• Title/Summary/Keyword: Poor ground

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A study on the characteristics of shallow overburden railway tunnel behavior under the existing road (기존도로하부 저토피 통과구간 철도터널 거동특성에 관한 연구)

  • Seo, Yoon-sic;Kim, Yeon-deok;Moon, Gyeong-seon;Kim, Hyeob;Kim, Sang-Hwan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.6
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    • pp.1045-1058
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    • 2017
  • This paper is a study on railway tunnel behavior characteristic of shallow overburden under the existing road. In order to understand the behavior characteristics of the ground deformation during tunnel excavation, a horizontal rod extensometers were installed in the passage area of the shallow overburden tunnel under the road, and the measurement and analysis were carried out. To compare the in situ measurement, three dimensional numerical analysis with ground condition and construction step was carried out using MIDAS NX. As a result of the field measurement, large preceding settlement occurred where the poor ground condition with shallow overburden excavation has been conducted. As a result of the numerical analysis, the largest settlement occurred at the shallow overburden point where the ground condition was poor. Therefore, in the shallow overburden section where the soil condition is poor and a sufficient depth can't be secured and the arching effect of the ground around the tunnel can't be expected, careful attention should be paid to the application of stiffness reinforcement measures and to minimize ground loosening.

Characterization of face stability of shield tunnel excavated in sand-clay mixed ground through transparent soil models

  • YuanHai Li;XiaoJie Tang;Shuo Yang;YanFeng Ding
    • Geomechanics and Engineering
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    • v.33 no.5
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    • pp.439-451
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    • 2023
  • The construction of shield tunnelling in urban sites is facing serious risks from complex and changeable underground conditions. Construction problems in the sand-clay mixed ground have been more reported in recent decades for its poor control of soil loss in tunnel face, ground settlement and supporting pressure. Since the limitations of observation methods, the conventional physical modelling experiments normally simplify the tunnelling to a plane strain situation whose results are not reliable in mixed ground cases which exhibit more complicated responses. We propose a new method for the study of the mixed ground tunnel through which mixed lays are simulated with transparent soil surrogates exhibiting different mechanical properties. An experimental framework for the transparent soil modelling of the mixed ground tunnel was established incorporated with the self-developed digital image correlation system (PhotoInfor). To understand better the response of face stability, ground deformation, settlement and supporting phenomenon to tunnelling excavation in the sand-clay mixed ground, a series of case studies were carried out comparing the results from cases subjected to different buried depths and mixed phenomenon. The results indicate that the deformation mode, settlement and supporting phenomenon vary with the mixed phenomenon and buried depth. Moreover, a stratigraphic effect exists that the ground movement around mixed face reveals a notable difference.

A Case Study on Elephant Foot Method for Tunnelling in the Soft Ground (토사터널에서의 각부보강공법 적용성 연구)

  • Park, Chi-Myeon;Lee, Ho;Park, Jae-Hoon;Yoon, Chang-Ki;Hwang, Je-Don
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.863-874
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    • 2009
  • The engineering characteristics and the reinforcement effect of the elephant foot method were discussed with parametric study. The elephant foot method is adopted to support the loads transferred from tunnel crown and improve bearing capacity of elephant foot in poor ground condition. The evaluation of reinforcement effect, which has the mechanical relationship between ground condition, footing size and reinforcement system, was carried out through the previous research and numerical analysis. In addition, the simple design chart was proposed to estimate the applicability of the elephant foot reinforcement method. It will be practical for the engineer to determine the optimum reinforcement method for safe tunnelling in soft ground condition.

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Ayurveda publishing: The ground realities, concurrent problems and possible remedies

  • Rastogi, Sanjeev;Singh, Harsh Ram
    • CELLMED
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    • v.7 no.4
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    • pp.17.1-17.3
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    • 2017
  • Ayurveda is gradually getting more acceptances in the world. The fact is visible through increasing number of Ayurveda articles in leading medical journals and also through the chapters on Ayurveda in various biomedical publications. Although the world is now looking up at the authentic information about Ayurveda, the status of Ayurveda publishing in India is not very promising. Poor workmanship while preparing the articles on Ayurveda and non professional approaches in publishing are the reasons of the poor show and this requires to be seriously taken up.

An Experimental Study on Freezing-Thawing Resistance of Concrete Using Ground Granulated Blast-Furnace Slag (고로슬래그 미분말을 사용한 콘크리트의 동결융해 저항성에 대한 실험적 연구)

  • 남용혁;최세규;김동신;김생빈
    • Proceedings of the Korea Concrete Institute Conference
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    • 1996.10a
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    • pp.148-153
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    • 1996
  • Concrete with ground granulated blast-furnace slag can be affected by frost attack because the reaction of hydration is slow at the early age. In this study, therefore, the freezing and thawing test has been carried out to investigate the freezing and thawing resistance on concrete with ground granulated blast-furnace slag. The freezing and thawing test has been performed on concrete a blended cement, which was substituted by ground granulated blast-furnace slag with 4 kinds of ratio (non-admixture, 20%, 40% and 60%). And also tested on concrete added the AE agents to the concrete of same mix proportion to search the improvement effects about the resistance. As a result, the freezing and thawing resistance showed a tendency of reduction in proportion to the increase of the substitution ratio. For non-AE concrete, resistances of the freezing and thawing were very poor as the durability index indicated less than 5.8%. For AE concrte, resistance of the freezing and thawing were excellent as the durability index indicated more than 80.9%.

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Influences of Power Fluctuation on In-Situ Ground Thermal Response Testing (지중 열반응 현장시험에서 소비전력 변동의 영향)

  • Kim, Jin-Sang;Park, Keun-Woo
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.707-712
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    • 2006
  • Knowing the ground thermal conductivity is very importnat in designing ground heat exchangers. Knowledge of the ground soil and rock composition information dose not guarantee the prediction of accurate thermal information. In Situ testing of ground heat exchangers is becoming popular. However, in situ testing are performed at construction sites in real life. Adequate data collection and analysis are not easy mainly due to poor power quality. Power fluctuation also causes the fluctuation of received data. The power quality must be maintained during the entire in situ testing processes. To accurately analyse the test data, the understanding of the response of the power fluctuation is essential. Testing under the power quality varied by tester is very difficult. Analyzing power variation by numerical simulation is a realistic option. By varying power in a sinosuidal manner, its effects on predicting thermal conductivity from thermal response plots made from the test data are examined.

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Development study of ground water management system making use of GIS ( Well analysis program, connection program of ground water modeling ) (GIS를 이용한 지하수관리시스템 개발 연구 (관정분석 프로그램, 지하수모델링 연계프로그램))

  • 이병호;김양빈;설민구;송양권;송무영
    • Proceedings of the KSEG Conference
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    • 2002.04a
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    • pp.235-248
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    • 2002
  • Ground water development skill growth and life circumstances improvement increase ground water use. So managerial difficulties and various problems about ground water occur. Poor ground water management organization, lack of management person, thoughtless development add ground water pollution and lack of water volume. And local excessive developments or abandoned well occur. This paper presents ground water management system model making use of GIS and helps effective management by realizing necessary analysis functions in ground water management system and ground management methods. Local information of ground water recorded and development data, site examination data made D/B. And linearment analysis data making use of a satellite image data, hydraulic test data, the quality of water examination data, these local characteristic values made out thematic maps and making use of these data can form elementary data of ground water modeling It makes easy to understand environmental development conditions and pollution source conditions about new ground water development location, linearment growth, DRASTIC, the quality of water examination. Ground water management system making use of these functions can choose right location of ground water.

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A Study on Some Factors Affecting the Poor Harvest of Laver in Kwangyang Bay, 1986 (1986년 하동 김 양식장의 작황감소 원인에 관한 연구)

  • SONG Choon Bok;HONG Jae-Sang;KANG Jae Won
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.20 no.4
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    • pp.328-340
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    • 1987
  • In order to clarify major reasons of a poor harvest, the Porphyra-cultivation ground was investigated in Kwangyang Bay in terms of the laver production per unit area, diseases, and fouling organisms from January to April in 1986. The laver production per unit area of the control station was more than that of the study area at 'Soppal' cultivation ground, while the difference at the cultivation groud using 'nets' seemed to be insignificant. The vertical attachment range of laver was directly associated with the production per unit area at 'Soppal' cultivation ground. The number of young thalli of 1-3 mm length was almost similar between control and study sites at 'nets' cultivation ground. Two kinds of diseases in cultured laver, the crape and shot hole, were prevalent during the study period. However, the affected thalli were gradually decreased at the end of the study period. Major fouling organisms attached to 'Soppal' were Balanus albicostatus, Enteromorpha prolifera, Capsosiphon fulvescens, and Scytosiphon lomentaria. In conclusion, the poor harvest of laver in 1986 may result from such following problems as the decrease in vertical attachment range of laver and fouling problems as the decrease in vertical attachment range of laver and fouling organisms at 'Soppal' cultivation ground, prevalence of certain diseases, changes in environmental conditions, arrangement and maintenance of facilities for laver cultivation.

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The effects of the face reinforcement at shallow tunnels in fractured rock masses (파쇄대 암반에서 얕은 심도의 터널 굴착시 막장보강효과에 관한 연구)

  • Nam, Kee-Chun;Heo, Young;You, Kwang-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.5 no.4
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    • pp.323-336
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    • 2003
  • Recently, the development of tunnel reinforcement method has been required relating to the shallow tunnelling in soft ground. In this study, the improvement method on tunnel stability is proposed by evaluating the efficiency of face reinforcement which enables to control extrusion of advance core, however, it is often neglected in urban tunnelling under the poor ground conditions. Systematic pre-confinement ahead of the face improves the tunnel stability, subsequently, displacement of the crown and surface settlement can be restrained by proper method. 3-dimensional numerical analysis including horizontal reinforcement modelling on a face is applied to estimate the behaviour of a tunnel in relation to the ground and reinforcement conditions. Consequently, extrusion at the face decreases significantly after using the horizontal reinforcement and the effect of reinforcement is much increased in case of applying the supplemental reinforcement ahead of the face together. Especially, confinement effect around the tunnel and the core is proved by means of the core reinforcement in poor ground conditions.

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Evaluation of Ground-Water Sampling Techniques for Analysis of Chlorofluorocarbons (지하수의 CFCs(Chlorofluorocarbons) 조사를 위한 시료 채취 방법의 평가)

  • 고동찬;이대하
    • Journal of Soil and Groundwater Environment
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    • v.8 no.2
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    • pp.1-8
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    • 2003
  • Two types of ground-water sampling techniques for CFCs (chlorofluorocarbons) analysis, the cold-welded copper tube method and flame-sealed borosilicate glass ampule method, were compared and evaluated. CFCs concentrations by the copper tube method showed a poor reproducibility among triplicates whereas those by the glass ampule method showed a good agreement and relative standard deviations of triplicates were less than 5%. The poor reproducibility of the copper tube method appears to be attributed to the incomplete sealing in connection between faucets of wellhead and the sampling apparatus. The copper tube method also showed higher CFCs concentrations than the glass ampule method, which is more pronounced for CFC-11 than for CFC-12. The plastic tubings and rubber gasket of faucets in case of the copper tube method possibly contaminated the samples with CFC-11 and CFC-12. The potential of CFCs contamination for the glass ampule method was eliminated by using stainless steel and Nylon only and by connecting the sampling equipment directly to the main discharge pipe of wellhead. The validity of the glass ampule method were also verified by detecting very low level of CFCs for the ground-water sample which is old enough to have negligible CFCs.