• Title/Summary/Keyword: Ground loss

Search Result 861, Processing Time 0.028 seconds

Influence Ground Sinking with Variation of Ground Water Level (지하수위 변화에 따른 지반함몰 영향연구)

  • Kim, Suk-Ja;Jung, Kwan-Sue
    • Journal of the Society of Disaster Information
    • /
    • v.14 no.4
    • /
    • pp.399-408
    • /
    • 2018
  • Purpose: Recently, the ground subsidence has caused social problem, because it occurred life and economic damage. Method: Ground subsidence is different from a sink hole. Ground subsidence occurred cavities from loss of by groundwater flow, surface layer is collapsed due to relaxation and expansion. Results: According to the survey, the caused of ground subsidence are classified as ground cavities, surrounding ground relaxation and pipe joint failure. Conclution: Cavities of ground is mainly caused by cavities formed by rainfall induced infiltration of the heavy rainfall, loss of soil due to rise and fall of ground water level and repeated sewage runoff.

Low-Loss Broadband Planar Balun with CPW-to-Slotline Transition for UHF Applications

  • Hong, Young-Pyo;Yook, Jong-Gwan
    • Journal of electromagnetic engineering and science
    • /
    • v.9 no.3
    • /
    • pp.146-151
    • /
    • 2009
  • This paper presents a low-loss broadband balun that uses a coplanar waveguide-to-slotline field transformation. It operates over a very wide frequency range and is of compact size since it does not depend on a resonant structure. To analyse imbalance, the coplanar wavelength(CPW) input ground is connected to the CPW output ground through various capacitors to introduce common-mode impedances. As the common-mode impedance increased the imbalance became significantly higher at the higher-frequency band compared with the lower-frequency band. The bias-circuit approach is used to improve the operation bandwidth of the lower-frequency band. The measured results show a passband of 200 MHz to 2 GHz, an insertion loss of less than 0.75 dB, and a size of $20{\times}14\;mm$. The amplitude imbalance is approximately 0.3 dB and the phase imbalance is less than $6^{\circ}$ over the entire operational range.

Applications of Seismic Disaster Simulation Technology on Risk Management

  • Yeh, Chin-Hsun
    • 한국방재학회:학술대회논문집
    • /
    • 2010.02a
    • /
    • pp.16-24
    • /
    • 2010
  • This paper introduces the applications of Taiwan Earthquake Loss Estimation System (TELES), which is developed by the National Center for Research on Earthquake Engineering (NCREE). Seismic disaster simulation technology (SDST) integrates geographical information system to assess the distribution of ground shaking intensity, ground failure probability, building damages, casualties, post-quake fires, debris, lifeline interruptions, economic losses, etc. given any set of seismic source parameters. The SDST may integrate with Taiwan Rapid Earthquake Information Release System (TREIRS) developed by Central Weather Bureau (CWB) to obtain valuable information soon after large earthquakes and to assist in decision-making processes to dispatch rescue and medical resources more efficiently. The SDST may also integrate with probabilistic seismic source model to evaluate various kinds of risk estimates, such as average annual loss, probable maximum loss in one event, and exceeding probability curves of various kinds of losses, to help proposing feasible countermeasures and risk management strategies.

  • PDF

Rebar corrosion effects on structural behavior of buildings

  • Yuksel, Isa
    • Structural Engineering and Mechanics
    • /
    • v.54 no.6
    • /
    • pp.1111-1133
    • /
    • 2015
  • Rebar corrosion in concrete is one of the main causes of reduction of service life of reinforced concrete buildings. This paper presents the influence of rebar corrosion on the structural behavior of reinforced concrete (RC) buildings subjected to strong earthquake ground motion. Different levels of rebar corrosion scenarios were applied on a typical four story RC frame. The deteriorated conditions as a result of these scenarios include loss in cross-sectional area and loss of mechanical properties of the reinforcement bars, loss in bond strength, and loss in concrete strength and its modulus of elasticity. Dynamic analyses of the frame with different corrosion scenarios are performed with selected strong earthquake ground motion records. The influences of degradation in both concrete and reinforcement on structural behavior are investigated by comparing the various parameters of the frame under different corrosion scenarios with respect to each other. The results show that the progressive deterioration of the frame due to rebar corrosion causes serious structural behavior changes such as change in failure mode. The intensity, propagation time, and extensity of rebar corrosion have very important effects on the level of degradation of steel and concrete, as well as on the earthquake behavior of the structure.

Earthquake Loss Estimation of the Gyeongju Area using the Deterministic Method in HAZUS (HAZUS의 결정론적 방법을 이용한 경주지역의 지진재해예측)

  • Kang, Su-Young;Kim, Kwang-Hee;Suk, Bong-Chool;Yoo, Hai-Soo
    • 한국방재학회:학술대회논문집
    • /
    • 2008.02a
    • /
    • pp.597-600
    • /
    • 2008
  • Observed ground motions from the January 2007 magnitude 4.9 Odaesan earthquake and the events occurring in the Gyeongsang provinces are compared with the previously proposed ground attenuation relationships in the Korean Peninsula to select most appropriate one. The selected relationship from the ones for the Korean Peninsula has been compared with attenuation relationships available in HAZUS. Then, the attenuation relation for the Western United States proposed by Sadigh et al.(1997) for the Site Class B has been selected for this study. It has been used for the earthquake loss estimation of the Gyeongju area located in southeast Korea using the deterministic method in HAZUS with a scenario earthquake (M=6.7). Application of the improved methodology for loss estimation in Korea will help decision makers for planning disaster responses and hazard mitigation.

  • PDF

A Study on the Behavior of Surface Settlement due to the Excavation of Twin TBM Tunnels in the Clay Grounds (점토지반에서 TBM 병렬터널 굴진 시 지표침하거동에 대한 연구)

  • You, Kwangho;Jung, Suntae
    • Journal of the Korean GEO-environmental Society
    • /
    • v.20 no.2
    • /
    • pp.29-40
    • /
    • 2019
  • Mechanized constructions have been frequently increased in soft ground below sea bed or river bed, for urban tunnel construction, and for underpinning the lower part of major structures in order to construct a safer tunnel considering various risk factors during the tunnel construction. However, it is difficult to estimate the subsidence behavior of the ground surface due to excavation and needs to be easily predicted. Thus, in this study, when a twin tunnel is constructed in the soft ground, it is proposed a simpler equation relating to the settlement behavior and a corrected formula applicable to soft ground and large diameter shield tunnels based on the previously proposed theory by Peck (1969). For this purpose, it was analyzed to long-term measurement values such as the amount of maximum settlement, the subsidence range by ground conditions, and interference volume loss due to the parallel construction, etc. As a result, a equation was suggested to predict the amount of maximum settlement in the soft sediment clay ground where is located at the upper part of the excavation site. It is turned out that the proposed equation is more suitable for measurement data in Korea than Peck (1969)'s.

Validation of Load Calculation Method for Greenhouse Heating Design and Analysis of the Influence of Infiltration Loss and Ground Heat Exchange (온실 난방부하 산정방법의 검증 및 틈새환기와 지중전열의 영향 분석)

  • Shin, Hyun-Ho;Nam, Sang-Woon
    • Horticultural Science & Technology
    • /
    • v.33 no.5
    • /
    • pp.647-657
    • /
    • 2015
  • To investigate a method for calculation of the heating load for environmental designs of horticultural facilities, measurements of total heating load, infiltration rate, and floor heat flux in a large-scale plastic greenhouse were analyzed comparatively with the calculation results. Effects of ground heat exchange and infiltration loss on the greenhouse heating load were examined. The ranges of the indoor and outdoor temperatures were $13.3{\pm}1.2^{\circ}C$ and $-9.4{\sim}+7.2^{\circ}C$ respectively during the experimental period. It was confirmed that the outdoor temperatures were valid in the range of the design temperatures for the greenhouse heating design in Korea. Average infiltration rate of the experimental greenhouse measured by a gas tracer method was $0.245h^{-1}$. Applying a constant ventilation heat transfer coefficient to the covering area of the greenhouse was found to have a methodological problem in the case of various sizes of greenhouses. Thus, it was considered that the method of using the volume and the infiltration rate of greenhouses was reasonable for the infiltration loss. Floor heat flux measured in the center of the greenhouse tended to increase toward negative slightly according to the differences between indoor and outdoor temperature. By contrast, floor heat flux measured at the side of the greenhouse tended to increase greatly into plus according to the temperature differences. Based on the measured results, a new calculation method for ground heat exchange was developed by adopting the concept of heat loss through the perimeter of greenhouses. The developed method coincided closely with the experimental result. Average transmission heat loss was shown to be directly proportional to the differences between indoor and outdoor temperature, but the average overall heat transfer coefficient tended to decrease. Thus, in calculating the transmission heat loss, the overall heat transfer coefficient must be selected based on design conditions. The overall heat transfer coefficient of the experimental greenhouse averaged $2.73W{\cdot}m^{-2}{\cdot}C^{-1}$, which represents a 60% heat savings rate compared with plastic greenhouses with a single covering. The total heating load included, transmission heat loss of 84.7~95.4%, infiltration loss of 4.4~9.5%, and ground heat exchange of -0.2~+6.3%. The transmission heat loss accounted for larger proportions in groups with low differences between indoor and outdoor temperature, whereas infiltration heat loss played the larger role in groups with high temperature differences. Ground heat exchange could either heighten or lessen the heating load, depending on the difference between indoor and outdoor temperature. Therefore, the selection of a reference temperature difference is important. Since infiltration loss takes on greater importance than ground heat exchange, measures for lessening the infiltration loss are required to conserve energy.

Analysis of Response Change of Structure due to Tunnel Excavation Conditions in Sand Ground (모래지반에서 터널 굴착조건들을 반영한 상부 블록구조물의 거동변화 분석)

  • Son, Moorak
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.33 no.4
    • /
    • pp.1541-1549
    • /
    • 2013
  • This study investigates the response of structures to tunnelling-induced ground movements in sand ground, varying tunnel excavation condition (tunnel depth and diameter), tunnel construction condition (ground loss), ground condition (loose sand and dense sand). Four-story block-bearing structures have been used because the structueres can easily be characterized of the extent of dmages with crack size and distribution. Numerical parametric studies have been used to investigae of the response of structures to varying tunnelling conditions. Numerical analysis has been conducted using Discrete Element Method (DEM) to have real cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The results of structure responses from various parametric studies have been integrated to consider tunnel excavation condition, tunnel construction condition, and ground condition and provided as a relationship chart. Using the chart, the response of structures to tunnelling can easily be evaluated in practice in sand ground.

Numerical investigation on the effect of backfill grouting on ground behavior during shield TBM tunneling in sandy ground (사질토 지반을 통과하는 쉴드 TBM에서 뒤채움 그라우팅이 지반 거동에 미치는 영향에 대한 수치해석적 연구)

  • Oh, Ju-Young;Park, Hyunku;Chang, Seokbue;Choi, Hangseok
    • Journal of Korean Tunnelling and Underground Space Association
    • /
    • v.20 no.2
    • /
    • pp.375-392
    • /
    • 2018
  • The shield TBM method is widely adopted for tunneling works in urban area because it has more beneficial ways to control settlement at ground surface than conventional mined tunneling. In the shield tunneling, backfill grouting at tail void is crucial because it is supposed not only to restraint ground deformation around tail void during excavation but also to compensate precedent ground settlement by pushing up the ground with highly pressurized grout. However, the tail void grouting has been found to be ineffective for settlement compensation particularly in sandy ground, which might be caused by complicate interaction between ground and tail void grouting. In this paper, the effects of tail void grouting on behavior of ground in shield TBM tunneling were investigated based on 3-dimensional finite element analyses. The results of numerical analyses indicated that backfill grouting actually reduces settlement by degrading settlement increasing rate in excavation, which means decrease of volume loss. Meanwhile, the grouting could not contribute to compensate the precedent settlement, because reduction of volume loss by grouting was found to be counterbalanced by volume change of ground.

Modification of the Existing Binders for Highly-Shattering, Short-Stem Rice Varieties (II) (탈립성(脱粒性), 단간종(短稈種)인 통일계품종(統一系品種)에 적합(適合)한 바인더의 개량(改良) 개발(開発)에 관(関)한 연구(硏究) (II))

  • Chung, C.J.;Choi, H.S.;Ryu, K.H.;Koh, H.K.;Kim, S.R.
    • Journal of Biosystems Engineering
    • /
    • v.8 no.2
    • /
    • pp.18-25
    • /
    • 1983
  • The binders introduced in Korea were originally designed to be used for Japonica varieties which have realtively long stem and are highly resistant to shattering. In order to use it for Tongil varieties which are short and easy to be shattered, mechanical modifications are necessary to reduce a grain loss incurred during its operation. This study was intended to investigate the binding unit, one of the major factors affecting grain losses. The binding parts of three binders used in Korea were analyzed and the grain loss was experimentally assessed for these binders. The results obtained from this study are summarized as follows: 1. From the motion analysis of discharge mechanism, the trajectory of the discharge arm appeared to be either circular or skewed elliptic. The velocity of a circular path mechanism was constant and smaller than that of a skewed elliptic path mechanism. The discharge grain loss of the former was about twice less than that of the latter. 2. It was found that the grain loss incurred due to the collision of the paddy bundles and ground was considerably high for Tongil varieties. The auxiliary discharge bar gave a significant influence on the motion and posture of the bundles, and the degree of impact on ground. 3. The installation of an auxiliary bar, which guides the paddy bundles smoothly to ground in order to reduce impact when the bundles fall down on ground, appeared to be very effective since the grain losses could be decreased by about 1.6 percentage point. However, the guide bar should be installed after some mechanical modification to reduce the velocity of discharge arm has been made.

  • PDF