• Title/Summary/Keyword: Tunnel numerical analysis

Search Result 1,159, Processing Time 0.023 seconds

Stability Analysis of Multiple Thermal Energy Storage Caverns Using a Coupled Thermal-Mechanical Model (열-역학적 연계해석 모델을 이용한 다중 열저장공동 안정성 분석)

  • Kim, Hyunwoo;Park, Dohyun;Park, Eui-Seob;Sunwoo, Choon
    • Tunnel and Underground Space
    • /
    • v.24 no.4
    • /
    • pp.297-307
    • /
    • 2014
  • Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injection-and-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in $FLAC^{3D}$. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.

Statistical Analysis of Geometric Parameters and Rock Conditions of Pick Cutters for Roadheaders (로드헤더용 픽커터의 형상변수와 암반조건에 대한 통계적 분석)

  • Soo-Ho Chang;Tae-Ho Kang;Chulho Lee;Soon-Wook Choi
    • Tunnel and Underground Space
    • /
    • v.33 no.5
    • /
    • pp.414-424
    • /
    • 2023
  • In this study, a total of 326 data on a variety of geometric parameters of pick cutters and the corresponding cuttable rock conditions were collected and built as a database. Statistical analysis of the database showed that there is a significant positive correlation between the parameters that define the geometry of a pick cutter, especially between the parameters related to the length of a pick cutter and the geometry of a tungsten carbide insert. The diameter of a pick cutter shaft was also strongly correlated with the geometry of the inserts. On the other hand, it was difficult to find a clear correlation between the parameters for the rock conditions defined by the four conditions and the geometric parameters of pick cutters, which may be due to the uncertainty of the rock mass and the fact that the application of a pick cutter is presented as a range rather than a numerical single value. However, the mean values of geometric parameters of pick cutters tend to increase as a rock mass becomes harder. However, the pick length parameters are found to decrease as a rock mass becomes harder, which may be a way to reduce the moments that can occur when using long pick cutters in a hard rock condition.

Analysis of Nonlinear Behaviors of Shotcrete-Steel Support Lining Considering the Axial Force Effects (축력의 영향을 고려한 숏크리트-강지보 합성 라이닝의 비선형 거동 분석)

  • Yu, Jeehwan;Kim, Jeongsoo;Kim, Moon Kyum
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.37 no.2
    • /
    • pp.357-367
    • /
    • 2017
  • Bending and axial forces simultaneously occur at the cross-section of a shotcrete lining reinforced with steel supports due to the tunnel geometry. The shotcrete has changing flexural stiffness depending on the axial forces and, as a result, severely nonlinear behavior. The mechanical properties of a shotcrete-steel composite also depend on the type of steel support. This study presents a fiber section element model considering the effect of axial force to evaluate the nonlinear behavior of a shotcrete-steel composite. Additionally, the model was used to analyze the effects of different types of steel supports on the load capacity. Furthermore, a modified hyperbolic model for ground reaction, including strain-softening, is proposed to account for the ground-lining interaction. The model was validated by comparing the numerical results with results from previous load test performed on arched shotcrete specimens. The changes in mechanical responses of the lining were also investigated. Results show a lining with doubly reinforcement rebar has similar load capacity as a lining with H-shaped supports. The use of more materials for the steel support enhances the residual resistance. For all types of steel reinforcement, the contribution of steel supports during peak load decreases as the ground becomes stiffer.

Thermal Performance Analysis of Multiple Thermal Energy Storage (TES) Caverns with Different Separation Distances Using Computational Fluid Dynamics (전산유체역학을 이용한 다중 열저장공동의 이격거리별 열적 성능 분석)

  • Park, Dohyun;Park, Eui-Seob;Sunwoo, Choon
    • Tunnel and Underground Space
    • /
    • v.24 no.3
    • /
    • pp.201-211
    • /
    • 2014
  • In the present study, the thermal performance of multiple rock caverns for large-scale thermal energy storage (TES) was numerically investigated for different separation distances between the caverns through heat transfer analysis using a computational fluid dynamics code, FLUENT. The thermal performance of multiple caverns was assessed in terms of the thermal stratification within the caverns and the heat loss to the surroundings, and the heating characteristics of the rock around the caverns were investigated. The results of numerical simulation showed that there was little difference in thermal performance between multiple TES caverns with different separation distances when the surrounding rock was less heated and it reached thermal steady-state, which represent the thermal states of the surrounding rock at the early and long-term operational stages of the TES caverns, respectively. However, as the separation distance decreased, the rock between the caverns reached thermal steady-state more quickly, and thus the heat loss from the caverns tended to converge rapidly to the value of heat loss occurred under thermal steady-state conditions in the surrounding rock. This result implies that the operating cost of heating the surrounding rock (i.e., rock heating) can be reduced with a reduction in the separation distance between multiple caverns, and suggests that the separation distance should be determined by considering the operating cost of rock heating as well as the construction cost of the caverns.

Numerical Analysis of the Visco-plastic Behavior of Rock Mass Considering Continuum Joints and Rock Bolt Elements (연속체 절리와 록볼트 요소를 고려한 암반의 점소성 거동에 관한 수치해석)

  • 노승환;이정인;이연규
    • Tunnel and Underground Space
    • /
    • v.14 no.3
    • /
    • pp.215-228
    • /
    • 2004
  • Rock mass contains discontinuities such as faults and joints, and their mechanical properties and spatial distribution dominate the stability of rock mass. Because the deformation of rock mass occurs discontinuities in many cases. However in the case of poor quality rock mass under high stresses, the deformation along intact rock can also influence the structure's stability. In this study, two dimensional finite element program was developed with a rheological model to analyze the stability of the structure excavated in jointed rock mass. The “equivalent material” approach was used assuming intact rock, joints and rock bolts as visco-plastic materials. The program was verified by analysing an intact rock model, a jointed rock mass model and a reinforced jointed rock mass model. The displacement was examined in each model with changing the intact rock behaviour as elastic and visco-plastic. In the case of poor quality rock mass under high stresses, e assumption of visco-plastic behaviour of intact rock resulted in larger displacement than when assuming elastic behaviour for intact rock. Therefore it is recommended to add intact rock's visco-plastic behaviour to the existing model, which only assumes visco-plastic behaviour of joints and rock bolts.

A Study on Mine Ventilation Network (광산 통기 네트워크 연구)

  • Kim, Soo Hong;Kim, Yun Kwang;Kim, Sun Myung;Jang, Yun Ho
    • Tunnel and Underground Space
    • /
    • v.27 no.4
    • /
    • pp.217-229
    • /
    • 2017
  • This study focuses on the improvement of the working environment in domestic collieries where temperature is increasing due to heat of the earth that is caused by the long-term mining. In order to improve the working environment of the mine, a ventilation evaluation was carried out for Hwasoon Mining Industry. In order to increase the ventilation efficiency of the mine, numerical analysis of the effect on temperature was carried out by using climsim, a temperature prediction program. The analysis shows that A coal mine needs $6,152m^3/min$ for in-flow ventilation rate but the total input air flowrate is $4,710m^3/min$, $1,442m^3/min$ of in-flow ventilation rate shortage. The 93 m hypothetical ventilation shaft from -395 ML to -488 ML could result about $3^{\circ}C$ temperature drop in the coal mine of -488 ML far. As a result of predicting the $CO_2$ concentration at -523 ML development using artificial neural network, the emission of $CO_2$ increased as the amount of coal and coal bed thickness increased. The factors that have the greatest effect on the amount of $CO_2$ emissions were coal layer thickness and coal mining. And, as the air quantity increases, it has a great effect on the decrease of carbon dioxide concentration.

Effects of types of bridge decks on competitive relationships between aerostatic and flutter stability for a super long cable-stayed bridge

  • Hu, Chuanxin;Zhou, Zhiyong;Jiang, Baosong
    • Wind and Structures
    • /
    • v.28 no.4
    • /
    • pp.255-270
    • /
    • 2019
  • Aerodynamic configurations of bridge decks have significant effects on the aerostatic torsional divergence and flutter forsuper long-span bridges, which are onset for selection of suitable bridge decksfor those bridges. Based on a cable-stayed bridge with double main spans of 1500 m, considering typical twin-box, stiffening truss and closed-box section, which are the most commonly used form of bridge decks and assumed that the rigidity of those section is completely equivalent, are utilized to investigate the effects of aerodynamic configurations of bridge decks on aerodynamic instability performance comprised of the aerostatic torsional divergence and flutter, by means of wind tunnel tests and numerical calculations, including three-dimensional (3D) multimode flutter analysis and nonlinear aerostatic analysis. Regarding the aerostatic torsional divergence, the results obtained in this study show twin-box section is the best, closed-box section the second-best, and the stiffening truss section the worst. Regarding the flutter, the flutter stability of the twin-box section is far better than that of the stiffening truss and closed-box section. Furthermore, wind-resistance design depends on the torsional divergence for the twin-box and stiffening truss section. However, there are obvious competitive relationships between the aerostatic torsional divergence and flutter for the closed-box section. Flutter occur before aerostatic instability at initial attack angle of $+3^{\circ}$ and $0^{\circ}$, while the aerostatic torsional divergence occur before flutter at initial attack angle of $-3^{\circ}$. The twin-box section is the best in terms of both aerostatic and flutter stability among those bridge decks. Then mechanisms of aerostatic torsional divergence are revealed by tracking the cable forces synchronous with deformation of the bridge decksin the instability process. It was also found that the onset wind velocities of these bridge decks are very similar at attack angle of $-3^{\circ}$. This indicatesthat a stable triangular structure made up of the cable planes, the tower, and the bridge deck greatly improves the aerostatic stability of the structure, while the aerodynamic effects associated with the aerodynamic configurations of the bridge decks have little effects on the aerostatic stability at initial attack angle of $-3^{\circ}$. In addition, instability patterns of the bridge depend on both the initial attack angles and aerodynamic configurations of the bridge decks. This study is helpful in determining bridge decksfor super long-span bridges in future.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.27 no.7
    • /
    • pp.380-394
    • /
    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

A study on the applicability of under ground structure using steel tubular roof in Korean geotechnical condition (대구경강관을 이용한 지하구조물 축조공법의 국내지반 적용성 연구)

  • Lee, Young-Bock;Kim, Jeong-Yoon;Park, Inn-Joon;Kim, Kyong-Gon;Lee, Jong-Ho
    • Journal of Korean Tunnelling and Underground Space Association
    • /
    • v.5 no.4
    • /
    • pp.401-409
    • /
    • 2003
  • Recently, the development of underground structures is to be inevitably necessary due to the increase in population and traffic volume that has caused to the limit of urban land use and the heavy traffic jams. Therefore, underground structures such as subway, underground shopping centers, lifeline facilities and so on, have been increasingly constructed, On the other hand, several social problems have occurred during construction, i.e., ground subsidence, noise, and vibration. Therefore, safer and more beneficial methods for underground construction are on the demand. In this research, N.T.R.(New Tubular Roof) method has been modified and utilized for solving those problems and overcoming the difficulties connected with the bored tunnel construction of large underground openings in unfavorable ground, often under the water table, and with overburdens that are too shallow to solve problems of stability using traditional methods. The N.T.R. method has been modified to suit for Korean geotechnical conditions, and was made up for the weak points-the water leakage from walls and tops, the maintenance and the lack of stability-of the conventional methods. This paper dealt with the features and the applicability of N.T.R. Method based on the results from numerical analysis and data from in-situ monitoring system.

  • PDF

A Study of Torsional Vibrations of Suspended Bridges (현수교(懸垂橋)의 비틀림진동(振動)에 관한 연구(硏究))

  • Min, Chang Shik;Kim, Saeng Bin;Son, Seong Yo
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.3 no.3
    • /
    • pp.27-37
    • /
    • 1983
  • A method of dynamic analysis is developed for torsional free vibrations of elliptical-box girder type or stiffening truss system suspension bridge. In this study, the method based on a finite element technique using a digital computer, is illustrated by two numerical examples, the Namhae Bridge which is located in Kyungsang nam-do opened on June, 1973, and the Mt. Chunma Bridge is simple span pedestrian's suspension bridge with lateral bracing system in Mt. Chunma, Kyungki-do, are used. In general, dynamic modes of complex suspension bridges are three-dimensional in form, i.e., coupling between vertical and torsional motions. However, introduced that amplitudes of oscillation are infinitesimal for coincidence with the purpose of it's use, thereupon, the torsional vibration analyses are treated without coupling terms. A sufficient number of natural frequencies and mode shapes for torsional free vibration are presented in this paper. In the case of Mt. Chunma Bridge, the natural frequencies and periods are computed with and without reinforcement, respectively, and compared their discrepancies. The influence of the auxiliary reinforcing cables is prevailing in the first few modes, namely, 1st and 2nd in symmetric and 1st, 2nd and 3rd in antisymmetric vibration, and conspicuous in the symmetric compared with the antisymmetric motion, but in the higher modes, this kind of simple accessory elucidates rether converse effects. In the Namhae Bridge, the results are compared with the Manual's obtained by wind tunnel test. It reveals commendable agreement.

  • PDF