scholarly journals Deformation Mechanism of the Coal ahead of Fully Mechanized Caving Face under High-Intensity Mining Condition

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Can Zhao ◽  
Liang Chen ◽  
Bing Wu ◽  
Jingui Zhang ◽  
Dahe Yan ◽  
...  

In order to study the coal deformation and failure mechanism in fully mechanized caving face under the high-intensity mining, based on the equivalent mechanical model of transversely isotropic cylindrical coal with fractures, the equivalent equations for axial, radial, and volume strains of coal sample loaded in linear elastic and plastic stages were derived in this paper. The equivalent mechanical model shows good reliability through the conventional triaxial experiment. Taking the N1206 workface in Yuwu coal mine of Luan group as the example, we have simulated the stress concentration factor of the coal body ahead of the working face with FLAC and divided three regions according to stress distribution in coal mining. Mathematical equations were derived to express the horizontal and vertical stress, which provide theoretical guidance of the stress paths in triaxial experiment about real mining stress environment simulation. Experimental results show that the volume strain’s value is about 0.4% in the coal mass deformation progress of axial compression increasing slowly area. In axial compression increasing rapidly area, the volume strain’s value varies from 0.41% to 0.27%, and the radical strain changes from compression deformation to expansion deformation gradually. The volume strain of coal sample increases sharply in axial compression releasing rapidly area; meanwhile, there are good linear relationships between Poisson’s ratio and axial strain and radial strain.

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 717
Author(s):  
Kai Wang ◽  
Qichao Fu ◽  
Xiang Zhang ◽  
Hengyi Jia

Through laboratory simulation experiments, this paper studies the influence of different temperature and stress conditions on strain changes of raw coal samples induced by the CO2 adsorption with tri-axial creep-seepage and adsorption-desorption experimental system. Comparing and analyzing the experimental results, the study shows that: (1) within a certain time, the axial and radial strain of the raw coal sample induced by CO2 adsorption both show a growing trend as the adsorption time increases and the strain of the raw coal sample for CO2 adsorption is obvious anisotropy; (2) at the same point in time, the greater the axial effective stress, the smaller the axial strain increasing rate of the loaded coal sample during CO2 adsorption process and the smaller the value of axial deformation; (3) during the adsorption process, the volume strain of raw coal sample decreases with the increasing of temperature, namely, the adsorption capacity of raw coal sample decreases with the increasing of temperature.


Author(s):  
Philip Boughton ◽  
James Merhebi ◽  
C. Kim ◽  
G. Roger ◽  
Ashish D. Diwan ◽  
...  

An elastomeric spinal disk prosthesis design (BioFI™) with vertebral interlocking anchors has been modified using an embedded TiNi wire array. Bioinert styrenic block copolymer (Kraton®) and polycarbonate urethane (Bionate®) thermoplastic elastomer (TPE) matrices were utilized. Fatigue resistant NiTi wire was pretreated to induce superelastic martensitic microstructure. Stent-like helical structures were produced for incorporation within homogenous TPE matrix. Composite prototypes were fabricated in a vacuum hot press using transfer moulding techniques. Implant prototypes were subject to axial compression using a BOSE ® ELF3400. The NiTi reinforced implants exhibited reduction in axial strain, compliance, and creep compared to TPE controls. The axial properties of the NiTi reinforced Bionate® BioFI™ implant best approximated those of a spinal disk followed by Kraton®-NiTi, Bionate® and Kraton® prototypes. An ovine lumbar segment biomechanical model was used to characterize the disk prosthesis prototypes. Specimens were subject to 7.5Nm pure moments in axial rotation, flexion-extension and lateral bending with a custom jig mounted on an Instron® 8874. The motion preserving ligamentous nature of this arthroplasty prototype was not inhibited by NiTi reinforcement. Joint stiffness for all prototypes was significantly less than the intact and discectomy controls. This was due to lack of vertebral anchor rigidity rather than BioFI™ motion segment matrix type or reinforcement. Implant stress profiles for axial compression and axial torsion conditions were obtained using finite element methods. The biomechanical testing and finite element modelling both support existing BioFI™ design specifications for higher modulus vertebral anchors, endplates and motion segment periphery with gradation to a low modulus core within the motion segment. This closer approximation of the native spinal disk form translates to improvements in prosthesis biomechanical fidelity and longevity. Axial compressive strain induced within a TiNi reinforced Kraton® BioFI™ was found to be linearly proportional to the NiTi helical coil electrical resistance. This neural network capability delivers opportunities to monitor and telemeterize in situ multiaxis joint structural performance and in vivo spine biomechanics.


2013 ◽  
Vol 135 (1) ◽  
Author(s):  
J. S. Love ◽  
M. J. Tait

Tuned liquid dampers (TLDs) utilize sloshing fluid to absorb and dissipate structural vibrational energy, thereby reducing wind induced dynamic motion. By selecting the appropriate tank length, width, and fluid depth, a rectangular TLD can control two structural sway modes simultaneously if the TLD tank is aligned with the principal axes of the structure. This study considers the influence of the TLD tank orientation on the behavior of a 2D structure-TLD system. The sloshing fluid is represented using a linearized equivalent mechanical model. The mechanical model is coupled to a 2D structure at an angle with respect to the principal axes of the structure. Equations of motion for the system are developed using Lagrange’s equation. If the TLD and structure are not aligned, the system responds as a coupled four degree of freedom system. The proposed model is validated by conducting structure-TLD system tests. The predicted and experimental structural displacements and fluid response are in agreement. An approximate method is developed to provide an initial estimate of the structural response based on an effective mass ratio. The results of this study show that for small TLD orientation angles, the performance of the TLD is insensitive to TLD orientation.


2015 ◽  
Vol 85 ◽  
pp. 1175-1183 ◽  
Author(s):  
Yu Liu ◽  
Daogang Lu ◽  
Junjie Dang ◽  
Shu Wang ◽  
Xiaojia Zeng

Author(s):  
Yuanjin Ji ◽  
Lihui Ren ◽  
Jian Wang ◽  
Dao Gong

The wheel–rail contact can be found in two patterns. In the first pattern, the treads of both wheels are in contact with the two top surfaces of the ^-shaped guide rail; in the second pattern, the treads of both wheels are in contact with the two top surfaces of the ^-shaped guide rail, and the wheel edge is in contact with the guide rail web on one side. Based on these findings, an equivalent mechanical model with four unilateral springs is proposed to describe the wheel–rail contact. Additionally, a dynamic model of the Translohr tramway is established using Matlab/Simulink. The wheel–rail contact in a tramway moving along curves with different radii is calculated using simulation, and the results obtained are consistent with the observations and results of field measurements. The effects of various factors, including curve radius, tram speed, guide rail pre-pressure, and guide rod length, on the side wear of the guide rail were investigated. The results revealed that curve radius and tram speed are the critical factors affecting rail track side wear. These two factors can qualitatively determine rail track side wear, while other factors can only quantitatively affect the degree of rail track side wear.


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