• Title/Summary/Keyword: Discrete element analysis

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Groundwater Flow Analysis around Hydraulic Excavation Damaged Zone (수리적 굴착손상영역에서의 지하수유동 특성에 관한 연구)

  • Park, Jong-Sung;Ryu, Dong-Woo;Ryu, Chang-Ha;Lee, Chung-In
    • 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.

Numerical Analysis of Horizontal Collector Well in Riverbank Filtration (수평 방사형 집수정 활용 강변여과 취수 수치 분석)

  • Kim, Hyoung-Soo;Jeong, Jae-Hoon
    • Journal of Soil and Groundwater Environment
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    • v.14 no.1
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    • pp.1-10
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    • 2009
  • Groundwater flow due to intake of horizontal collector well in riverbank filtration site was analyzed by use of numerical groundwater modeling program (FEFLOW 5.1). Drawdowns of groundwater table nearby collector well were evaluated according to variations of several conditions; pumping rate, thickness of aquifer, offset distance from well to shore line of stream, conductance of streambed. It is observed that the drawdowns of groundwater table are clearly changed according to the variations of these conditions. The results of sensitive analysis shows that the thickness of alluvial aquifer and the offset distance are more sensitive than the conductance of streambed in evaluation of drawdown. This result implies that hydrogeological conditions, as like thickness of aquifer and its distribution in the site are important factors in site selection and evaluating the availability of riverbank filtration intake using horizontal collector well system. It is also revealed that numerical modeling using FEFLOW with 1-D discrete element feature can give efficient quantitative evaluation of horizontal collector well and estimation of availability of riverbank filtration site.

Damage Analysis of Nearby Structures with the Consideration of Tunnel Construction Conditions in Sandy and Clayey Ground (모래 및 점토지반에서 터널시공조건을 고려한 인접구조물의 손상도 분석)

  • Son, Moorak;Yun, Jongcheol
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.1C
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    • pp.53-63
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    • 2011
  • This paper investigates the effects of tunnelling-induced ground movements on nearby structures, considering soil-structure interactions of different ground (loose sand, dense sand, soft clay, stiff clay) and construction conditions (ground loss). The response of four-story block structures, which are subjected to tunnelling-induced ground movements, has been investigated in different ground and construction conditions (ground loss) using numerical analysis. The structures for numerical analysis has been modelled using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four-story block structures has been investigated with a ground movement magnitude and compared in terms of ground and construction conditions (ground loss) considering the magnitude of deformations and cracks in structures. In addition, the damage levels, which are possibly induced in structures, has been provided in terms of ground and construction conditions (ground loss) using the state of strain damage estimation criterion (Son and Cording, 2005). The results of this study will provide a background for better understandings for controlling and minimizing building damage on nearby structures due to tunnelling-induced ground movements.

Change of Fractured Rock Permeability due to Thermo-Mechanical Loading of a Deep Geological Repository for Nuclear Waste - a Study on a Candidate Site in Forsmark, Sweden

  • Min, Ki-Bok;Stephansson, Ove
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2009.06a
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    • pp.187-187
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    • 2009
  • Opening of fractures induced by shear dilation or normal deformation can be a significant source of fracture permeability change in fractured rock, which is important for the performance assessment of geological repositories for spent nuclear fuel. As the repository generates heat and later cools the fluid-carrying ability of the rocks becomes a dynamic variable during the lifespan of the repository. Heating causes expansion of the rock close to the repository and, at the same time, contraction close to the surface. During the cooling phase of the repository, the opposite takes place. Heating and cooling together with the, virgin stress can induce shear dilation of fractures and deformation zones and change the flow field around the repository. The objectives of this work are to examine the contribution of thermal stress to the shear slip of fracture in mid- and far-field around a KBS-3 type of repository and to investigate the effect of evolution of stress on the rock mass permeability. In the first part of this study, zones of fracture shear slip were examined by conducting a three-dimensional, thermo-mechanical analysis of a spent fuel repository model in the size of 2 km $\times$ 2 km $\times$ 800 m. Stress evolutions of importance for fracture shear slip are: (1) comparatively high horizontal compressive thermal stress at the repository level, (2) generation of vertical tensile thermal stress right above the repository, (3) horizontal tensile stress near the surface, which can induce tensile failure, and generation of shear stresses at the comers of the repository. In the second part of the study, fracture data from Forsmark, Sweden is used to establish fracture network models (DFN). Stress paths obtained from the thermo-mechanical analysis were used as boundary conditions in DFN-DEM (Discrete Element Method) analysis of six DFN models at the repository level. Increases of permeability up to a factor of four were observed during thermal loading history and shear dilation of fractures was not recovered after cooling of the repository. An understanding of the stress path and potential areas of slip induced shear dilation and related permeability changes during the lifetime of a repository for spent nuclear fuel is of utmost importance for analysing long-term safety. The result of this study will assist in identifying critical areas around a repository where fracture shear slip is likely to develop. The presentation also includes a brief introduction to the ongoing site investigation on two candidate sites for geological repository in Sweden.

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Layout Principles of Renaissance Classicism Architectural Style and Its Application on Modern Fashion Design - Focused on Classic Style Fashion after the Year 1999 - (르네상스 고전주의 건축양식의 조형원리와 현대패션디자인에의 적용 - 1999년 이후 클래식 스타일 패션을 중심으로 -)

  • Lee, Shin-Young
    • The Research Journal of the Costume Culture
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    • v.18 no.2
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    • pp.261-276
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    • 2010
  • The analysis of an art trend in the principle dimension starts by observing the object of work in the perspective of formative composition and recognizing it as a universal system. It can be said that it is consistent with an interpretation method for a form theory of formal history by Heinrich W$\ddot{o}$lfflin, a leading form critic in art criticism. Hence, the purpose of this study was to find out what are the formative principles in Renaissance Classicism as a design principle to be applicable to modern fashion by reviewing the formative characteristics of Renaissance Classicism Architecture with which W$\ddot{o}$lfflin directly dealt. As for the theoretical literature review, I used W$\ddot{o}$lfflin's theoretical framework and looked at the Renaissance Classicism Architecture that he studied and examined the possibility of utilizing his theory as a layout principle and the characteristics. As for analysis of design cases, I applied the aforementioned architecture layout principle to modern fashion and conducted case study analysis to delve into distinctive layout principles found in fashion. The study showed that the Renaissance Classicism Architectural Style is marked by linearity, planarity, closing and multiple unity: linearity was expressed in the observation form in fixed frontal view and an emphasis on a tangible silhouette homeogenous and definite line structures; planarity was achieved in the form of paralleled layers of frontal view element, planarity style, and identical and proportional repetition of various sizes.; closing signified the pursuit of complete and clear regularity, and architecture developed in a constructive phase through organizational inevitability and absolute invariability.; multiple unity was expressed in self-completedness and independent parallel of discrete forms and harmony of emphasized individual elements in a totality. Applying these layout characteristics of the Renaissance Classicism Architectural style and to see their individual expressive features, I found out that in adopting layout principles of the Renaissance Classicism Architecture to modern fashion, it turned out to be an emphasis of individual silhouettes, a flattened space, completed objects, organic harmony among independent parts: the emphasis of individual silhouettes was expressed in individual definitiveness of formative lines of clothes in accordance with body joints and an emphasis on formative lines of clothes; the flattened space was marked by single layer structure, planarity of elements of clothes, and listing arrangement by appropriate proportion.; the completedness of the objects was expressed by the stationary state where overall image is fixed, the construction of homogeneous and complete space, and absolute inevitability of internal layout in proportion; lastly, organic harmony of independent parts was stressed in independent completedness of each detail, and organic harmony of the whole. The expressive features would lead to a unique expression style of linear emphasis, proportion, constructive forms, and two-dimensional arrangement. The meaning of this study is follows: The characteristics of art school of thought are given shape by appling & analysing the architectural layout principles of historical art school of thought to modern fashion in the view point of formal construction dimension. The applied possibility of historical art school of thought as the source of inspiration about the fashion design is extended.

Response Analysis of Nearby Structures with the Consideration of Tunnel Construction and Ground Conditions (터널시공 및 지반조건을 반영한 인접구조물의 거동분석)

  • Son, Moorak;Yun, Jongcheol
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.6C
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    • pp.255-263
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    • 2010
  • This paper investigates the effects of tunnelling-induced ground movements on nearby structures, considering soil-structure interactions of different construction (ground loss) and soil characteristics. The response of four-story block structures, which are subjected to tunnelling-induced ground movements, has been investigated in different construction (ground loss) and soil conditions using numerical analysis. The structures for numerical analysis has been modelled using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four-story block structures has been investigated with a ground movement magnitude and compared in terms of construction (ground loss) and soil conditions considering the magnitude of deformations and cracks in structures. In addition, the damage levels, which are possibly induced in structures, has been provided in terms of construction (ground loss) and soil conditions using the state of strain damage estimation criterion (Son and Cording, 2005). The results of this study will provide a background for better understandings for controlling and minimizing building damage on nearby structures due to tunnelling-induced ground movements.

Measurement of Mechanical and Physical Properties of Pepper for Particle Behavior Analysis

  • Nam, Ju-Seok;Byun, Jun-Hee;Kim, Tae-Hyeong;Kim, Myoung-Ho;Kim, Dae-Cheol
    • Journal of Biosystems Engineering
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    • v.43 no.3
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    • pp.173-184
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    • 2018
  • Purpose: This study was conducted to investigate the mechanical and physical properties of a Korean red pepper variety for particle behavior analysis. Methods: Poisson's ratio, modulus of elasticity, shear modulus, density, coefficient of restitution, and coefficient of friction were derived for "AR Legend," which is a domestic pepper variety. The modulus of elasticity and Poisson's ratio were measured through a compression test using a texture analyzer. The shear modulus was calculated from the modulus of elasticity and Poisson's ratio. The density was measured using a water pycnometer method. The coefficient of restitution was measured using a collision test, and the static and dynamic friction coefficients were measured using a inclined plane test. Each test was repeated 3-5 times except for density measurement, and the results were analyzed using mean values. Results: Poisson's ratios for the pepper fruit and pepper stem were 0.295 and 0.291, respectively. Elastic moduli of the pepper fruit and pepper stem were $1.152{\times}10^7Pa$ and $3.295{\times}10^7Pa$, respectively, and the shear moduli of the pepper fruit and pepper stem were $4.624{\times}10^6Pa$ and $1.276{\times}10^7Pa$, respectively. The density of the pepper fruit and the pepper stem were $601.8kg/m^3$ and $980.4kg/m^3$, respectively. The restitution coefficients between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.383, 0.218, 0.277, 0.399, and 0.148, respectively. The coefficients of static friction between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.455, 0.332, 0.306, 0.364, and 0.404, respectively. The coefficients of dynamic friction between a pepper fruit and plastic and a pepper stem and plastic were 0.043 and 0.034, respectively.

Review on Discontinuum-based Coupled Hydro-Mechanical Analyses for Modelling a Deep Geological Repository for High-Level Radioactive Waste (고준위방사성폐기물 심층처분장 모델링을 위한 불연속체 기반 수리-역학 복합거동 해석기법 현황 분석)

  • Kwon, Saeha;Kim, Kwang-Il;Lee, Changsoo;Kim, Jin-Seop;Min, Ki-Bok
    • Tunnel and Underground Space
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    • v.31 no.5
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    • pp.309-332
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    • 2021
  • Natural barrier systems surrounding the geological repository for the high-level radioactive waste should guarantee the hydraulic performance for preventing or delaying the leakage of radionuclide. In the case of the behavior of a crystalline rock, the hydraulic performance tends to be decided by the existence of discontinuities, so the coupled hydro-mechanical(HM) processes on the discontinuities should be characterized. The discontinuum modelling can describe the complicated behavior of discontinuities including creation, propagation, deformation and slip, so it is appropriate to model the behavior of a crystalline rock. This paper investigated the coupled HM processes in discontinuum modelling such as UDEC, 3DEC, PFC, DDA, FRACOD and TOUGH-UDEC. Block-based discontinuum methods tend to describe the HM processes based on the fluid flow through the discontinuities, and some methods are combined with another numerical tool specialized in hydraulic analysis. Particle-based discontinuum modelling describes the overall HM processes based on the fluid flow among the particles. The discontinuum methods that are currently available have limitations: exclusive simulations for two-dimension, low hydraulic simulation efficiency, fracture-dominated fluid flow and simplified hydraulic analysis, so it could be improper to the modelling the geological repository. Based on the concepts of various discontinuum modelling compiled in this paper, the advanced numerical tools for describing the accurate coupled HM processes of the deep geological repository should be developed.

Numerical analysis on the estimation of optimal disc cutter angle in transition cutter zone (전이 구간(트렌지션 커터존)의 최적 디스크커터 각도 산정에 관한 수치해석 연구)

  • Lee, Sang Yun;Song, Ki-il
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.23 no.1
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    • pp.1-12
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    • 2021
  • In the design of a tunnel boring machine (TBM), the excavation efficiency of the equipment depends on the design of the cutter head, which is directly in contact with the ground. Especially, the allocation of disc cutter is crucial issue. Disc cutters can be divided into center cutter zone, inner cutter zone and transition cutter zone depending on where they are placed. Many studies have been conducted to identify optimal cutting conditions for face cutters. However, research to determine the optimal cutting conditions for the transition cutter has been relatively incomplete. In this study, to identify the optimal cutting conditions for the transition cutter, numerical analysis using discrete element method was performed, and the specific energy curve according to the angle between the transition cutters was drawn to find out the optimum cutting conditions. The results show that the angle between the transition cutters showing minimum specific energy in the transition cutter zone is 9°. Transition cutter zone was divided into three sections according to the slope angle of the transition cutter. It is also found that, the greater the slope angle of the transition cutter. This finding shows good agreement with the present design of transition cutter zone.

Simulation analysis and evaluation of decontamination effect of different abrasive jet process parameters on radioactively contaminated metal

  • Lin Zhong;Jian Deng;Zhe-wen Zuo;Can-yu Huang;Bo Chen;Lin Lei;Ze-yong Lei;Jie-heng Lei;Mu Zhao;Yun-fei Hua
    • Nuclear Engineering and Technology
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    • v.55 no.11
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    • pp.3940-3955
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    • 2023
  • A new method of numerical simulating prediction and decontamination effect evaluation for abrasive jet decontamination to radioactively contaminated metal is proposed. Based on the Computational Fluid Dynamics and Discrete Element Model (CFD-DEM) coupled simulation model, the motion patterns and distribution of abrasives can be predicted, and the decontamination effect can be evaluated by image processing and recognition technology. The impact of three key parameters (impact distance, inlet pressure, abrasive mass flow rate) on the decontamination effect is revealed. Moreover, here are experiments of reliability verification to decontamination effect and numerical simulation methods that has been conducted. The results show that: 60Co and other homogeneous solid solution radioactive pollutants can be removed by abrasive jet, and the average removal rate of Co exceeds 80%. It is reliable for the proposed numerical simulation and evaluation method because of the well goodness of fit between predicted value and actual values: The predicted values and actual values of the abrasive distribution diameter are Ф57 and Ф55; the total coverage rate is 26.42% and 23.50%; the average impact velocity is 81.73 m/s and 78.00 m/s. Further analysis shows that the impact distance has a significant impact on the distribution of abrasive particles on the target surface, the coverage rate of the core area increases at first, and then decreases with the increase of the impact distance of the nozzle, which reach a maximum of 14.44% at 300 mm. It is recommended to set the impact distance around 300 mm, because at this time the core area coverage of the abrasive is the largest and the impact velocity is stable at the highest speed of 81.94 m/s. The impact of the nozzle inlet pressure on the decontamination effect mainly affects the impact kinetic energy of the abrasive and has little impact on the distribution. The greater the inlet pressure, the greater the impact kinetic energy, and the stronger the decontamination ability of the abrasive. But in return, the energy consumption is higher, too. For the decontamination of radioactively contaminated metals, it is recommended to set the inlet pressure of the nozzle at around 0.6 MPa. Because most of the Co elements can be removed under this pressure. Increasing the mass and flow of abrasives appropriately can enhance the decontamination effectiveness. The total mass of abrasives per unit decontamination area is suggested to be 50 g because the core area coverage rate of the abrasive is relatively large under this condition; and the nozzle wear extent is acceptable.