• Title/Summary/Keyword: 암반특성 예측

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Application of the convergence-confinement method of tunnel design to rock masses (암반 터널에서의 시공단계를 고려한 암반-지보 거동특성 곡선적용에 관한 연구)

  • Lee, Du-Wha;Choo, Seok-Yean;Lim, Sang-Bin;Park, Young-Jin;Ahn, Sung-Joo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.4 no.2
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    • pp.143-153
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    • 2002
  • Convergence Confinement Method (CCM) makes a more simple judgement in a ground-support reaction than numerical method. Also this method is good for the applicability of construction feedback and the analysis of field measurement. However, there has been little research with respect to the application of CCM in tunnel construction. One of the problems in CCM is a decision of the time to support installation. To decide a reasonable supporting installation time, support characteristic curve and displacement characteristic curve considering construction stage are proposed. In addition, to predict displacement distribution ratio and load distribution ratio, the time dependent support reaction curve is used. Finally, through a comparison of the result between CCM and numerical analysis, the trust of this study is proved and the practical application is proposed to control resonable tunnel construction management.

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Rock Mechanics Modeling of the Site for the 2nd Step Construction of the KAERI Underground Research Tunnel (KURT) (KURT 2단계 건설부지에 대한 암석역학모델 설정)

  • Jang, Hyun-Sic;Ko, Chi-Hye;Bae, Dae-Seok;Kim, Geon-Young;Jang, Bo-An
    • The Journal of Engineering Geology
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    • v.24 no.2
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    • pp.247-260
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    • 2014
  • Rock masses at the site for the $2^{nd}$ step construction of the KAERI Underground Research Tunnel (KURT) are divided into six units to establish a rock mechanics model that is dependent on the geological characteristics and degree of joint development. The site primarily consists of three granitic units (G1, G2, and G3), two dykes (D1 and D3), and a fault zone of poor rock mass quality (F3). The F3 unit crosses the tunnel at the beginning of the site of $2^{nd}$ step construction. The rock masses of each unit are classified by RMR (Rock Mass Rating), Q-system, and RMi (Rock Mass Index), all based on borehole logging data. The deformation modulus, rock mass strength, cohesion, and friction angle for each unit are calculated using established empirical relationships. The representative rock mass classification and geotechnical parameters for the rock mass units are established, and a rock mechanics model for the site is proposed, which will be useful in the design and stability analysis of the $2^{nd}$ step construction of KURT.

A Case Study on Stochastic Fracture Network Modeling for Rock Slopes of Busan-Ulsan Highway(Reach 5) (부산-울산 고속국도(5공구)에 위치한 암반사면의 추계론적 절리연결구조 모사에 대한 사례연구)

  • Heo, In-Sill;Um, Jeong-Gi;Kim, Yang-Phil;Kim, Kook-Han;Lee, Young-Kyun
    • The Journal of Engineering Geology
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    • v.16 no.4 s.50
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    • pp.337-349
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    • 2006
  • Seven hundred and fifty one fractures of the rhyolitic tuffaceous rock masses were mapped using 6 scanlines placed on rock slope exposures that were within 8.02 km of Busan-Ulsan highway. These data were analyzed to find the number of fracture sets that exist in the rock slopes and the probability distributions of orientation, spacing, trace length and fracture size in 3-D for each of the fracture sets. All the fracture set orientation distributions exhibit high variability. The Fisher distributions were found to be unsuitable to represent the statistical distribution of orientation for most of the fracture sets. The probability distributions, gamma, exponential and lognormal were found to be highly suitable to represent the distribution of spacing and semi-trace length of fracture sets. In obtain-ing these distributions, corrections were applied for sampling biases associated with spacing and trace length. The generated fracture system in 3-D was used to make predictions of fracture traces for each fracture set on 2-D win-dows. Developed stochastic 3-D fracture network for the rock mass was validated by comparing statistical proper-ties of the observed fracture traces on scanlines with the predicted fracture traces on the scanlines. This exercise fumed out to be successful.

Coupled Thermal-Hydrological-Mechanical Behavior of Rock Mass Surrounding Cavern Thermal Energy Storage (암반공동 열에너지저장소 주변 암반의 열-수리-역학적 연계거동 분석)

  • Park, Jung-Wook;Rutqvist, Jonny;Ryu, Dongwoo;Synn, Joong-Ho;Park, Eui-Seob
    • Tunnel and Underground Space
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    • v.25 no.2
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    • pp.155-167
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    • 2015
  • The thermal-hydrological-mechanical (T-H-M) behavior of rock mass surrounding a high-temperature cavern thermal energy storage (CTES) operated for a period of 30 years has been investigated by TOUGH2-FLAC3D simulator. As a fundamental study for the development of prediction and control technologies for the environmental change and rock mass behavior associated with CTES, the key concerns were focused on the hydrological-thermal multiphase flow and the consequential mechanical behavior of the surrounding rock mass, where the insulator performance was not taken into account. In the present study, we considered a large-scale cylindrical cavern at shallow depth storing thermal energy of $350^{\circ}C$. The numerical results showed that the dominant heat transfer mechanism was the conduction in rock mass, and the mechanical behavior of rock mass was influenced by thermal factor (heat) more than hydrological factor (pressure). The effective stress redistribution, displacement and surface uplift caused by heating of rock and boiling of ground-water were discussed, and the potential of shear failure was quantitatively examined. Thermal expansion of rock mass led to the ground-surface uplift on the order of a few centimeters and the development of tensile stress above the storage cavern, increasing the potential of shear failure.

A Boundary Element Analysis for Damage and Failure Process of Brittle Rock using ERACOD (FRACOD를 이용한 취성 암석의 손상 및 파괴에 대한 경계요소 해석)

  • ;Baotang Shen;Ove Stephansson
    • Tunnel and Underground Space
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    • v.14 no.4
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    • pp.248-260
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    • 2004
  • Damage in brittle rock due to stress increase starts from initiation of microcracks, and then results in failure by forming macro failure planes due to propagation and coalescence of these discrete cracks. Conventionally, continuum approaches using macro-failure criteria or a number of elasto-plastic models have been major solution to implement rock damage and failure. However, actual brittle failure processes can be better described in phenomenological approach if initiation and propagation of discrete fractures are explicitly considered. This study presents damage and failure process of rock using a boundary element code, FRACOD, which has been developed to model fracturing process of rocks. Through a series of numerical uniaxial compressive tests, the feasibility of the developed model was verified, and realistic rock failure process was reproduced considering scale effects in rocks. In addition, the fracturing process and the corresponding rock damage in the vicinity of deep shaft in rock mass were presented as an application of this approach. This approach will be expected to contribute to finding better engineering solutions for the analysis of stability problems in brittle rock masses.

Numerical Investigation of the Radial Convergence of Circular Tunnel Excavated in Rock Mass for Generalized Hoek-Brown (일반화된 Hoek-Brown 암반에 굴착된 원형터널의 내공변위 특성 분석)

  • Lim, Kwang-Ok;Lee, Youn-Kyou
    • Tunnel and Underground Space
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    • v.28 no.1
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    • pp.59-71
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    • 2018
  • Since the generalized Hoek-Brown (GHB) function predicts the strength of the jointed rock mass in a systematic manner by use of GSI index, it is widely used in rock engineering practices. In this study, a series of 2D elasto-plastic FE analysis, which adopts the GHB criterion as a yield function, was carried out to investigate the radial convergence characteristics of circular tunnel excavated in the GHB rock mass. The effect of the plastic potential function on the elasto-plastic displacement was also examined. In the analysis, the wide range of both the $K(={\sigma}_h/{\sigma}_v)$ and GSI values are considered. For each K value, the variation of the ratio of sidewall displacement to roof displacement was calculated with varying GSI values and the obtained displacement patterns were analysed. The calculation results show that the displacement ratio significantly depends not only on the K value but also on the range of GSI value. In particular, for lower range of GSI value, the displacement ratio pattern calculated in the elasto-plastic regime is opposite to that predicted by the elasticity theory. In addition, the variation of the radial displacement ratio with GSI value for different types of plastic potential function showed similar trend.

Failure Time Prediction by Nonlinear Least Square Method with Deformation Data (계측 자료의 비선형최소자승법을 이용한 파괴시간 예측)

  • Yoon, Yong-Kyun;Kim, Byoung-Chul;Jo, Young-Do
    • Tunnel and Underground Space
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    • v.19 no.6
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    • pp.558-566
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    • 2009
  • Time-dependent behavior is a basic mechanical property of rocks. Predicting the failure time of rock structures by analyzing the time-dependent characteristic is important and problematic. It is tried to predict the failure time of tunnel, slope & laboratory creep test specimen from measured displacement(or strain) and rate with relationship suggested by Voight($\ddot{\Omega}=A\dot{\Omega}^\alpha$, where $\Omega$ is a measurable quantity such as strain & displacement and A & $\alpha$ are constants). A & $\alpha$ are estimated through applying the nonlinear least square method to the single and double integrated Voight's equations and utilized to predict the failure time. Predicted failure time is in accordance with real one except minor error. Linear inverse rate method applied to creep strain and rate yields a poor linear correlation of data and precision of predicted failure time is not better than methods using strain and rate.

An Analysis of Cut-slope Based on the Prediction of Joint Distribution inside the Cut-face (개착면 내부에서의 절리분포 예측을 통한 사면 해석)

  • Lee Chang-Sup;Chung Jin-Bo;Cho Taechin
    • Tunnel and Underground Space
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    • v.14 no.6 s.53
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    • pp.391-398
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    • 2004
  • An algebraic algorithm for predicting the joint trace distribution on the cut-face of rock slope based on the orientations and the locations of joints investigated in the borehole has been developed. Joint trace prediction is manipulated by utilizing the three dimensional plane equations of both joint planes and projection face, and the extent of trace within the projection area is calculated by considering the persistence of each joint plane. Joint trace prediction method is efficiently applied for analyzing the stability and the adequacy of support design of Gimhae Naesam cut-slope, which is structurally unstable due to slumping. Structural characteristics of rock mass is investigated by performing DOM drilling and the potential rock mass sliding inside slope face is analyzed by examining the orientations of joint planes which can induce the slope failure. Also, the efficiency of anchor support design is evaluated by considering the joint trace distribution on the anchor installation area and its sliding potential.

Verification for the Cyclic Shear Behavior of Rough Granite Joint Using Constitutive Equation (구성방정식을 이용한 거친 화강암 절리면의 주기전단거동 특성규명)

  • 김대상;박인준;이희석
    • Journal of the Korean Geotechnical Society
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    • v.18 no.1
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    • pp.141-152
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    • 2002
  • Although a number of constitutive models have been proposed to define the behavior of geotechnical materials including elastic, plastic, and dynamic response, flew numerical models have been developed for the cyclic shear behavior of rock joints or interfaces. Such realistic constitutive models play an important role in analyzing and predicting the response of joints under dynamic loads. The purpose of this research is to verify the constitutive model modified for rough granite joints based on Disturbed State Concept(DSC) model, which has been successfully verified with respect to other materials such as dry sand-steel interface and wet sand-concrete interface. Furthermore, DSC model is compared and verified with respect to cyclic shear tests and numerical analysis results based on Plesha model. Based on the results of this research, it can be stated that DSC model is capable of characterizing the cyclic shear behavior of rough granite joints under dynamic loads.

Analysis on the TBM Penetration Rates in Extremely Hard Rocks (극경암에서의 전단면터널 굴착속도 분석연구)

  • Park, Chul-Whan;Synn, Joong-Ho;park, Chan;Kim, Min-Kyu;Chung, So-Keul;Kim, Hwa-Soo
    • Tunnel and Underground Space
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    • v.10 no.4
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    • pp.526-532
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    • 2000
  • The uniaxial compressive strength of rock mass is known as the major factor in the assessment of drillability and the optimum excavation design in full-face tunnel excavation by TBM. Referring to worldwide cases, TBM has been applied mostly to the rock mass within the strength range of 80~250 MPa. Recently, a water way tunnel has been constructed as a part of Milyang dam project by TBM within the rock masses where the rock type is mainly granite with some granophyre, hornfels and andesite. Their uniaxial compressive strengths in extended area are estimated higher than 260 MPa. In this paper, the relation between the penetration rate and the rock mass properties is analyzed and TBM application to the very hard rocks is discussed. As a result that three suggestions to predict the TBM net penetration rate are analyzed, NTH method seems a better approach than other methods in the extremely hard rocks. NTH prediction matches with the results of actual values with the variations of 2~20%. Hardness measurement by Schmidt hammer and RMR estimation are carried out along the L = 5.3 km entire TBM tunnel alignment. The net penetration rate measured monthly is shown to be reciprocally proportional to Schmidt rebound hardness and RMR where coefficients of correlation, $R^2$are 0.705 and 0.777 respectively. As a result, they are good quantitative indices for the prediction of TBM net penetration rate in the extremely hard rocks. Magnitude of in-situ stress has a certain effect on TBM performance, and it is required to measure the in-situ stresses in TBM excavation design.

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