• Title/Summary/Keyword: Ground fault

Search Result 738, Processing Time 0.034 seconds

The Prediction of Ground Condition ahead of the Tunnel Face using 3-Dimensional Numerical Analysis (3차원 수치해석을 이용한 터널막장 전방 지반 상태의 예측)

  • You Kwang-Ho;Song Han-Chan;Kim Ki-Sun;Lee Dae-Hyuck;Park Yeon-Jun
    • Tunnel and Underground Space
    • /
    • v.14 no.6 s.53
    • /
    • pp.440-449
    • /
    • 2004
  • Rock mass includes natural discontinuities such as joints and faults during its formation. Discontinuities are also referred as planes of weakness because of their weak mechanical characteristics. In the design of underground structures, it is necessary to consider the properties of discontinuities to insure the stability. During the excavation of a tunnel, these discontinuities have to be identified as early as possible so that proper change in excavation method or support design can be made accordingly. The excavation of the tunnel in a stable rock mass causes a 3-dimensional arching effect around the excavation face. It was revealed by previous studies that the existence of a weak zone or a fault zone ahead of tunnel foe induces a typical displacement tendency of convergence. For better understanding of the meaning of influence/trend lines of various displacement components, three-dimensional numerical analyses were conducted while varying deformation moduli, thicknesses and orientations of discontinuities. Numerical results showed that the changes in influence/trend lines of various displacement components were very similar to those by measurements. The discrepancies from the expected values were dependent on the physical properties, thicknesses and orientations of discontinuities.

A Case Studty on the Ground Reinforcement and Waterproofing Effect of Weathering and Fault Zone by Special Injection Tip Equipment Using Microcement Type (특수주입선단장치에 의한 마이크로시멘트계 약액주입의 풍화대, 단층파쇄대의 지반보강 및 차수효과 사례연구)

  • Do, Jongnam;Jung, Jongju;Chun, Byungsik
    • Journal of the Korean GEO-environmental Society
    • /
    • v.10 no.2
    • /
    • pp.21-28
    • /
    • 2009
  • A grouting method has been widely used in construction of large-scale structure to reduce permeability and reinforce the ground. If cement and grout material were not mixed well in the injection tip equipment, an opposite flow and interception state of the chemical grouting can occur. McG (Multi-mixing counterflow prevented Grouting, McG) method installed a special grouting device to allow better mixing of the grouting material(above fineness $6,000cm^2/g$) and prevent backward flow. The block of nozzle also diversify powder rate of cement. YSS (Youngil Special Silicate, YSS) that lowers $Na_2O$ and thereby increases durability was developed by gel-forming reaction material. The seepage state and unconfined compressive strength of the injection material using the special injection tip equipment was tested in this study. The results of this study showed that the uniaxial compressive strength, permeability, N-value, TCR and RQD were improved by this method. Engineering characteristics obtained by the special injection tip method will be compared with those by the other method through various field tests from now on.

  • PDF

Seismic Behavior and Estimation for Base Isolator Bearings with Self-centering and Reinforcing Systems (자동복원 및 보강 시스템과 결합된 면진받침의 지진거동과 평가)

  • Hu, Jong Wan
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.35 no.5
    • /
    • pp.1025-1037
    • /
    • 2015
  • Flexible base isolation bearings that separate superstructure from ground have been widely used in the construction field because they make a significant contribution to increasing the fundamental period of the structure, thereby decreasing response acceleration transmitted into the superstructure. However, the established bearing devices installed to uphold the whole building give rise to some problems involved with failure and collapse due to lack of the capacity as modern structures are getting more massive and higher. Therefore, this study suggests new isolation bearings assembled with additional restrainers enabled to reinforcing and recentering, and then evaluates their performance to withstand the seismic load. The superelastic shape memory alloy (SMA) bars are installed into the conventional lead-rubber bearing (LRB) devices in order to provide recentering forces. These new systems are modeled as component spring models for the purpose of conducting nonlinear dynamic analyses with near fault ground motion data. The LRB devices with steel bars are also designed and analyzed to compare their responses with those of new systems. After numerical analyses, ultimate strength, maximum displacement, permanent deformation, and recentering ratio are compared to each model with an aim to investigate which base isolation models are superior. It can be shown that LRB models with superelastic SMA bars are superior to other models compared to each other in terms of seismic resistance and recentering effect.

Damping Analysis using IEEEST PSS and PSS2A PSS

  • Lee Sang-Seung;Kang Sang-Hee;Jang Gwang-Soo;Li Shan-Ying;Park Jong-Keun;Moon Seung-Il;Yoon Yong-Tae
    • Journal of Electrical Engineering and Technology
    • /
    • v.1 no.3
    • /
    • pp.271-278
    • /
    • 2006
  • This paper scrutinized the damping effects of installing the prototype PSSs by a transient analysis for eight buses of faults in the South Korean power system. The PSSs used have the co-PSS blocks for IEEEST model with a single input and the co+power PSS blocks for PSS2A model with dual inputs. The simulation tool was a TSAT(Transient Security Assessment Tool) developed by Powertech Labs Inc. The voltages of the transmission line for simulations were 765kV and 345kV, and the faults for eight cases were sequenced by considering the open state and the close state of the lines. In the simulations, the three-phase line to ground (L-G) fault generated different points for each region. The simulations were compared to the cases of no PSS, partial IEEEST and PSS2A, absolute IEEEST, and absolute PSS2A to show that the power system oscillation can be effectively damped by PSS modules. Simulations were conducted to confirm the effectiveness for the KEPCO (Korea Electric Power Corporation) power system.

Application of resistivity monitoring with tunnel excavation area (터널 굴착에 따른 전기비저항 모니터링 기술 적용)

  • Ahn, Hee-Yoon;Jeong, Jae-Hyeung;Cho, In-Ky;Kim, Jung-Ho;Rae, Gyu-Jin
    • Journal of Korean Tunnelling and Underground Space Association
    • /
    • v.10 no.4
    • /
    • pp.405-420
    • /
    • 2008
  • Resistivity survey is one of the widely used methods for the investigation of stability of the ground or bedrock around tunnel and is also used as an essential base data for stability and reduction of construction cost through first-hand approximation of rock quality at design step. Generally, the analysis of resistivity survey data is performed by single measurement. When distribution variation of groundwater around a tunnel over time is necessary for maintenance of a tunnel, resistivity monitoring is very useful survey method to grasp distribution variation of groundwater. So we performed the grid line resistivity survey to monitoring resistivity variation for six times. And we also tried to evaluate application possibility of the resistivity monitoring for construction safety through providing detailed information on fault zones.

  • PDF

Comparison of Energy Demand in Multi-Story Buckling Restrained Braced Frame and Equivalent SDOF System (다층 비좌굴 가새골조와 등가 단자유도계의 에너지 요구량의 비교)

  • 김진구;원영섭
    • Journal of the Computational Structural Engineering Institute of Korea
    • /
    • v.16 no.2
    • /
    • pp.173-182
    • /
    • 2003
  • In equivalent static nonlinear analysis and in energy-based design, the structures are generally transformed into an equivalent SDOF system. In this study the seismic energy demands in multi story structures, such as three-, eight-, and twenty-story steel moment-resisting frames(MRF), buckling restrained braced frames(BRBF) and a damage tolerant braced frame(DTBF), are compared with those of equivalent single degree of freedom(ESDOF) systems. Sixty earthquake ground motions recorded In different soil conditions, which are soft rock, soft soil, and neat fault, were used to compute the input and hysteretic energy demands in model structures. In case the modal mass coefficient is less than 0.8, the effects of higher modes are considered in the process of converting into ESDOF According to the analysis results, the hysteretic and input energies obtained from 3 story and 8 story MRF and DTBF agreed well with the results from analysis of equivalent SDOF systems. However in the 20 story BRBF the results from ESDOF underestimated those obtained from the original structures.

A Shaking Table Test for Equipment Isolation in the NPP (II): FPS (원전기기의 면진을 위한 진동대 실험 II : FPS)

  • Kim, Min-Kyu;ZChoun, Young-Sun;Choi, In-Kil
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.8 no.5 s.39
    • /
    • pp.79-89
    • /
    • 2004
  • This paper presents the results of experimental studies on the equipment isolation effect in the nuclear containment. For this purpose, shaking table tests were performed. The purpose of this study is enhancement of seismic safety of equipment in the Nuclear Power Plant. The isolation system, known as Friction Pendulum System (FPS), combines the concepts of sliding bearings and pendulum motion was selected. Peak ground acceleration, bidirectional motion, effect of vertical motion and frequency contents of selected earthquake motions were considered. As a result, these are founded that the vertical motion of seismic wave affect to the base isolation and the isolation effect decreased in case of near fault earthquake motion.

Seismic Design of Structures in Low Seismicity Regions

  • Lee, Dong-Guen;Cho, So-Hoon;Ko, Hyun
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.11 no.4
    • /
    • pp.53-63
    • /
    • 2007
  • Seismic design codes are developed mainly based on the observation of the behavior of structures in the high seismicity regions where structures may experience significant amount of inelastic deformations and major earthquakes may result in structural damages in a vast area. Therefore, seismic loads are reduced in current design codes for building structures using response modification factors which depend on the ductility capacity and overstrength of a structural system. However, structures in low seismicity regions, subjected to a minor earthquake, will behave almost elastically because of the larger overstrength of structures in low seismicity regions such as Korea. Structures in low seismicity regions may have longer periods since they are designed to smaller seismic loads and main target of design will be minor or moderate earthquakes occurring nearby. Ground accelerations recorded at stations near the epicenter may have somewhat different response spectra from those of distant station records. Therefore, it is necessary to verify if the seismic design methods based on high seismicity would he applicable to low seismicity regions. In this study, the adequacy of design spectra, period estimation and response modification factors are discussed for the seismic design in low seismicity regions. The response modification factors are verified based on the ductility and overstrength of building structures estimated from the farce-displacement relationship. For the same response modification factor, the ductility demand in low seismicity regions may be smaller than that of high seismicity regions because the overstrength of structures may be larger in low seismicity regions. The ductility demands in example structures designed to UBC97 for high, moderate and low seismicity regions were compared. Demands of plastic rotation in connections were much lower in low seismicity regions compared to those of high seismicity regions when the structures are designed with the same response modification factor. Therefore, in low seismicity regions, it would be not required to use connection details with large ductility capacity even for structures designed with a large response modification factor.

Frture mapping and deep-seated ground water exploration in the crystalline rocks by integrated geophysical techniques (종합적 물리탐사에 의한 파쇄대 및 심부 지하수 탐사)

  • 정승환;김정호;조인기;전정수
    • The Journal of Engineering Geology
    • /
    • v.2 no.2
    • /
    • pp.113-130
    • /
    • 1992
  • Groundwater in crystalline basement is controlled primarily by tectonic fractures. It is evident that the delineation of the heavily faulted area and/or fractures deeply developped should be considerable value in deep-seated low enthalphy geothermal water. Electrical and electromagnetic methods have effectively been employed to map hydraulic faults and shear zones for groundwater exploration. In this study VLi; dipoledipole resistivity, controlled source audio~frequency magneto-telluric(CSAMT) and magnetic methods were applied in the Bomun resort area, adjacent to Kyongju city, southeastern part of Korea. The integrated geophysical tools employed in this experiment can be manifested themselves as: 1. Magnetic high for granite intrusions which is more favorable for geothermal gradient increase in depth. 2. VLF cross-over trends for mapping linear shallow conductive fractures and shear zones. 3. Dipole-dipole resistivity distributions for the deep-seated(less than 500m in depth) fractures and shear zones. The dipole-dipole resistivity field data were inverted to the true resistivity distribution with two-dimensional automatic inversion program based on the finite-difference method. 4. CSAMT provides an efficient way of delineating fractures and fault zones if the depth is greater than about 500m.

  • PDF

Operational Concept Design and Verification for Airborne SAR System (항공탑재 SAR 시스템 운용개념 설계 및 검증)

  • Lee, Hyon-Ik;Kim, Se-Young;Jeon, Byeong-Tae;Sung, Jin-Bong
    • Journal of the Korean Society for Aeronautical & Space Sciences
    • /
    • v.41 no.7
    • /
    • pp.588-595
    • /
    • 2013
  • Airborne SAR system is the imaging Radar system that is loaded on a manned or unmanned aircraft, which is in charge of high quality image acquisition and moving target detection. This paper describes the operational requirements for the Airborne SAR system and suggests the operational concept to satisfy the requirements. To be specific, it describes the interface with airborne system, state definition and transition, operation mode based on mission definition file, fault management, and data storing and transmission concept. Finally, it gives the ground test results to verify the SAR system operational concept.