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.

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 Stress Wave Propagation through Rock Joints Filled with Viscoelastic Medium Considering Different Water Contents

2020 ◽  
Vol 10 (14) ◽  
pp. 4797 ◽  
Author(s):  
Xiaolin Huang ◽  
Shengwen Qi ◽  
Bowen Zheng ◽  
Youshan Liu ◽  
Lei Xue ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Water Content ◽  
Seismic Response ◽  
Transmission Coefficient ◽  
Stress Wave ◽  
Viscoelastic Medium ◽  
Rock Joints ◽  
Stress Wave Propagation ◽  
Multiple Reflections ◽  
Joint Spacing

A rock mass often contains joints filled with a viscoelastic medium of which seismic response is significant to geophysical exploration and seismic engineering design. Using the propagator matrix method, an analytical model was established to characterize the seismic response of viscoelastic filled joints. Stress wave propagation through a single joint highly depended on the water content and thickness of the filling as well as the frequency and incident angle of the incident wave. The increase in the water content enhanced the viscosity (depicted by quality factor) of the filled joint, which could promote equivalent joint stiffness and energy dissipation with double effects on stress wave propagation. There existed multiple reflections when the stress wave propagated through a set of filled joints. The dimensionless joint spacing was the main controlling factor in the seismic response of the multiple filled joints. As it increased, the transmission coefficient first increased, then it decreased instead, and at last it basically kept invariant. The effect of multiple reflections was weakened by increasing the water content, which further influenced the variation of the transmission coefficient. The water content of the joint filling should be paid more attention in practical applications.

scholarly journals Radiation Effects on Materials in the Near-Field of a Nuclear Waste Repository

2000 ◽  
Vol 663 ◽  
Author(s):  
B.X. Gu ◽  
L.M. Wang ◽  
S.X. Wang ◽  
R.C. Ewing
Keyword(s):  
Ion Exchange ◽  
Nuclear Waste ◽  
Radiation Effects ◽  
Ion Beam ◽  
Near Field ◽  
Energetic Electron ◽  
Layered Silicates ◽  
Nuclear Waste Repository ◽  
Layer Spacing ◽  
Waste Repository

ABSTRACTThe long-term radiation effects on materials in the near-field of a nuclear waste repository have been evaluated using accelerated laboratory experiments with energetic electron or ion beam irradiation. The materials studied include: zeolites, layered silicates (smectite clay and mica), as well as crystalline silicotitanate (CST) which is an important ion exchange material for the chemical separation of high-level liquid radioactive wastes.In situ transmission electron microscopy (TEM) during irradiation by energetic electrons and ions has shown that all of the studied materials are susceptible to irradiation-induced amorphization. At room temperature, complete amorphization was observed after ionizing doses of 1010 ∼ 1012 Gy or displacement doses on the order of 0.1 dpa (equivalent to doses received in 400-1,000 years for a high-loading nuclear waste form). Amorphization may be preceded or accompanied by dehydration, layer spacing reduction and gas bubble formation. In the case of zeolites, CST and some layered silicates, radiation effects are significantly enhanced at higher temperatures. Our experiments have shown that amorphization or even partial amorphization will cause a dramatic reduction in ion exchange and sorption/desorption capacities for radionuclides, such as Cs and Sr. Because the near-field or chemical processing materials (e.g. zeolites or CST) will receive a substantial radiation dose after they have incorporated radionuclides, our results suggest that radiation effects may, in some cases, retard the release of sorbed or ion-exchanged radionuclides.

Verification of UDEC Modeling 1-D Wave Propagation in Rocks

2011 ◽  
Vol 90-93 ◽  
pp. 1998-2001
Author(s):  
Wei Dong Lei ◽  
Xue Feng He ◽  
Rui Chen
Keyword(s):  
Wave Propagation ◽  
Analytical Solution ◽  
Transmission Coefficient ◽  
Method Of Characteristics ◽  
Rock Joint ◽  
Rock Joints ◽  
Dynamic Problems ◽  
The Method Of Characteristics ◽  
Elastic Rock ◽  
D Wave

Three cases for 1-D wave propagation in ideal elastic rock, through single rock joint and multiple parallel rock joints are used to verify 1-D wave propagation in rocks. For the case for 1-D wave propagation through single rock joint, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the analytical solution. For 1-D wave propagation through multiple parallel joints, the magnitude of transmission coefficient obtained from UDEC results is compared with that obtained from the method of characteristics. For all these cases, UDEC results agree well with results from the analytical solutions and the method of characteristics. From these verification studies, it can be concluded that UDEC is capable of modeling 1-D dynamic problems in rocks.

scholarly journals Scale Dependence of Waviness and Unevenness of Natural Rock Joints through Fractal Analysis

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Yingchun Li ◽  
Shengyue Sun ◽  
Hongwei Yang
Keyword(s):  
Surface Roughness ◽  
Rock Joint ◽  
Fractal Dimensions ◽  
Window Size ◽  
Scale Dependence ◽  
Rock Joints ◽  
Joint Surface ◽  
Triangular Prism ◽  
Natural Rock ◽  
Waviness And Unevenness

The scale dependence of surface roughness is critical in characterising the hydromechanical properties of field-scale rock joints but is still not well understood, particularly when different orders of roughness are considered. We experimentally reveal the scale dependence of two-order roughness, i.e., waviness and unevenness through fractal parameters using the triangular prism surface area method (TPM). The surfaces of three natural joints of granite with the same dimension of 1000 mm×1000 mm are digitised using a 3D laser scanner at three different measurement resolutions. Waviness and unevenness are quantitatively separated by considering the area variation of joint surface as grid size changes. The corresponding fractal dimensions of waviness and unevenness in sampling window sizes ranging from 100 mm×100 mm to 1000 mm×1000 mm at an interval of 100 mm×100 mm are determined. We find that both the fractal dimensions of waviness and unevenness vary as the window size increases. No obvious stationarity threshold has been found for the three rock joint samples, indicating the surface roughness of natural rock joints should be quantified at the scale of the rock mass in the field.

In situ experiments on the performance of near-field for nuclear waste repository at KURT

2012 ◽  
Vol 252 ◽  
pp. 278-288 ◽  
Author(s):  
Won-Jin Cho ◽  
Jin-Sub Kim ◽  
Changsoo Lee ◽  
Sangki Kwon ◽  
Jong-Won Choi
Keyword(s):  
Nuclear Waste ◽  
Near Field ◽  
Nuclear Waste Repository ◽  
In Situ Experiments ◽  
Waste Repository
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