• Title/Summary/Keyword: tunnel support

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Application of New Type Accelerator for High Quality Shotcrete (고품질 숏크리트 개발을 위한 새로운 급결제 적용)

  • Park, Hae-Geun;Lee, Myeong-Sub;Kim, Jea-Kwon;Jung, Myung-Keun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.1
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    • pp.45-55
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    • 2002
  • From the early 1980's, the New Austrian Tunnelling Method (NATM) has been developed as one of the standard tunnelling methods in Korea. Approximately 10 years ago, wet-mix shotcrete with sodium silicate (waterglass) accelerator was introduced and widely used to tunnel lining and underground support. However, this accelerator had some disadvantages due to the decrease of long-term strength compared to plain concrete (without accelerator) and low quality of the hardened shotcrete. In order to compensate for these disadvantages, recently developed alkali-free accelerator has been successfully demonstrated in numerous projects and applications as a new material to make tunnels more durable and safer. An experimental investigation was carried out in order to verify the strength behavior of wet-mix Steel Fiber Reinforced Shotcrete (SFRS) with alkali-free accelerator. Compressive strength, flexural strength, and flexural toughness were measured by testing specimens extracted from the shotcrete panels. From the results, wet-mix SFRS with alkali-free accelerator exhibited excellent strength improvement compared to the conventional shotcrete accelerator.

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Quantitative assessment of depth and extent of notch brittle failure in deep tunneling using inferential statistical analysis

  • Lee, Kang-Hyun;Lee, In-Mo;Shin, Young-Jin
    • Geomechanics and Engineering
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    • v.21 no.2
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    • pp.201-206
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    • 2020
  • A stress-induced brittle failure in deep tunneling generates spalling and slabbing, eventually causing a v-shaped notch formation. An empirical relationship for the depth of the notch to the maximum tangential stress assuming an equivalent circular cross-section was proposed (Martin et al. 1999). While this empirical approach has been well recognized in the industry and used as a design guideline in many projects, its applicability to a non-circular opening is worth revisiting due to the use of equivalent circular profile. Moreover, even though the extent of the notch also contributes to notch failure, it has not been estimated to date. When the estimate of both the depth and the extent of notch are combined, a practical and economically justifiable support design can be achieved. In this study, a new methodology to assess the depth as well as the extent of notch failure is developed. Field data and numerical simulations using the Cohesion Weakening Frictional Strengthening (CWFS) model were collected and correlated with the three most commonly accepted failure criteria (σ13, Dismaxc, σdevcm). For the numerical analyses, the D-shaped tunnel was used since most civil tunnels are built to this profile. Inferential statistical analysis is applied to predict the failure range with a 95% confidence level. Considering its accuracy and simplicity, the new correlation can be used as an enhanced version of failure assessment.

Calibration System for Three-Cup Anemometers (현장용 교정 장치를 이용한 3-컵 풍속계의 교정 방법)

  • Chun, Se-Jong;Lee, Saeng-Hee;Choi, Yong-Moon
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.34 no.3
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    • pp.325-331
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    • 2010
  • Three-cup anemometers are popular devices for measuring wind speeds in automated weather stations, environmental monitoring systems, and wind turbines. Cup anemometers usually suffer from lack of long-term stability owing to the wear of the bearing systems that support the rotational parts. The bearing systems are susceptible to external pollutants, vibrations, and gusts. Therefore, these anemometers have to be calibrated regularly to maintain the desired characteristics for measuring wind speed. In the present study, a new in-situ calibration system to help reduce cost and save time by calibrating the cup anemometers at the installation site is proposed. A portable in-situ calibrator was fabricated. After the characteristics of this calibrator were verified, it was used to calibrate cup anemometers. Some of the calibration results were compared with the data obtained by wind tunnel testing.

Leveraging Proxy Mobile IPv6 with SDN

  • Raza, Syed M.;Kim, Dongsoo S.;Shin, DongRyeol;Choo, Hyunseung
    • Journal of Communications and Networks
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    • v.18 no.3
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    • pp.460-475
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    • 2016
  • The existing Proxy Mobile IPv6 suffers from a long handover latency which in turn causes significant packet loss that is unacceptable for seamless realtime services such as multimedia streaming. This paper proposes an OpenFlow-enabled proxy mobile IPv6 (OF-PMIPv6) in which the control of access gateways is centralized at an OpenFlow controller of a foreign network. The proposed OF-PMIPv6 separates the control path from the data path by performing the mobility control at the controller, whereas the data path remains direct between a mobile access gateway and a local mobility anchor in an IP tunnel form. A group of simple OpenFlow-enabled access gateways performs link-layer control and monitoring activities to support a comprehensive mobility of mobile nodes, and communicates with the controller through the standard OpenFlow protocol. The controller performs network-layer mobility control on behalf of mobile access gateways and communicates with the local mobility anchor in the Proxy Mobile IPv6 domain. Benefiting from the centralized view and information, the controller caches the authentication and configuration information and reuses it to significantly reduce the handover latency. An analytical analysis of the proposed OF-PMIPv6 reactive and proactive handover schemes shows 43% and 121% reduction in the handover latency, respectively, for highly utilized network. The results gathered from the OF-PMIPv6 testbed suggest similar performance improvements.

Performance Evaluation of Improved Fast PMIPv6-Based Network Mobility for Intelligent Transportation Systems

  • Ryu, Seonggeun;Choi, Ji-Woong;Park, Kyung-Joon
    • Journal of Communications and Networks
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    • v.15 no.2
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    • pp.142-152
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    • 2013
  • The network mobility basic support (NEMO BS) protocol has been investigated to provide Internet connectivity for a group of nodes, which is suitable for intelligent transportation systems (ITS) applications. NEMO BS often increases the traffic load and handover latency because it is designed on the basis of mobile Internet protocol version 6 (MIPv6). Therefore, schemes combining proxy MIPv6 with NEMO (P-NEMO) have emerged to solve these problems. However, these schemes still suffer from packet loss and long handover latency during handover. Fast P-NEMO (FP-NEMO) has emerged to prevent these problems. Although the FP-NEMO accelerates handover, it can cause a serious tunneling burden between the mobile access gateways (MAGs) during handover. This problem becomes more critical as the traffic between the MAGs increases. Therefore, we propose a scheme for designing an improved FP-NEMO (IFP-NEMO) to eliminate the tunneling burden by registering a new address in advance. When the registration is completed before the layer 2 handover, the packets are forwarded to the new MAG directly and thereby the IFP-NEMO avoids the use of the tunnel between the MAGs during handover. For the evaluation of the performance of the IFP-NEMO compared with the FP-NEMO, we develop an analytical framework for fast handovers on the basis of P-NEMO. Finally, we demonstrate that the IFP-NEMO outperforms the FP-NEMO through numerical results.

Design and Performance Analysis of Propeller for Solar-powered HALE UAV EAV-3 (고고도 장기체공 태양광 무인기 EAV-3의 프로펠러 설계 및 성능해석)

  • Park, Donghun;Hwang, Seungjae;Kim, Sanggon;Kim, Cheolwan;Lee, Yunggyo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.44 no.9
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    • pp.759-768
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    • 2016
  • Design and performance analysis of propeller for solar-powered HALE UAV, EAV-3 are conducted. Experiment points of design variables are obtained by using Design of Experiment(DOE) and Kriging meta-model is generated for objective and constraints function. The geometry of propeller is designed by evaluating the response surface with requirement and restrictions. The validity of the design is verified by meta-model based optimization. Computational analyses are carried out by using commercial CFD code and the results are compared with those from a design code and wind tunnel test. The results showed good agreement with predictions of the design code at the design altitude. Also, it is confirmed that the blockage effect due to the measurement device and support strut is included in the test data and the results including this effect compare well with the test data.

An Implementation of Explicit Multicast with Mobile IP for Small Group Communications in Mobile Networks (이동통신환경에서의 소규모 그룹통신을 위한 XMIP 프로토콜의 구현)

  • PARK IN-SOO;PARK YONG-JIN
    • The KIPS Transactions:PartC
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    • v.12C no.2 s.98
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    • pp.267-280
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    • 2005
  • In this paper, we implement and verify XMIP integrating IETF Mobile IP and the Explicit Multicast mechanism for a great number of small group multicast communications. U a source node sends Xcast packets explicitly inserting destination nodes into the headers, each Xcast router decides routes and forwards the packets toward each destination node based on unicast routing table without the support of multicast trees. n is a straightforward and simple multicast mechanism just based on a unicast routing table without maintaining multicast states because of the inheritance from the Explicit Multicast mechanism. This research modifies and extends the functionality of IETF Mobile IP's mobility agents, such as HA/FA to HA+/FA+ respectively, considering interworking with Xcast networks. Xcast packets captured by HA+ are forwarded into X-in-X tunnel interfaces for each FA+ referred to the binding table of HA.. This X-in-X tunneling mechanism can effectively solve the traffic concentration problem of IETF Mobile IP multicast services. Finally WLAN-based testbed is built and a multi-user Instant messenger system is developed as a Xcast application for finally verify the feasibility of the implemented XMIP/Xcast protocols.

Case Study on In-situ Stress Measurement by Over-coring and Its Application to Design of a Pumped Storage Power Plant (오버코어링법에 의한 초기지압측정 및 양수발전소 설계적용사례)

  • Kim, Dae-Young;Lee, Hong-Sung;Lee, Young-Nam
    • Tunnel and Underground Space
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    • v.17 no.2 s.67
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    • pp.90-101
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    • 2007
  • With increasing development of underground space, underground pumped storage power plants, which generate power by felling water in upper reservoir to lower reservoir, have been continuously constructed. For efficient and safe design, construction and maintenance or such power plants, it is very important to understand in-situ stress and the mechanical properties of the surrounding rock mass at the design stage. The power plant presented in this paper is under construction at a depth of $320{\sim}375m$. For stability evaluation of the structure, in-situ stress was measured by over-coring method. Also pressurementer test and a series or laboratory tests were performed to obtain the mechanical properties. Numerical analyses were conducted to check the efficiency of designed support patterns. The results showed that unstable areas occurred partly in the numerical model, and therefore supports were additionally applied. Finally complete stability was obtained and the following excavation has been operated successfully until now.

A Study on Optimal Technical Factors of USFSS Based on Integrated Technique of Wireless Communication and Location Awareness (무선통신 및 위치인식 통합기술을 활용한 지하구조물 현장지원시스템 최적 요소기술 연구)

  • Jang, Yong-Gu;Jeong, Jae-Hyung;Lee, Jun-Woo;Kim, Hyun-Soo
    • Journal of the Korean Association of Geographic Information Studies
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    • v.12 no.4
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    • pp.48-58
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    • 2009
  • In recent years, construction worker safety in construction site is important. Especially, the frequent collapse accidents have happened in tunnels, utility tunnel and underground structure, so that the importance of worker safety is greatly emphasized. It is difficult to communicate with other workers in underground space, using the current cable or wireless communicator. When the accident is occurred, it can't rescue workers. This is the reason that it has a deficiency to find a location of survivor and communicate rescure crew and field workers. In this paper we extract the optimal technical factors of USFSS(Underground Structure Field Support System) based on integrated technique of wireless communication and location awareness. And USFSS developed in this study is suited for bad environment of underground structure construction and able to track 3D position of laborer and communicate mutually.

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Effect of trailing-edge modification over aerodynamic characteristics of NACA 0020 airfoil

  • Ethiraj, Livya;Pillai, Subramania Nadaraja
    • Wind and Structures
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    • v.33 no.6
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    • pp.463-470
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    • 2021
  • This study investigates the aerodynamic characteristics of NACA series airfoil by altering the trailing edge in the form of extended and serrated sections. This contemporary advent examined NACA 0020 airfoil experimentally at the angle of attack ranging from 0° to 45° and for the Reynolds number of 2.46 × 105. To figure out the flow behaviour, the standard average pressure distribution over the airfoil surface is estimated with 50 pressure taps. The time series surface pressure is recorded for 700 Hz of sampling frequency. The extended trailing edge of 0.1 c, 0.2 c and 0.3 c are attached to the base airfoil. Further, the triangular serration is introduced with the base length of 2 cm, 4 cm and 6 cm. Each base length with three different amplitudes of 0.1 c, 0.2 c and 0.3 c were designed and equipped with the baseline case at the trailing edge and tested. The aerodynamic force coefficient, as well as pressure coefficient are presented. The obtained data advises that modification in the trailing edge will reflect the aerodynamic characteristics and the flow behaviour over the section of a wing. Resultantly, the extended trailing edge as a thin elongated surface attached to a base airfoil without revising the main airfoil favors good lift increment. The serrated trailing edge acts as a flow control device by altering the flow pattern results to delay the stall phenomenon. Besides it, improves lift co-efficient with less amount of additional drag. This extended and serrated trailing edge approach can support for designing the future smart airfoil.