• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.2
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• pp.193-205
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• 2008

The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.

• Tunnel and Underground Space
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• v.10 no.2
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• pp.249-256
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• 2000

According to the industrial restructuring in the late 1980's, most domestic mines have been shutdown or suspended in operation. The closed underground excavation caverns remain in their abandoned conditions, and they will potentially cause environmental hazards. To evaluate the feasibility of the utilization of the abandoned caverns, the foreign crises were studied. As a result, we proposed several possible examples including underground storage cavern fur food products, underground compressed air energy system(CAES), and underground repository (or incineration plant) of industrial wastes. Among them, the underground waste repositories are most probable to be seen in Korea in the near future. For this, the study in rock engineering aspects should be conducted, which will include the establishment of support system and safety measure of the abandoned underground excavation caverns.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.13-24
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• 2000

The collapse shapes and causes of tunnel in the highway were analyzed and reinforced methods of tunnel were investigated in the paper. Collapse shapes of tunnel are divided into three types such as subsurface failure, small scale wedge failure and slickenside strata failure. These three shapes consist of 35%, 50%, and 15%, respectively. The 85% of collapse was located near the entrance and exit of tunnel. The 15% was located at the intersection of emergency laybys. When tunnel collapses are analyzed by the failure concept, sliding failure amounts to more than 83%.

• The Journal of Engineering Geology
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• v.10 no.1
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• pp.79-93
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• 2000

When caverns are excavated, it is very important to understand the distribution and charateristics of geological structures because the structures have an significant effect on grouting, rock reinforcement, and groundwater flow, etc. The main water bearing fractures have an orientation of N50~60W and these fractures are known as tension fractures. Their orientation coincides with a long elliptical axis ofpumping test, and they cross the tension fractures of N10~30E. They have typical fracture systems ofrhombic type in this area.

• Tunnel and Underground Space
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• v.5 no.2
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• pp.104-113
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• 1995

Shear strength of the discontinuity on which the pre-failure of rock slope was occurred during surface excavation was measured through the direct shear test using core samples obtained in-situ. Internal friction angle was increased as the roughness of discontinuity surface(JRC) was increased. Results of the tilt test using core samples of higher JRC also showed very similar trend as those of the direct shear test. When the samples replicated from natural cores were used int he tilt test, results of friction angles showed almost perfect continuation of the residual friction angles from the direct shear test. However, when the gouge material existed in the discontinuity the internal friction angle strongly depended upon the rate of filling thickness to the height of asperity irrespective of the JRC. Based on the results of both direct shear test and tilt test internal friction angle and cohesion of discontinuity, which reflect the in-situ conditions fo pre-sliding failure and also can be used for the optimum design of support system, were assessed. Two kinds of support measures which were expected to increase the stability of rock slope were considered; lowering of slope face angle and installation of rock cable. But, it was found that the first method might lead to more unstable conditions of rock slope when the cohesion of discontinuity plane was negligibly low and in that case the support systems of any kind which could exert actual resisting force were needed to ensure the permanent stability of rock slope.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.51-61
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• 2016

New building methods are needed to aid increased inner-city redevelopment and industrial construction. A particular area of improvement is the efficient use of cut slopes, with the minimization of associated problems. A retaining wall of precast panels can resist the horizontal earth pressure by increasing the shear strength of the ground and reinforcing it through contact with the panels. Precast panels allow quick construction and avoid the problem of concrete deterioration. Other problems to be solved include the digging of borrow pits, the disposal of material cut from the slope, and degradation of the landscape caused by the exposed concrete retaining wall.This study suggest the methods of improvement of an existing precast panel wall system by changing the appearance of the panels to that of natural rock and improving the process of adhering the panel to a vertical slope. The panels were tested in the laboratory and in the field. The laboratory test verified their specific strength and behavior, and the field test assessed the panels' ground adherence at a vertical cutting. Reinforcement of the cutting slope was also measured and compared with the results of 3D numerical analysis. The results of laboratory test, identified that the shear bar increase the punching resistance of panel. And as a results of test construction, identified the construct ability and field applicability of the panel wall system adhered to in-situ ground. In addition to that, extended measurement and numerical analysis, identified the long-term stability of panel wall system adhered to in-situ ground.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.296-296
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• 2008

국내 절토비탈면은 이상 기후 및 건설공사의 증대로 인해 증가하고 있는 추세이며 장마철 및 태풍으로 인해 비탈면의 붕괴로 많은 인명 및 재산피해가 발생되고 있는 실정이다. 국내에서 사용되고 있는 기존의 비탈면의 설계기준은 암반의 불연속면에 대한 조사를 실시하고는 있지만 주로 암반의 굴착난이도를 토층, 리핑암, 발파암으로 구분하여 각각의 비탈면 절취경사를 결정하여 사용하는 방법을 사용하였으며 이러한 기준은 단순히 암석의 강도를 기준으로 설정되어 있으므로 암석의 공학적 특성 즉, 암반내 불연속면 방향성, 연속성, 충진물질, 마찰각, 풍화속도 등의 영향으로 공용후 비탈면 구배의 재조정 및 보강이 빈번하다. 국내외 절토비탈면의 설계기준은 각 기관별로 산재되어 있었으며 비탈면에 대한 설계 및 시공 등에 관한 기준은 도로와 철도 설계기준에 일부 반영되어 있을 뿐 항만, 댐, 택지조성 등 기타 시설 설계기준에는 비탈면에 대한 기준이 마련되어 있지 않아 표준적인 비탈면 설계기준 및 유지관리지침이 등이 필요하였다. 이러한 문제점을 보완하기 위해 2004년부터 2006까지 한국시설안전공단, 한국도로공사, 대한주택공사가 협동으로 연구한 건설공사 비탈면 설계 시공 및 유지관리에 관한 연구의 결과로 2006년도에 "건설공사 비탈면 설계기준"이 수립되었다. 이 설계기준은 건설공사에서의 기존 상이한 기준들을 정리하고 동일화하는 작업을 수행하였으며 지반의 조사에서부터 대책공까지를 막나하여 정리하였다. 그러나 최근에 급격한 기후변화로 인한 비탈면붕괴 빈번함에 따라 과거 적용되어 왔던 이들 기준을 적용하는 경우, 특히 상부 토층 및 풍화암 구간에서 많은 설계안전율을 만족하지 못해 많은 보강을 수반해야 하는 문제가 발생되고 있어 그 원인에 대한 분석을 수행하고자 하였다. 2006년도 정리된 기준은 과거에 적용하여 온 유기시의 안전율 조건을 Fs > 1.1~1.2을 적용하였던 것을 Fs > 1.2로 통일하였으며 지하수위 조건은 지표면에 위치하도록 하였다. 지하수위 조건은 풍화암 및 토층의 경우, 과거 지표면에 -3m를 적용한 시기가 있었으나 지표면에 지하수위를 적용하는 것이 일반적인 해석방법이다. 이러한 결과의 원인을 검토해 보면 다음과 같다. 첫째, 풍화암 및 토층에 적용되어 온 지반강도 정수가 과거 적용한 값보다 최근에는 작아지는 경향을 보이고 있다. 둘째, 지하수위 적용문제로 현재 지표면에 지하수위를 두어 안전율을 감소시키는 문제로 이는 최근 들어 많은 연구기관에서 강우시 간극수압의 증가에 대한 연구가 활발하게 진행되고 있다. 그러나 침투수 해석은 현행 기준에도 강우의 침투를 고려한 해석을 실시하는 경우 FS > 1.3 적용하는 것으로 되어 있으나 대부분의 해석에서는 적용이 되지 못하고 있는 실정이다. 셋째, 안전율이 과거에 주로 적용된 Fs > 1.1에서 Fs > 1.2로 상향 조정되어 우기시의 설계안전율 만족시키지 못하는 문제이다. 그러므로 이러한 문제점을 개선하기 위한 검토가 필요하며 장기적으로 이에 대한 합리적인 기준을 개정하는 작업이 추후에 수행되어야 할 것으로 판단된다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.2
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• pp.181-186
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• 2022

Dam slope RIM is a highly important contact interface where the main body and the base surface are connected. In general, when the grouting for the slope of the dam structure is designed, it is planned using limited data (drilling, geological map, etc.). This makes it very difficult to accurately consider the original ground characteristics of the slope RIM grouting target, In addition, when the grouting volume planned during the design is drilled and injected into the original ground where the waterstop is secured, there is a possibility that the original ground with the waterstop is disturbed and the effect of the waterstop is rather diminished. In order to overcome such problems, it is more suitable to first consider geological conditions and determine whether to perform optimal grouting on the original ground through on-site repair tests before performing RIM grouting. In this paper, to determine the grouting of the RIM unit, a pilot hole water pressure test was performed on the rock of the slope in the target section. The analysis shows grouting volume of 1 Lugeon or less, and the cement injection amount also shows the injection result of 1 kg/m or less. In this case, performing grouting is rather counterproductive. This result can be evaluated through a rock of which some degree of order of mass is secured, as it is a dam design standard of 1 Lugeon or less when analyzed, using the results of visual observation and geological map creation during slope cutting. Therefore, in conclusion, it is preferable to make the decision for using RIM grouting on the slope of the dam body structure, based on 1 Lugeon in a rock state, and the cement injection amount also at 1 kg/m.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.6-19
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• 2003

This study has for its object to increase an objectivity of the observation result in the face mapping of tunnel and to suggest the reasonable support and reinforcement methods to be considered the rock properties. It was developed in this study to the tunnel stability evaluation system(Prototype NFEST) to be used fuzzy set theory and neuro-fuzzy techniques, and this system was verified according to the reliability evaluation between the 36 learning data and the inferred results. When it summarized the results; (1) 12 evaluation items and ranges were proposed to be modified basis on the RMR which are well known to the domestic workers. (2) It was shown that correlation coefficient(│R│) between $RMR_{inf}$ inferred by 12 items and $RMR_{org}$ due to arithmetic total, $RMR_{chk}$ due to subjective judgement of observer are relatively high relationship with each 0.83 and 0.79. (3) Inferred result of the total tunnel safety shows also a good relationship with $RMR_{inf}$ (│R│=0.7) and the rock weathering(│R│=0.84).

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.4
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• pp.341-354
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• 2016

This article is to apply the tunnel support system selected after comparatively analyzing of RMR and tunnel instrumentation between the tunnel behavior characteristic predicted through geotechnical investigations and the numerical analysis at the design stage and the properties deformation occurred at the construction stage. This attempt results from the behavior characteristic of the tunnel excavation ground shown differently in accordance with the ground quality and reinforcement method. This, therefore, provide the data and results analysed the actual decision RMR-crown settlement & convergence and reduction of material property of ground as parameters. Also, it's shown that the tunnel designer is able to predict tunnel behavior characteristic when designing in bedrock areas excessively distributed faults and fractured zones.