scholarly journals A Novel True Triaxial Apparatus for Testing Shear Seepage in Gas-Solid Coupling Coal

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Gang Wang ◽  
Pengfei Wang ◽  
Yangyang Guo ◽  
Wenxin Li
Keyword(s):  
Shear Stress ◽  
Principal Stress ◽  
Intermediate Principal Stress ◽  
Stress Conditions ◽  
Shear Displacement ◽  
Displacement Curve ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
Gas Seepage ◽  
True Triaxial Apparatus

To study the effects of shear stress on the mechanical and seepage properties of gas-bearing coal in three-dimensional stress conditions, a novel true triaxial apparatus (TTA) was developed for the rigid loading of the major principal stress σ1 and the intermediate principal stress σ2, and for the flexible loading of the minor principal stress σ3. Both the upper and lateral pressure heads do not interfere with each other when loading σ1 and σ2. The control and measurement of gas flow sealed effectively in coal samples were achieved by using a gas seepage system. The TTA was used to perform a series of experiments on shear seepage in coal samples under true triaxial stress conditions. The experimental results about coal’s shear failure modes, shear stress-shear displacement curve, and permeability-shear displacement curve all showed that the TTA with its better accuracy and reliability had advantages in studying the effects of both the intermediate principal stress and shear deformation on the mechanical properties of coal samples and on the characteristics of gas seepage. Thus, it could provide a new test means for further studies on shear-induced seepage in the gas-solid coupling coal.

scholarly journals Effect of Intermediate Principal Stress on the Strength, Deformation, and Permeability of Sandstone

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2694 ◽  
Author(s):  
Zhenlong Song ◽  
Minghui Li ◽  
Guangzhi Yin ◽  
Pathegama Ranjith ◽  
Dongming Zhang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Principal Stress ◽  
Intermediate Principal Stress ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Mechanical Behaviors ◽  
Seepage Velocity ◽  
True Triaxial ◽  
Gas Seepage ◽  
True Triaxial Stress

Although the mechanical behaviors and flow aspects of sandstone have been previously investigated, studies of the effect of the intermediate principal stress (σ2) on the strength, deformation, and permeability of sandstone are lacking. In this work, the mechanical behaviors and permeability of sandstone under true triaxial stress conditions were investigated using a newly developed true triaxial geophysical apparatus. The experimental results showed that with increasing σ2, the peak strength, octahedral effective normal stress, and octahedral effective shear stress of the sandstone increased, and the rate of increase decreased. This is because a larger intermediate principal stress coefficient b has an inhibitory effect on rock strength. In our study, as the ratio of σ2/σ3 increased, the specimen entered compressive strain in the σ2 direction during the first stress drop. The stress and strain path deviations occur during rock failure. The amount of deviation increased as the σ2 increased before the peak stress. This phenomenon indicates that elastic mechanics are not suitable for understanding this sandstone rock during its failure. The permeability evolution of the sandstone under true triaxial stress conditions was measured and analyzed to investigate the effect of σ2. During the complete true triaxial stress-strain experiments, the variation we found in gas seepage velocity could be divided into two stages. Before the first pressure drop, the gas seepage velocity was mainly affected by volume strain. After the first pressure drop, the seepage velocity was affected by the deviator strain, which can change the seepage channels.

A New True Triaxial Apparatus

Géotechnique ◽  
1969 ◽  
Vol 19 (2) ◽  
pp. 307-309 ◽  
Author(s):  
E. C. Hambly
Keyword(s):  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus

A Novel True Triaxial Apparatus to Study the Geomechanical and Fluid Flow Aspects of Energy Exploitations in Geological Formations

2016 ◽  
Vol 49 (12) ◽  
pp. 4647-4659 ◽  
Author(s):  
Minghui Li ◽  
Guangzhi Yin ◽  
Jiang Xu ◽  
Wenpu Li ◽  
Zhenlong Song ◽  
...  
Keyword(s):  
Fluid Flow ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
Geological Formations

Damping-ratio measurements by the spectral-ratio method

2006 ◽  
Vol 43 (11) ◽  
pp. 1180-1194 ◽  
Author(s):  
Yu-Hsing Wang ◽  
Wai Man Yan ◽  
Kai Fung Lo
Keyword(s):  
Damping Ratio ◽  
Near Field ◽  
Spectral Ratio ◽  
Ratio Method ◽  
Bender Elements ◽  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus ◽  
Spectral Ratio Method ◽  
Near Field Effect

In this paper, bender elements are used as sensors to measure the damping ratio of soil by the spectral-ratio method. The results of numerical and physical experiments suggest that adequate measurement precision can be achieved by reducing the two types of inherent biases arising from (i) the near-field effect and (ii) the different transfer functions of the two receiver bender elements. The first bias can be avoided by setting sensors to r1/λ ≥ 2.0 and r1/r2 ≥ 2.0, where r1 and r2 are the distances between the source and the first and second receivers, respectively; and λ is the wavelength. The second bias can be minimized by modifying the original spectral-ratio method to accommodate the self-healing technique. The damping ratios, measured by this modified method, obtained from the experiment conducted in a tailor-made, true-triaxial apparatus are very similar to those obtained from resonant column tests under the same state of stress.Key words: bender element, damping ratio, spectral-ratio method, near-field effect, true-triaxial apparatus.

Simulation of Pressuremeter Shearing Mode by True Triaxial Apparatus

2007 ◽  
Vol 30 (2) ◽  
pp. 100453
Author(s):  
LD Suits ◽  
TC Sheahan ◽  
TH Seah ◽  
D Shrestha
Keyword(s):  
True Triaxial ◽  
Triaxial Apparatus ◽  
True Triaxial Apparatus
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