risk of rockburst. For the less fractured rock, the descending modulus Ed is relatively large, and the Ee/Ed is relatively small and presents brittle failure, which is very similar to the characteristics of rockburst. (2) For the same type of rock, with the increase of confining pressure, the Ee/Ed gradually increases, indicating the reduction of rockburst strength. Therefore, the greater the support strength provided to the surrounding rock surface of the roadway, the smaller the failure degree of rockburst. (3) With the increase of confining pressure, after peak strength, the elastic energy of coal specimens decreases slowly, and the dissipated energy increases slowly, indicating that the increase of confining pressure can effectively limit the energy dissipation and release after coal specimen failure. So, in the in-situ engineering practice, it is an important measure to improve the surface restraint and support strength of the coal roadway for reducing the occurrence intensity and probability of rockburst. (4) The combined measures of “the mining of double liberating seam + the implementation of large-diameter pressure relief borehole in advance of working face” is the very effective way to eliminate the rockburst accidents of working face in a protected coal seam and has an important guiding significance for the safe mining of rockburst mine.

Study on Shear Strength of Artificial Methane Hydrate

2010 ◽  
Author(s):  
Feng Yu ◽  
Yongchen Song ◽  
Weiguo Liu ◽  
Yanghui Li ◽  
Jiafei Zhao
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Shear Strength ◽  
Strain Rate ◽  
Methane Hydrate ◽  
Confining Pressure ◽  
Test System ◽  
Secant Modulus ◽  
Shear Tests ◽  
Hydrate Reservoir

The production of methane from hydrate reservoir may induce deformation of the hydrate-bearing strata. The research on mechanical properties of methane hydrate and establishing an efficient methane exploitation technology appear very important. In this paper, a low-temperature high-pressure triaxial test system including pressure crystal device (sample preparation system) was developed. A series of triaxial shear tests were carried out on artificial methane hydrate samples. The mechanical behavior was analyzed. The preliminary results show that the shear strength of methane hydrate increases with the increase of confining pressure and strain rate. While it increases with the decrease of temperature. Moreover, the secant modulus increases with the enhancement of strain rate and the decrease of confining pressure.

scholarly journals Crack propagation characteristics and mechanism of energy evolution in intermittent externally fissured sandstone

2020 ◽  
Author(s):  
Hui Yu ◽  
Shaowei Liu ◽  
Housheng Jia ◽  
Huaichang Zheng ◽  
Zhihe Liu
Keyword(s):  
Confining Pressure ◽  
Crack Development ◽  
Peak Strength ◽  
Lateral Strain ◽  
Dissipated Energy ◽  
Peak Strain ◽  
Rock Bridge ◽  
Damage And Fracture ◽  
Laboratory Test Results ◽  
Fissured Rock

Abstract Geostress environment and fracture distribution both exert important influences on the mechanical properties and failure modes of fissured rock masses. Laboratory test results are presented here to simulate particle flow code (PFC) in externally double-fissured sandstone samples. Mechanical responses of confining pressure and rock bridge angle on stress-strain curves as well as macroscopic damage and fracture propagation in these samples were studied in order to elucidate energy dissipation mechanisms. The results of this analysis show that fissured sandstone peak strength and elastic modulus as well as peak axial and lateral strain increase significantly as rock bridge angle decreases while peak strength increases slightly in concert with confining pressure. Rock bridge angle exerts an important influence on macro fracturing patterns; when β = 0°, wing cracks from two pre-existing external fissures propagate in opposite directions, but when β = 60°, the inner tips of two external fissures become directly connected. The evolution of specimen fracturing passes through four main stages, elastic compression deformation, stable crack development, unstable crack development, and post-peak accelerated crack development. Internal contact forces reach maximum values at the peak stress point, while cracks are mainly tensile and shear examples are mostly distributed at orientations between 80° and 100°. Shear cracks are mainly generated along the direction of main stress, σ 1 , while pre-peak dissipated energy is small, and increases rapidly at the post-peak. As rock bridge angle decreases, peak strain and boundary energies both increase significantly. Data show that energy and rock bridge angle are approximately linearly positively correlated.

scholarly journals MECHANICAL PROPERTIES OF SANDSTONE SUBJECTED TO COUPLING OF TEMPERATURE–SEEPAGE–STRESS

10.6036/10055 ◽  
2021 ◽  
Vol 96 (3) ◽  
pp. 309-315
Author(s):  
Lijie Long ◽  
Dongyan Liu ◽  
Dong Wang ◽  
Jin Li
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Rock Mass ◽  
Elastic Modulus ◽  
Plastic Zone ◽  
Residual Strength ◽  
Confining Pressure ◽  
Peak Strength ◽  
Hydraulic Pressure ◽  
Stress Strain

ABSTRACT: The deformation and fracture of rock mass in deep rock mass engineering are affected by the coupling of temperature, seepage, and stress. A test and a calculation model for sandstone under thermal–hydrological–mechanical (THM) coupling were proposed to reveal the mechanical properties of sandstone. The law of coupling for mechanical indicators of sandstone was established by laboratory tests and numerical simulations. The permeability, peak strength, peak strain, residual strength, elastic modulus, plastic deformation area, and stress–strain cloud diagram were analyzed by the steady state seepage method and THM coupling principle, and the accuracy of the model was verified. Results demonstrate that: (1) As the temperature rises and the peak deformation increases, the sample slowly drops to the residual strength level after the peak stress. (2) The main factor that affects peak strength is confining pressure. In the temperature range of 25 °C–50 °C, the maximum peak strength and peak deformation are increased by heating, and the increases in confining pressure and temperature reduce the reduction coefficient of the residual strength. Moreover, the elastic modulus increases with the increase in confining pressure, but it shows a downward trend when the temperature increases. (3) The plastic deformation zone and stress–strain cloud diagram indicated that when the temperature and osmotic pressure increase, the specimen enters the plastic zone earlier, the effective plastic zone increases, the stress increases, and the deformation is intensified. The proposed method provides a certain reference for the permeability and stability evaluation of rock mass under the conditions of “three-high” (high confining pressure, high hydraulic pressure, and high stress) engineering. Keywords: temperature–seepage–stress coupling, sandstone, mechanical properties

Experimental Study on the Anisotropy of Layered Rock Mass under Triaxial Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Long Cheng ◽  
Hui Wang ◽  
Xu Chang ◽  
Yewei Chen ◽  
Feilu Xu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Confining Pressure ◽  
Peak Strength ◽  
Rock Composition ◽  
Rock Formations ◽  
Geological Conditions ◽  
Anisotropic Mechanical Properties ◽  
Confining Pressures ◽  
Dip Angle ◽  
Rock Specimens

Weak and hard inhomogeneous rock formations are typically encountered during tunnel excavations. The physical and mechanical properties and geological conditions of these rock formations vary significantly; thus, it is crucial to investigate the mechanical characteristics of deep bedded composite rock formations. Three-dimensional (3D) scanning and 3D printing were used to prepare composite rock specimens to simulate natural rock laminae. Triaxial compression tests were conducted to determine the influence of the bedding angle, rock composition, and confining pressure on the mechanical properties of the composite rock specimens. The anisotropic strength characteristics and the damage patterns of the composite rock specimens were analyzed under different confining pressures, and the failure mechanism during triaxial loading was revealed. The results show that the damage of the composite rock specimens with a bedding structure depends on the bedding dip angle and the rock formation. The stress-strain curves and peak strengths of the composite rock specimens have anisotropic characteristics corresponding to their failure modes. As the bedding dip angle increases, the peak strength of the three groups of specimens first decreases and then increases under different confining pressure levels. The compressive strength has a nonlinear relationship with the confining pressure, and the difference between the compressive strengths of specimens with different inclination angles decreases as the confining pressure increases. The Hoek–Brown strength criterion is a good predictor of the nonlinear increase in peak strength of the composite rock specimens under different confining pressures. The specimen with a β  = 60°dip angle shows the most significant increase in the strength difference with increasing confining pressure. The results can be used as a reference for testing and analyzing the anisotropic mechanical properties of bedded rock masses.

scholarly journals Study on the Mechanical Properties of Fly-Ash-Based Light-Weighted Porous Geopolymer and Its Utilization in Roof-Adaptive End Filling Technology

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4450
Author(s):  
Luchang Xiong ◽  
Bowen Fan ◽  
Zhijun Wan ◽  
Zhaoyang Zhang ◽  
Yuan Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Porous Structure ◽  
High Efficiency ◽  
Influence Factor ◽  
Structure Model ◽  
Plastic Yielding ◽  
Working Face ◽  
Secondary Air

This paper aims to study the porous structure and the mechanical properties of fly-ash-based light-weighted porous geopolymer (FBLPG), exploring the feasibility of using it in roof-adaptive end filling technology based on its in-situ foaming characteristics and plastic yielding performance. A porous structure model of FBLPG during both the slurry and solid period was established to study their influence factor. In addition, this study also built a planar structure model in the shape of a honeycomb with bore walls, proving that the bore walls possess the characteristics of isotropic force. FBLPG shows a peculiar plastic yielding performance in the experiment where its stress stays stable with the gradual increase of the deformation, which can guarantee the stability of a filling body under the cycled load from the roof. At the same time, the in-situ foaming process combined with the unique filling technique can make the FBLPG filling body fully in contact with the irregular roof. This roof-adaptive end filling technology makes it a successful application in plugging the 1305 working face, which avoids problems of the low tight-connection ratio and secondary air-leakage channel resulted from the traditional filling technology, effectively improving coal production in terms of safety and high efficiency.

scholarly journals Constitutive Model of N15 Propellant considering the Confining Pressure Effect

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Tianpeng Li ◽  
Junli Han ◽  
Shixin Wang ◽  
Yong He ◽  
Xiong Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Pressure Effect ◽  
Rupture Strength ◽  
Confining Pressure ◽  
Test System ◽  
Model Parameters ◽  
Initial Modulus ◽  
Confining Pressures ◽  
Confining Pressure Effect

To describe the effect of confining pressure on the mechanical responses of N15 propellant, a constitutive model considering the confining pressure effect was first established for N15 propellant based on the elastic-viscoelastic correspondence principle. Then, the mechanical properties of N15 solid propellant under different confining pressures were obtained using confining pressure test system, and the obtained results indicate that the initial modulus of propellant did not change with confining pressure, but the maximum tensile strength, rupture strength, the maximum elongation, and elongation at break increased with increasing confining pressure. In conjunction with propellants’ mesoscopic structure and cross-section analysis, the mechanical mechanism of confining pressure effect on propellant was initially disclosed. Due to confining pressure, the particle dewetting inside the propellant was reduced, the hole propagation was delayed, and crack extension inhibited germination, proving that confining pressure has a strengthening impact on the propellant. Finally, assuming that the model parameters were dependent on pressure, the model parameters acquisition and validation were conducted. The results demonstrated that constitutive model can describe confining pressure influence on the mechanical properties of N15 propellant accurately.

scholarly journals Effect of Radiation on Topopah Spring Tuff Mechanical Properties

1996 ◽  
Vol 465 ◽  
Author(s):  
P. A. Berge ◽  
S. C. Blair
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Peak Strength ◽  
Test Results ◽  
Welded Tuff ◽  
Discernible Effect ◽  
And Control ◽  
Compressive Tests ◽  
Topopah Spring Tuff

ABSTRACTThe effect of radiation on the mechanical properties of Topopah Spring tuff was investigated by performing uniaxial compressive tests on irradiated and control samples of the tuff from the potential repository horizon at Yucca Mountain. Test results are presented, including stress-strain curves and peak strength and Young's modulus values. The results from this preliminary study show that for uncracked samples of Topopah Spring tuff, exposure to gamma radiation had no discernible effect on the unconfined compressive (peak) strength or the Young's modulus. However, results for samples that contained partially healed subvertical cracks indicate that exposure to radiation may reduce the strength and Young's modulus significantly. This is attributed to weakening of the cementing materials in the cracks and fractures of the samples that were irradiated. These results are preliminary, and additional studies are warranted to evaluate whether radiation weakens cementing materials in welded tuff.

scholarly journals Mechanical Behavior and Damage Evolution for Granite Subjected to Cyclic Loading

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Zhiliang Wang ◽  
Jikang Yao ◽  
Nuocheng Tian ◽  
Jingbin Zheng ◽  
Peng Gao
Keyword(s):  
Cyclic Loading ◽  
Mechanical Behavior ◽  
Damage Evolution ◽  
Confining Pressure ◽  
Test System ◽  
Triaxial Tests ◽  
Dissipated Energy ◽  
Granite Sample ◽  
Cycle Number ◽  
Four Levels

This paper focuses on the mechanical behavior and damage evolution of Huashan granite subjected to cyclic loading. Four levels of confining pressure (0, 15, 25, and 35 MPa) were applied during cyclic axial loading by using a Rock Test System (MTS815) along with an acoustic emission (AE) monitoring device. Experimental results indicate that the number of AE activities is higher under cyclic triaxial loading compared to that under cyclic uniaxial loading. The measured stress-strain curves of both uniaxial and triaxial tests under cyclic loading are concave-up, but the degree of concavity is mild for the latter. As the cycle number rises, elastic modulus of the granite sample under different confining pressures increases. The slope of the peak strength versus confining pressure plot for the cyclic loading is larger than that for the monotonic loading. Besides, it is found that the dissipated energy increases with the increase of cyclic stress, but it hardly increases in proportion with the confining pressure. The damage parameters defined in terms of the plastic strain can be extended for the whole cyclic loading process, and they agree well with the energy-based damage parameters.

Analysis between Water Contain and Lithology

2015 ◽  
Vol 744-746 ◽  
pp. 422-425
Author(s):  
Qiu Mei Zhang ◽  
Jin Tao Tang ◽  
Hao Ma
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Water Content ◽  
Prevention And Control ◽  
Great Influence ◽  
Test System ◽  
Control Measures ◽  
Prevention And Control Measures ◽  
Rock Mechanical Properties ◽  
And Control

Water content has a great influence on the rock mechanics properties. Four kinds of rock samples have been tested in the MTS Electro hydraulic Tri-axial Servo Test System. The result shows that with the increase of water content, the rock uniaxial compressive strength and elastic modulus value are declining. We get the fitting equation between water content and rock mechanical properties with four kind of rocks, provide a new basis for slope stability analysis and landslide prevention and control measures.

Dislocation fine structure and mechanical properties of intermetallic alloys

1989 ◽  
Vol 47 ◽  
pp. 300-301
Author(s):  
P. Veyssière
Keyword(s):  
Mechanical Properties ◽  
Fine Structure ◽  
Ceramic Materials ◽  
General Interest ◽  
Intermetallic Alloys ◽  
Bulk Materials ◽  
Strain Gradients ◽  
Weak Beam ◽  
And Control

Weak-beam (WB) TEM was introduced in the late sixties and flourished during the following decade. It revealed the most powerful all-materials technique for the imaging of very localized strain gradients as for instance in dislocation studies. Although some of its first achievements dealt with the resolution of subdissociation in ordered materials, WB happened to be mostly utilized to answer questions raised along 25 years of active speculation on dissociation in fcc, bcc and hcp metals and alloys; in addition, it helped exploring dislocation properties in ceramic materials (oxides, semiconductors, carbides). With the loss of general interest in core-related dislocation phenomena, the WB technique then became much less popular (excepted for semiconductors) until the new impulse given by the materials community in the field of intermetallic alloys; this effort is the object of the present review. In the meantime, the ultimate resolution obtainable from WB conditions got constantly improved: a separation between dislocation images lesser than 1.5nm is now accessible on modem microscopes. Due to the failure of the column approximation, new precautions then have to be taken at analyzing images (especially in the case of fourfold dissociation in Ll2 alloys). It should be added that whatever the technique employed in order to analyze dislocation cores (in-situ straining as opposed to static WB or HREM), it is often difficult to assess that TEM observations represent the very configurations that operate in the bulk materials and control its mechanical behaviour; this point has been addressed elsewhere.

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