• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.109-118
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition. displacement. groundwater flow conditions have been altered due to the excavation. Various studies have been carried out on EDZ, but most studies have been focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the' hydraulic EDZ' was defined as the rock Lone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation. And hydraulic EDZ (hydraulic aperture changed zone) estimated by two-dimensional DEM program was considered in three-dimensional DFN model. From this approach the groundwater flow characteristics corresponding to hydraulic aperture change were examined. Together. a parametric study was performed to examine the boundary conditions that frequently used in DFN analysis such as constant head or constant flux condition. According to the numerical analysis, hydraulic aperture change induced by the hydraulic-mechanical interaction becomes one of the most important factors Influencing the hydraulic behavior of jointed rock masses. And also from this study, we suggest the proper boundary condition in three-dimensional DFN model.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.26-36
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• 1998

To assess the groundwater flow near high-level radioactive waste repositories, it is important to understand the effect of coupling among thermal, hydraulic, and mechanical effects. In this paper, detailed mathematical approach to model the groundwater flow near the waste form surrounded by buffer, influenced by decay heat of radioactive waste along with stress change is developed. Two cases(1) before the full expansion of buffer and (2) after the full expansion of buffer are modelled. Based on the mathematical models in this paper, detailed numerical study shall be pursued later.

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.255-267
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• 2001

A comparison study is performed to understand the coupling behavior of the thermal, hydraulic, and mechanical interactions in the vicinity of an underground radwaste repository, assumed to be located at a depth of 500 m, within a granitic rock mass with a 58$^{\circ}$ dipping fault passing through the roof-wall intersection of the repository cavern. The two dimensional universal distinct element code, UDEC is used for the analysis. The model includes a granitic rock meas, a canister with PWR spent fuels surrounded by the compacted bentonite inside a deposition hole, and the mixed bentonite backfilled in the rest of the space within a repository cavern. The coupling behavior of hydromechanical, thermomechanical, and thermohydromechanical interaction has been studied and compared. The effect of the time-dependent decaying heat, from the radioactive materials in PWR spent fuels, on the repository and its surroundings has been studied. A steady state flow algorithm is used for the hydraulic analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.133-141
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement, groundwater flow conditions have been altered due to the processes induced by the excavation. Various studies have been carried out on EDZ, but most studies have focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the 'hydraulic EDZ' was defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation by using H-M coupling analysis. Fundamental principles of distinct element method (DEM) were used in the analysis. In the same groundwater level, the behavior of hydraulic aperture near the cavern was analyzed for different stress ratios, initial apertures, fracture angles and fracture spacings by using a two-dimensional DEM program. We evaluate the excavation induced hydraulic aperture change. Using the results of the study, hydraulic EDZ was defined as an elliptical shape model perpendicular to the joint.

• Tunnel and Underground Space
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• v.21 no.1
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• pp.66-81
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• 2011

In this study, it was aimed to develop a thermal-hydraulic-mechanical coupled fracture mechanics code that models a fracture initiation, propagation and failure of underground rock mass due to thermal and hydraulic loadings. The development was based on a 2D FRACOD (Shen & Stephasson, 1993), and newly developed T-M and H-M coupled analysis modules were implemented into it. T-M coupling in FRACOD employed a fictitious heat source and time-marching method, and explicit iteration method was used in H-M coupling. The validity of developed coupled modules was verified by the comparison with the analytical result, and its applicability to the fracture initiation and propagation behavior due to temperature changes and hydraulic fracturing was confirmed by test simulations.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.522-531
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• 2002

In order to study the thermal-hydraulic behavior of the cable-in-conduit-conductor (CICC), a numerical model has been developed. In the model, the high heat transfer approximation between superconducting strands and supercritical helium is adopted. The strong coupling of heat transfer at the front of normal zone generates a contact discontinuity in temperature and density. In order to obtain the converged numerical solutions, a moving mesh method is used to capture the contact discontinuity in the short front region of the normal zone. The coupled equation is solved using the finite element method with the artificial viscosity term. Details of the numerical implementation are discussed and the validation of the code is performed for comparison of the results with thse of GANDALF and QSAIT.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.59-67
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• 2003

In this study, the change in hydraulic conductivity according to the changes in the contact area, aperture, confining pressure and temperature was observed to improve the reliability of the analysis of underground water flow. Also, the mechanical and thermal properties of domestic crystalline rocks in a great depth were obtained. It was found that the averaged intial aperture ranged from 544.33${\mu}{\textrm}{m}$ to 898.62${\mu}{\textrm}{m}$ and it followed a log-normal distribution. The hydraulic conductivity decreased with the increase of normal stress on the fracture surface and the hydraulic conductivity decreased as temperature increased. The change in hydraulic conductivity was strongly correlated with the change in contact area. It was verified by experiments that hydraulic conductivity was inversely proportional to the contact area. The measured mechanical and thermal properties were very close to the existing typical properties of domestic granites.

• Journal of Drive and Control
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• v.17 no.4
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• pp.113-124
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• 2020

Most of the work of construction equipment and agricultural machinery is done in off-road conditions. Autonomous driving required in these conditions uses GPS sensors, and PID controllers to control their speed and position. The hydrostatic steering, which is composed of a PSU, hydraulic hoses, and cylinders, rather than a mechanical coupling is used in these equipments. The PSU plays a key role in hydrostatic steering. Precise control of the position under various conditions requires detailed behavioral analysis of the basic components and operation. Two Gerotor PSU is now a commonly used safer option. The components of the PSU can be divided into mechanical and hydraulic actuating elements by its behavior. Since the system is combined by mechanical and hydraulic elements, the modelings are performed using Amesim, which is one of the most effective for the multi-domain dynamic system analysis. To confirm the validity of the model, input torque and pressures are checked with varying steering speed. The opening and the steering speed of normal and newly designed control valve set is investigated with the effect of centering spring force and friction. Finally, simulation results with fully detailed model with two gerotors are analyzed and compared with simple model.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.17-25
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• 1998

This paper investigates coupled thermal, mechanical and hydraulic phenomena in deep rock mass especially for underground heat storage system. Firstly, concepts of underground heat storage were presented and coupling phenomena in this area were illustrated. In order to understand the basic mechanism of thermal, hydraulic and deformation behavior in rock cavern disturbed by thermal gradient about 10$0^{\circ}C$, various numerical experiments were conducted using several codes. The study involves the behavior of fractured rock mass including rock joint. In spite of the limitation of codes modelling fully coupled effects, these codes could be applied in analysis of underground heat storage. The heat loss in rock mass, which is a major factor in heat storage, is insignificant in all results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.282-287
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• 2004

Noise and vibrations in the pipe systems may be arisen from pumps. compressors, etc. The source mechanism is classified with the mechanical and hydraulic. Mechanical vibrations may be excited by the unbalance in rotating machinery. Hydraulic source may be generated in the turbulent flow. The vibro-acoustic behaviour of flexible, fluid-filled pipe system is a very complex and determined by two parameters: the frequency and the mass ratio of fluid and pipe wall. As the frequency increases, the mode number in the pipe increases. The mass ratio is close to one, the structure and the fluid are strongly coupled. In ease the diameter is very small to the length of pipe, the behaviour of pipe is same as a beam. The finite element formulation when the fluid and the structure are coupled is derived by using beam element. The Numerical results are compared with the package (Sysnoise) which is using the shell element.