• Title, Summary, Keyword: 암반등급

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A numerical study of the influence of rock mass classes boundary on tunnel stability (암반 등급 경계가 터널 안정성에 미치는 영향에 관한 수치해석적 연구)

  • Kim, Gyeomyeon;Jung, Chanmook;Lee, Yongjun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.6
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    • pp.825-835
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    • 2019
  • When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.

Estimation of Tunnel Convergence Using Statistical Analysis (통계처리를 활용한 터널 내공변위의 분석에 관한 연구)

  • 김종우
    • Tunnel and Underground Space
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    • v.13 no.2
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    • pp.108-116
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    • 2003
  • Measured convergence data of a tunnel were investigated by means of statistical and regression analysis, where the rock mass were mainly composed of andesite and granite. The rock mass around tunnel were classified by RMR method into five different ratings, and then convergence data which belong to individual ratings were statistically processed to find out the appropriate regression equations. Exponential equations were better coincided with measured data than logarithmic equations. As the number of rock mass rating was increased, the magnitude and standard deviation of convergence were increased. Final convergence data were also investigated to study the relevance with both maximum displacement rate and early measured convergence. Some brief results of their relevance are presented. For instance, the regression coefficient between final convergence and maximum displacement rate was turned out to be 0.87 for this studied tunnel.

An estimation technique of rock mass classes in undrilled region (미시추구간의 암반등급 산정 기법에 관한 연구)

  • 유광호
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.141-152
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    • 2003
  • 터널 설계를 위한 조사 있어서, 요사이 시추공 조사는 물론 탄성파 탐사, 전기 비저항 탐사 등의 물리탐사가 빈번히 행해지고 있는 실정이다. 따라서 최적의 지반평가(암반 등급 등)를 위해 조사에서 얻어지는 모든 자료를 체계적으로 최대한 활용할 수 있는 방법이 절실히 요구되고 있다. 많은 연구자들이 정량적 데이터가 부족한 경우에 대처하기 위해 정상적 데이터의 이용을 적극 제안해 왔다. 본 연구에서는 신뢰도가 다른 두 종류의 자료, 즉 시추공자료와 물리탐사 자료를 활용하여 시추가 되지 않은 구간의 암반등급을 추정하는 방법을 지구통계학적 이론에 근거하여 소개하고자 한다.

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Estimation of Rock Mass rating(RMR) and Assessment of its Uncertainty using Conditional Simulations (조건부 모사 기법을 이용한 암반등급의 예측 및 불확실성 평가에 관한 연구)

  • Hong Chang-Woo;Jeon Seok-Won;Koo Chung-Mo
    • Tunnel and Underground Space
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    • v.16 no.2
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    • pp.135-145
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    • 2006
  • In this study, conditional simulation was conducted to estimate rock mass rating(RMR) in unsurveyed regions. Sequential Gaussian simulation(SGS) and sequential indicator simulation(SIS) were applied for estimating RMR from the bore hole logging data. The uncertainty of SGS and SIS was verified by sample cross validation. A subset composed of 5 bore hole logging data among the original 30 bore hole logging data was set aside as test data. The remainder was training data. The quality of SGS and SIS estimation on the testing data reflects how well it would perform in an unsupervised setting. SGS and SIS were useful stochastic methods to estimate the spatial distribution of rock mass classes correctly and assess the uncertainty of estimation quantitatively. The result of conditional simulation can offer useful information of rock mass classes such as RMR in unsurveyed regions.

RMR Evaluation by Integration of Geophysical and Borehole Data using Non-linear Indicator Transform and 3D Kriging (암반등급 해석을 위한 비선형 지시자 변환과 3차원 크리깅 기술의 물리탐사 및 시추자료에 대한 적용)

  • Oh, Seo-Khoon
    • Journal of the Korean earth science society
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    • v.26 no.5
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    • pp.429-435
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    • 2005
  • 3D RMR (Rock Mass Rating) analysis has been performed by applying the Geostatistical integration technique for geophysical and borehole data. Of the various geostatistical techniques for the integrated data analysis, in this study, we applied the SKlvm (Simple Kriging with local varying means) method that substitutes the values of the interpreted geophysical result with the mean values of the RMR at the location to be inferred. The substitution is performed by the indicator transform between the result of geophysical interpretation and the observed RMR values at borehole sites. The used geophysical data are the electrical resistivity and MT result, and 10 borehole sites are investigated to obtain the RMR values. This integrated analysis makes the interpretation to be more practical for identifying the realistic RMR distribution that supports the regional geological situation.

A study on correlation between electrical resistivity obtained from electrical resistivity logging and rock mass rating in-situ tunnelling site (전기비저항 검층으로 얻은 전기비저항과 터널 현장 암반등급의 상관관계에 관한 연구)

  • Lee, Kang-Hyun;Seo, Hyung-Joon;Park, Jin-Ho;Ahn, Hee-Yoon;Kim, Ki-Seog;Lee, In-Mo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.14 no.5
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    • pp.503-516
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    • 2012
  • Rock mass rating (RMR) is the key factor when designing the appropriate support pattern of tunnel projects. Borehole drilling is usually performed along the tunnel route in order to determine the rock mass rating to be used for tunnel design. The rock mass rating at the non-boring region between boreholes is usually assessed through geophysical surveys such as electrical prospecting, seismic prospecting, etc. Many studies were carried out to find out the correlation between electrical resistivity and rock mass rating. However, most researches were aimed at obtaining the relationship between the two parameters utilizing experimental results obtained from laboratory tests or electrical prospectings. In this paper, efforts were made to analyze and obtain relationships between the electrical resistivity obtained from in-situ electrical resistivity logging data and the rock mass rating. Correlation studies using field data showed that the electrical resistivity is highly correlated with the rock mass rating with the determination coefficient more than 90%. The correlation analysis was also carried out between RMR classification parameters and the electrical resistivity. It was shown that the correlation between the condition of discontinuities and the electrical resistivity was very high with the determination coefficient more than 80%; that between the groundwater condition and the electrical resistivity was very low with the determination coefficient less than 57%.

An Estimation Technique of Rock Mass Classes for a Tunnel Design (터널 설계를 위한 암반등급 산정 기법에 관한 연구)

  • 유광호
    • Journal of the Korean Geotechnical Society
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    • v.19 no.5
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    • pp.319-326
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    • 2003
  • In site investigation for tunnel designs, nowadays, geophysical exploration such as seismic exploration and electric resistivity exploration as well as drilling logging is frequently carried out. A method which can systematically make the utmost use of all available data obtained from investigation, therefore, is strongly required for the optimal evaluation of ground conditions in terms of rock mass class, etc. Many researchers have proposed using qualitative data to cope with the lack of quantitative data. In this study, an evaluation technique of rock mass classes in undrilled region was proposed based upon multiple indicator kriging method which is a geostatistical technique. It was shown that two types of data with different degree of uncertainty, for example, drilling logging data and geophysical exploration data, could be simultaneously utilized in evaluating rock mass classes for a real tunnel design.

Geostatistical Integration of Seismic Velocity and Resistivity Data for Probabilistic Evaluation of Rock Quality (탄성파 속도와 전기비저항 자료의 지구통계학적 복합해석에 의한 암반등급의 확률적 평가)

  • Oh, Seok-Hoon;Suh, Baek-Soo
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.293-298
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    • 2007
  • A new way to integrate various geophysical information for evaluation of RQD was developed. In this study, we does not directly define the RQD value where borehole data are not sampled. Instead, we infer the probability of RQD values with prior probability of data directly obtained from borehole, and secondary supporting probability from resistivity and seismic tomography data. First, we applied the geostatstical indicator kriging to get prior probability of RQD value, and indicator kriging with soft data to get the supporting probability from resistivity and seismic data. And we finally applied the permanence ratio rule to integrate these information. The finally obtained result was also analyzed to fully utilize the probabilistic features. For example, we showed the probability of wrongly classifying the RQD evaluation and vice versa. This kind of analytical result may be used for decision making process based on the geophysical exploration.

Geostatistical inversion of geophysical data for estimation of rock quality (물리탐사 자료의 지구통계학적 역산에 의한 암반강도 추정)

  • Oh, Seok-Hoon;Suh, Baek-Soo
    • 한국지구물리탐사학회:학술대회논문집
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    • pp.63-67
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    • 2008
  • Geostatistical inverse approach using geophysical data was applied to indirectly make the RMR classification at points apart from boreholes. The geostatistical appoach was usually used to find optimized estimation which supports two or more different physical properties at unsampled points. However, in this study, an approach to solve inverse problem was proposed. The primary variable, RMR values obtained at known boreholes, is geostatistically simulated with many realization at pre-defined grid point according to the variogram model. The simulated values are sequentially compared with the physical property resulted from geophysical survey at an arbitrary grid point, and the most similar one is chosen. This process means that the spatial distribution of primary variable, RMR, is conformed well to the original pattern of the borehole observation, and ensure to fit the geophysical survey result to reflect the correlation between different physical properties.

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A study on the estimation of rock mass classes using the information off a tunnel center line (터널 중심선으로부터 이격된 자료를 활용한 미시추구간의 암반등급 산정에 관한 연구)

  • You, Kwang-Ho;Lee, Sang-Ho;Choo, Suk-Yeon;Jue, Kwang-Sue
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.2
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    • pp.101-111
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    • 2004
  • In order to guarantee the stability of a tunnel and its optimum design, it is very important to obtain enough ground investigation data. In realty, however, it is not the case due to the limitation of measuring spatially distributed data and economical reasons. Especially, there are regions where drilling is impossible due to civil appeal and mountainous topology, and it is also difficult to estimate rock mass classes quantitatively with only geophysical exploration data. In this study, therefore, 3 dimensional multiple indicator kriging (3D-MI kriging), which can incorporate geophysical exploration data and drill core data off a tunnel center line, is proposed to cope with such problems. To this end, two dimensional mutiple indicator kriging, which is one of the geostatistical techniques, is extended for three dimensional analysis. Also, the proposed 3D-MI kriging was applied to determine the rock mass classes by RMR system for the design of a Kyungbu express rail way tunnel.

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