Permeability evolution of fracture during slipping under normal stress condition

2018 ◽  
pp. 235-242
Author(s):  
Q. Zhang ◽  
X.C. Li
Keyword(s):  
Normal Stress ◽  
Stress Condition ◽  
Permeability Evolution

scholarly journals Permeability Evolution of an Intact Marble Core during Shearing under High Fluid Pressure

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Yuan Wang ◽  
Yu Jiao ◽  
Shaobin Hu
Keyword(s):  
Normal Stress ◽  
Laser Scanning ◽  
Shear Failure ◽  
Fluid Pressure ◽  
Shear Displacement ◽  
Permeability Evolution ◽  
Fracture Permeability ◽  
Effective Normal Stress ◽  
High Fluid ◽  
High Fluid Pressure

The progressive shear failure of a rock mass under hydromechanical coupling is a key aspect of the long-term stability of deeply buried, high fluid pressure diversion tunnels. In this study, we use experimental and numerical analysis to quantify the permeability variations that occur in an intact marble sample as it evolves from shear failure to shear slip under different confining pressures and fluid pressures. The experimental results reveal that at low effective normal stress, the fracture permeability is positively correlated with the shear displacement. The permeability is lower at higher effective normal stress and exhibits an episodic change with increasing shear displacement. After establishing a numerical model based on the point cloud data generated by the three-dimensional (3D) laser scanning of the fracture surfaces, we found that there are some contact areas that block the percolation channels under high effective stress conditions. This type of contact area plays a key role in determining the evolution of the fracture permeability in a given rock sample.

Experimental Study on Shear Mechanical Characteristics of Cohesionless Granular Material

2011 ◽  
Vol 90-93 ◽  
pp. 230-233
Author(s):  
Hong Chun Xia ◽  
Guo Qing Zhou ◽  
Ze Chao Du
Keyword(s):  
Shear Stress ◽  
Normal Stress ◽  
Mechanical Characteristics ◽  
Stress Condition ◽  
Fine Sand ◽  
Shear Displacement ◽  
Direct Shear ◽  
Steel Particle ◽  
High Normal Stress ◽  
Fine Gravel

The direct shear mechanical characteristics of gravel, sand and steel particle were studied systematically using DRS-1 high normal stress direct and residual shear apparatus. The results show that the shear mechanical characteristics of gravel, sand and steel particle is different under different normal stress condition. For steel particle, the curves of shear stress-shear displacement present strain softening regardless of the magnitude of normal stress, and the shear displacement corresponding to the peak shear stress increases with the normal stress. Under low normal stress condition, the volume of fine gravel and steel particle expand, but the fine sand contracts at the beginning of direct shear and then contracts. Under high normal stress condition, the volume of steel particle contracts at the beginning of the direct shear and then contracts, but the fine sand and fine gravel contract throughout the direct shear. The particle breakage has significant effect on the shear strength of fine sand and fine gravel. Under the same high normal stress condition, the volume of fine gravel is greater than that of fine sand, which indicates that the fine gravel is easier to be crushed than the fine sand.

Experimental study of impact of shearing velocity and effective normal stress on post-shearing permeability evolution of silica fault gouges

2020 ◽  
Vol 789 ◽  
pp. 228521
Author(s):  
Sho Kimura ◽  
Shohei Noda ◽  
Takuma Ito ◽  
Jun Katagiri ◽  
Hiroaki Kaneko ◽  
...  
Keyword(s):  
Experimental Study ◽  
Normal Stress ◽  
Permeability Evolution ◽  
Effective Normal Stress ◽  
Fault Gouges

scholarly journals Analysis of a Methodology for Torsional Test under Normal Stress and Shear Performance for Asphalt Mixtures

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Jun Xie ◽  
Yiqun Zhan ◽  
Yifan Wang
Keyword(s):  
Shear Strength ◽  
Normal Stress ◽  
Shear Test ◽  
Stress Condition ◽  
Asphalt Mixture ◽  
Friction Angle ◽  
Asphalt Mixtures ◽  
Test Method ◽  
Shear Performance ◽  
Torsional Test

Insufficient shear performance in an asphalt mixture is a primary reason for rutting deformation and pavement surface longitudinal cracking. Thus, it is important to choose a suitable shear test method to evaluate shear performance in an asphalt mixture. Current testing methods mainly evaluate the bonding strength between asphalt layers, and the current shear test method for an asphalt mixture is disadvantaged by high equipment cost and complicated procedures. Our study proposes a torsional test method under normal stress condition, and evaluation was done for four types of asphalt mixture under different temperature conditions. Through the mechanical analysis, the calculation formulas for shear strength and shear parameters (cohesion and internal friction angle) for the torsional test under a normal stress condition were obtained. Testing results were also obtained for shear strength, shear modulus, and cohesion and internal friction angle of the asphalt mixtures. Experimental testing indicated that the method was able to provide repeatable results for the shear resistance of asphalt mixtures at different temperatures and also reflected the difference in shear performance of the various asphalt mixtures and the influence of temperature on shear performance. The failure mode of the specimen was the appearance of an oblique crack of about 45° from the vertical axis after the specimen was destroyed, which accorded with shear failure characteristics. A shear fatigue model was obtained considering different shear stress levels. The torsional test method under normal stress formed a compression-shear action on the specimen by applying torque and normal stress and was used to evaluate the shear performance of the asphalt mixtures.

Permeability and Effective Stress in Dipping Gas Shale Formation With Bedding—Experimental Study

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Yufei Chen ◽  
Changbao Jiang ◽  
Guangzhi Yin ◽  
Andrew K. Wojtanowicz ◽  
Dongming Zhang
Keyword(s):  
Normal Stress ◽  
Effective Stress ◽  
Bedding Plane ◽  
Permeability Change ◽  
Permeability Evolution ◽  
Tangential Stresses ◽  
Significance Levels ◽  
Percent Contribution ◽  
Shale Formation ◽  
Shale Permeability

Abstract Shale gas well deliverability and economics depend on extremely low permeability that is not only dependent on the rock bedding trend but also controlled by in situ stresses. The purpose of this study was to determine relative contributions of normal and tangential stresses with respect to the rock bedding plane on permeability evolution of shale. The study involved an analysis of the rock bedding structure, followed by triaxial testing of rock samples and theoretical modeling. Also simulated were the effects of stress-bedding and load cycling. The results showed shale permeability reduction during the stress loading process and its gradual recovery during the unloading process. Permeability change was more pronounced in response to normal stress but some effects of the tangential stresses were also observed. Moreover, a theoretical model was derived to describe permeability change with effective stress in the presence of normal and tangential stresses. The model was empirically matched with the experimental results. The assessment of relative contributions of normal and tangential stresses was quantified with the analysis of variance (ANOVA). The analysis revealed significance levels of normal stress, and two tangential stresses σt1 and σt2 on shale permeability as 81%, 5%, and 14%, respectively. An almost 20-percent contribution of tangential stress loading to permeability response indicates a need for the improvement in computing effective stress. Therefore, a new method was suggested to determine effective stress when predicting permeability evolution of shale.

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