scholarly journals Numerical Simulation of Shear Behavior and Permeability Evolution of Rock Joints with Variable Roughness and Infilling Thickness

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Jingyi Cheng ◽  
Hongwei Zhang ◽  
Zhijun Wan
Keyword(s):  
Rock Joint ◽  
Shear Behavior ◽  
Thickness Ratio ◽  
Rock Joints ◽  
Hyperbolic Function ◽  
Hydraulic Fractures ◽  
Permeability Evolution ◽  
Joint Roughness ◽  
Shear Process ◽  
Variable Roughness

The mechanical properties and permeability evolution of sand-infilled rock joints during the shear process is an important issue in rock engineering, such as it pertains to hydraulic fractures filled with proppant. Shear can disrupt the preexisting hydraulic and mechanical equilibrium conditions, thus affecting fluid flow. In this study, we simulate the shear behavior of rock joints with variable roughness and sand infilling thickness using the discrete element code PFC2D. Rock joint roughness is evaluated by the joint roughness coefficient (JRC), and sand infilling thickness is evaluated by a thickness ratio (i.e., ratio of infill thickness to rock height) ranging from 0.02 to 0.20. The results show that peak shear strength decreases with the thickness ratio in a relation that can be expressed by a hyperbolic function. We also measure the permeability evolution during shearing and find that the permeability of infilled rock joints increases with both the thickness ratio and JRC.

scholarly journals Experimental Study on Hydromechanical Behavior of an Artificial Rock Joint with Controlled Roughness

2019 ◽  
Vol 11 (4) ◽  
pp. 1014
Author(s):  
Seungbeom Choi ◽  
Byungkyu Jeon ◽  
Sudeuk Lee ◽  
Seokwon Jeon
Keyword(s):  
Rock Mass ◽  
Rock Joint ◽  
Great Influence ◽  
Rock Joints ◽  
In Situ Tests ◽  
Joint Roughness ◽  
Artificial Rock ◽  
Geometric Conditions ◽  
Bedding Planes ◽  
Hydraulic Aperture

Rock mass contains various discontinuities, such as faults, joints, and bedding planes. Among them, a joint is one of the most frequently encountered discontinuities in rock engineering applications. Generally, a joint exerts great influence on the mechanical and hydraulic behavior of rock mass, since it acts as a weak plane and as a fluid path in the rock mass. Therefore, an accurate understanding on joint characteristics is important in many projects. In-situ tests on joints are sometimes consumptive in terms of time and expenses so that the features are investigated by laboratory tests, providing fundamental properties for rock mass analyses. Although the behavior of a joint is affected by both mechanical and geometric conditions, the latter are often limited, since quantitative control on the conditions is quite complicated. In this study, artificial rock joints with various geometric conditions, i.e., joint roughness, were prepared in a quantitative manner and the hydromechanical characteristics were investigated by several laboratory experiments. Based on the results, a prediction model for hydraulic aperture was proposed in the form of ( e h / e m ) 3 = exp ( − 0.0462 c ) × ( 0.8864 ) J R C , which was a function of the mechanical aperture, joint roughness, and contact area. Relatively good agreement between the experimental results and predicted value indicated that the model is capable of estimating the hydraulic aperture properly.

scholarly journals Effect of rock joint roughness on its cyclic shear behavior

2017 ◽  
Vol 9 (6) ◽  
pp. 1071-1084 ◽  
Author(s):  
S.M. Mahdi Niktabar ◽  
K. Seshagiri Rao ◽  
Amit Kumar Shrivastava
Keyword(s):  
Rock Joint ◽  
Shear Behavior ◽  
Joint Roughness ◽  
Cyclic Shear

Scale effect on the anisotropy characteristics of rock joint roughness

2021 ◽  
pp. qjegh2020-066
Author(s):  
Shi-Gui Du ◽  
Kai-Qian Du ◽  
Rui Yong ◽  
Jun Ye ◽  
Zhan-You Luo
Keyword(s):  
Scale Effect ◽  
Rock Joint ◽  
Rock Joints ◽  
Roughness Coefficient ◽  
Scale Dependency ◽  
Joint Roughness Coefficient ◽  
Local Anisotropy ◽  
Joint Roughness ◽  
Threshold Length

Accurate assessment of anisotropy and scale effect of rock joint roughness is essential for evaluating the mechanical behaviour of rock joints. However, in previous studies, how to quantify roughness anisotropy of rock joints remains largely unsolved, and the research about scale effect on roughness anisotropy is not conclusive. A statistical analysis on joint roughness coefficient of different sized profiles was implemented to investigate the scale-dependency of joint roughness. The scale effect on the roughness anisotropy were investigated based on class ratio transform approach. The roughness anisotropy was characterized by local anisotropy and global anisotropy. The global anisotropy tends to be almost constant when the sample size exceeds the stationarity threshold length of 70 cm. The result shows that the global anisotropy is scale-dependent. However, the scale effect on local anisotropy is less apparent. The case study indicates that the class ratio transform approach implies its superiority in roughness anisotropy investigation.

scholarly journals Correlation between the Joint Roughness Coefficient and Rock Joint Statistical Parameters at Different Sampling Intervals

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Man Huang ◽  
Cia-chu Xia ◽  
Peng Sha ◽  
Cheng-rong Ma ◽  
Shi-gui Du
Keyword(s):  
General Formula ◽  
Rock Joint ◽  
Statistical Parameter ◽  
Rock Joints ◽  
Estimation Accuracy ◽  
Roughness Coefficient ◽  
Joint Roughness Coefficient ◽  
Joint Roughness ◽  
The Relationship ◽  
Fitting Parameters

Joint roughness coefficient (JRC) is a major factor that affects the mechanical properties of rock joints. Statistical methods that are used to calculate the JRC increasingly depend on a sampling interval (Δx). The variation rules of fitting parameters a, b, and b/a at different Δx values were analyzed on the basis of the relationship between the JRC and statistical parameter Z2. The relationship between the fitting parameters a and b was deduced in accordance with the ten standard profiles proposed by Barton. Empirical formulas for the JRC, Z2, and Δx were also established. The estimation accuracy of the JRC was the highest in the analysis of Δx values within 0.1–5.0 mm. JRC tests were conducted through inverse value comparative analysis. Results showed that the outcome calculated using the general formula and the JRC inverse values demonstrate improved agreement and verify the rationality of the general formula. The proposed formula can perform rapid and simple JRC calculation within the Δx range of 0.1–5.0 mm using Z2, thereby indicating favorable application prospects.

scholarly journals Neutrosophic Functions of the Joint Roughness Coefficient and the Shear Strength: A Case Study from the Pyroclastic Rock Mass in Shaoxing City, China

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Jun Ye ◽  
Rui Yong ◽  
Qi-Feng Liang ◽  
Man Huang ◽  
Shi-Gui Du
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Rock Joint ◽  
Sampling Bias ◽  
Rock Joints ◽  
Joint Surface ◽  
Pyroclastic Rock ◽  
Roughness Coefficient ◽  
Joint Roughness Coefficient ◽  
Joint Roughness

Many studies have been carried out to investigate the scale effect on the shear behavior of rock joints. However, existing methods are difficult to determinate the joint roughness coefficient (JRC) and the shear strength of rock joints with incomplete and indeterminate information; the nature of scale dependency of rock joints is still unknown and remains an ongoing debate. Thus, this paper establishes two neutrosophic functions of the JRC values and the shear strength based on neutrosophic theory to express and handle the incomplete and indeterminate problems in the analyses of the JRC and the shear strength. An example, including four rock joint samples derived from the pyroclastic rock mass in Shaoxing city, China, is provided to show the effectiveness and rationality of the developed method. The experimental results demonstrate that the proposed neutrosophic functions can express and deal with the incomplete and indeterminate problems of the test data caused by geometry complexity of the rock joint surface and sampling bias. They provide a new approach for estimating the JRC values of the different-sized test profiles and the peak shear strength of rock joints.

Rock Joint Description and Modelling for Prediction of Near-Field Repository Performance

1983 ◽  
Vol 26 ◽  
Author(s):  
Nick Barton ◽  
Khosrow Bakhtar ◽  
Stavros Bandis
Keyword(s):  
Near Field ◽  
Rock Joint ◽  
Block Size ◽  
Shear Behavior ◽  
Rock Joints ◽  
Major Influence ◽  
Nuclear Waste Repository ◽  
Joint Spacing ◽  
Effective Normal Stress ◽  
Wall Strength

ABSTRACTThe shear behavior and normal closure behavior of rock joints have a major influence on the changes in joint conductivity to be expected during the life of a repository. Methods are described for obtaining the joint parameters required to model these conductivity perturbations. They include the joint roughness and the wall strength, which can both be obtained from simple tests on jointed drill core. Examples are shown that illustrate the shear stress-displacement, dilation and conductivity coupling that occurs when a joint of given size is subjected to shear under various levels of effective normal stress. Major increases in conductivity may occur. Examples are also shown that illustrate the stress-closure-conductivity coupling. This comprehensive joint behavior model indicates that important size-effects exist in shear behavior which are related to the joint spacing or effective in situ block size. The discrete modelling of near-field joint and fracture performance is essential for predicting the long-term integrity of a nuclear waste repository.

Non-stationarity, heterogeneity, scale effects, and anisotropy investigations on natural rock joint roughness using the variogram method

2021 ◽  
Author(s):  
Pinnaduwa H. S. W. Kulatilake ◽  
Shi-Gui Du ◽  
Mawuko Luke Yaw Ankah ◽  
Rui Yong ◽  
Desmond Talamwin Sunkpal ◽  
...  
Keyword(s):  
Scale Effects ◽  
Rock Joint ◽  
Joint Roughness ◽  
Natural Rock
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