• 화약ㆍ발파
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• 제27권1호
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• pp.21-31
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• 2009

터널의 굴착이나 응력 재분포에 의해 터널 주변에는 암반 손상대(EDZ) 구간이 발생하게 되며, 이는 암반의 역학적 수리적 물성변화를 초래하여 추가적인 균열발생 및 지하수의 주요 공급로 역할을 하게 된다. 본 연구에서는 방사성폐기물 처분연구시설(KURT)을 대상으로 현장실험을 통해 암반변형계수를 측정하였고, 이를 바탕으로 손상대 영역을 세분화하여 FLAC2D를 이용한 전산해석을 실시하였다. 실험결과 KURT 주변에는 측정지점에 따라 0.6~1.8m의 손상영역이 발생하였으며, 손상대 구간의 변형계수 값은 주변 암반 변형계수의 약 40%에 해당하였다. 암반손상대로 인해 KURT 내 터널변위는 약 65%의 추가변위가 발생하였고, 최대 주응력은 58% 감소되었음을 확인하였다. 또한 손상대 영역의 고려로 인해 터널의 좌 우측 하단부에 발생되었던 소성 영역이 터널의 천정 및 바닥부근으로 확대되는 경향을 보였다.

• 지구물리와물리탐사
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• 제11권4호
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• pp.350-360
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• 2008

전기비저항은 땅의 여러 물리적 특성 중의 하나로 전기비저항 탐사, 전기비저항 검층과 실내시험 등을 통해 측정된다. 최근에 전기비저항은 도로나 철도터널의 지보형식 설계에서 미시추구간의 암반등급을 예측하는데 활용되는 등 그 활용도가 증가하고 있다. 전기비저항으로부터 신뢰할 수 있는 암반등급을 추정하기 위해서는 많은 현장시험과 함께 전기 비저항과 암반분류의 상관성에 대한 고찰이 요구된다. 본 연구에서는 먼저 암석시료에 대해 탄성파속도, 탄성계수, 일축 압축강도 등의 암석물성시험과 전기비저항 코어시험을 실시하였다. 시험결과로부터 획득된 전기비저항과 암석물성의 상관성을 분석한 결과 전기비저항이 암석물성과 높은 상관성을 가지고 있음을 확인하였다. 다음으로 일반적인 지반조사에 비해 현저히 많은 12개의 시추공에서 전기비저항 검층을 실시하여, 전기비저항 탐사 및 전기비저항 검층에 의한 전기비저항과 RMR의 상관성을 고찰하였다. 전기비저항 검층은 RMR과 80% 이상의 매우 높은 상관성을 보여 전기비저항을 이용하여 암반등급을 결정하는 방법이 과학적으로 타당하다는 것을 확인하였다. 이에 반해 전기비저항 탐사는 RMR과 20% 내외의 낮은 상관성을 가지는데 이는 단층파쇄대와 같은 저비저항 이상대가 역산에 영향을 미치기 때문으로 상관관계 분석시 신선한 암반, 절리파쇄대, 단층파쇄대로 그룹을 분리하여 상관성을 분석하면 신뢰성 있는 상관식을 도출할 수 있음을 확인하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1991년도 추계학술발표회 논문집 지반공학에서의 컴퓨터 활용 COMPUTER UTILIZATION IN GEOTECHNICAL ENGINEERING
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• pp.216-232
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• 1991

This Finite Element Program(TAFEM) has been developed to be able to carry out the structural analsis of tunnel section and simulate the surrounding ground behaviour due to New Austrian Tunnelling Method, of which main support is the surrounding ground, itself. The Elasto-plastic theory has been applied. The used finite elements are 8-noded isoparametric element(rock & shotcrete), 2 or 3-noded rod element(rock bolt) and infinite boundary element. The load incremental method and tangential stiffness method has been used. Associated flow rule was applied to plastic flow and yield criteria inclued not only Mohr-Coulomb but also Drucker-Prager. In this paper, Drucker-Prager yield criterion has been used. The relationship between plastic strain and stress is based on the incremental strain concept and stress-strain equation on the basis of the stress path of each gauss point has been adopted. It may be rational that rock is considered to be no-tension material, so that no-tension analysis has been adopted in accordance with the brittle fracture constitutive equation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.14-25
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• 2010

The Yi Sun-Sin grand bridge is the suspension bridge which connects Myodo and Gwangyang. It is over the main navigation channel of Gwangyang Harbor. South anchorage(AN1, Myodo side) of the bridge is designed as rock anchored type. It sustains using the resistance of the underground rock's mass in Myodo. As this type of anchorage can minimize the exposure of the structure, It is economically efficient and environmentally friendly. North anchorage (AN2, Gwangyang side) is designed as the gravity type. This anchorage is 68 meters in diameter and use its own weight to support. Instead of normal rectangular diaphragm wall, the circular shape diaphragm wall is adopted to the north anchorage. It doesn't need to use internal temporary facilities, so it can significantly improve the constructability of the structure.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.122-128
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• 2003

Rock bolts are widely used as a supplementary roof support system in hard-rock mining since a long time. Since the performance of fully grouted passive bolts depends on bond strength, in the present investigation extensive laboratory pull-out as well as push-out tests were conducted varying the bolt diameter, length and cement-water mixing ratios of grout. The load-displacement curves were developed and were verified with the numerical results obtained from finite element analysis using ALGOR software. Numerical models were validated for push-out tests and a detailed analysis was carried out to know the displacement, stress, strain distribution along the bolt.

• 터널과지하공간
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• 제5권1호
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• pp.11-21
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• 1995

일반적으로 NATM공법에서 지보의 설계는 암반반응곡선의 개념을 통해 수행된다. 그러나 암반반응곡선은 암질이 좋고 과지압에 의한 문제가 심각하지 않은 지역에 적용되며, 따라서 주로 불연속면에 의해 암반의 거동이 영향을 받는 지역에서는 시공과정에 직접 적용하기가 힘들다. 본 연구에서는 암반 블록에 대한 블록반응곡선을 연구하여, 블록반응곡선상에서 지보를 설계하였다. 각각의 차분시각에서의 변위와 응력을 얻기위해서 개별요소 프로그램인 UDEC을 사용하였다. 블록은 Mohr-Coulomb 모델이며, 불연속면은 Barton-Bandis 모델이다. 블록과 불연속면의 물성은 실험실 실험을 통하여 구하였다. 블록반응곡선을 이용한 지보설계과정을 이해하기 위하여 간단한 모델분석을 실시하였다. 동일한 형상의 키블록이 공동의 천장, 측벽, 바닥에 존재할 경우, 각 블록의 안정성 판단 및 지보의 설계를 실시하였다. 또한 초기지압의 영향을 알아보기 위하여, 측압계수(K)를 달리하여 해석해보았다. 현재 건설중인 공동에 대한 안정성 판단 및 지보설계를 블록반응곡선을 이용하여 설계하였다.

• Acta Via Serica
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• 제6권2호
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• pp.21-36
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• 2021

This paper discusses textile motifs depicted in the hunting panels inside the late Sasanian larger grotto at Taq-i Bustan. Scholars of Iranian art have referred to these rock reliefs in order to trace the origin of Sasanian textile decorations and their exportation in the whole medieval Eurasian continent. This however does not seem to be the case. In fact, the textile motifs reproduced at Taq-i Bustan could be a good term of comparison only for late Sasanian textile production. Moreover, nothing like this has appeared in previous Sasanian rock reliefs. For this reason, the present paper argues that some of those motifs could actually be importations from Central Asia where reproductions of textiles embellished with those motifs were very popular. Islamic written sources on Taq-i Bustan rock reliefs could be very useful to support some ideas expressed in this paper.

• Geomechanics and Engineering
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• 제29권3호
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• pp.219-228
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• 2022

The most widely used parameter to represent rock abrasiveness is the Cerchar abrasivity index (CAI). The CAI value can be applied to predict wear in TBM cutters. It has been extensively demonstrated that the CAI is affected significantly by cementation degree, strength, and amount of abrasive minerals, i.e., the quartz content or equivalent quartz content in rocks. The relationship between the properties of rocks and the CAI is investigated in this study. A database comprising 223 observations that includes rock types, uniaxial compressive strengths, Brazilian tensile strengths, equivalent quartz contents, quartz contents, brittleness indices, and CAIs is constructed. A linear model is developed by selecting independent variables while considering multicollinearity after performing multiple regression analyses. Machine learning-based regression methods including support vector regression, regression tree regression, k-nearest neighbors regression, random forest regression, and artificial neural network regression are used in addition to multiple linear regression. The results of the random forest regression model show that it yields the best prediction performance.

• Geomechanics and Engineering
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• 제19권6호
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• pp.485-498
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• 2019

Pre-tensioned rock bolts can be classified into fully anchored, lengthening anchored and point anchored bolts based on the bond length of the resin or cement mortar inside the borehole. Bolts in varying anchoring methods may significantly affect the supporting effect of surrounding rock around a tunnel. However, thus far, the theoretical basis of selecting a proper anchoring method has not been thoroughly investigated. Based on this problem, 16 schemes were designed while incorporating the effects of anchoring length, pretension, bolt length, and spacing, and a systematic numerical experiment was performed in this paper. The distribution characteristics of the stress field in the surrounding rock, which corresponded to various anchoring scenarios, were obtained. Furthermore, an analytical approach for computing the active and passive strengthening index of the anchored surrounding rock is presented. A new fully anchoring method with pretension and matching technology are also provided. Then, an isolated loading model of the anchored surrounding rock was constructed. The physical simulation test for the bearing capacity of the model was performed with three schemes. Finally, the strengthening mechanism of varying anchoring methods was validated. The research findings in this paper may provide theoretical guidelines for the design and construction of bolting support in tunnels.

• Geomechanics and Engineering
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• 제22권4호
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• pp.277-290
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• 2020

This paper presents an elastic-plastic solution for the circular tunnel of elastic-strain softening behavior considering the pressure-dependent Young's modulus and the nonlinear dilatancy. The proposed solution is verified by the results of the field measuring and numerical simulation from a practical project, and a published closed-form analysis solution. The influence of each factor is discussed in detail, and the ability of Young's modulus and dilatancy characterizing the mechanical response of surrounding rock is investigated. It is found that, in low levels of support pressure, adopting the constant Young's modulus model will seriously misestimate the surrounding rock deformation. Using the constant dilatancy model will underestimate the surrounding rock deformation. When adopting the constant dilatancy model, as the dilation angle increases, the range of the plastic region increases, and the surrounding rock deformation weakens. When adopting the nonlinear dilatancy, the plastic region range and the surrounding rock deformation are the largest. The surrounding rock deformation using pressure-dependent Young's modulus model is between those resulted from two constant Young's modulus models. The constant α of pressuredependent Young's modulus model is the main factor affecting the tunnel displacement. The influence of α using a constant dilatancy model is much more apparent than that using a nonlinear dilatancy model.