• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.573-576
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• 2008

절토사면 및 천심도 터널의 경우 불연속면을 따른 블록의 미끄러짐 및 회전 등이 안정성에 큰 영향을 미친다. 국도나 지방도 등을 확장 공사함에 따라 산악이 많은 우리나라 지형의 특성상 절토사면이 많이 발생하게 되고, 경우에 따라서는 이러한 절토사면에 터널이 위치하게 된다. 이런 상황의 터널갱구부 및 인접한 절토사면부에서 붕괴 및 균열이 빈번하게 발생되고 있다. 본 연구에서는 대절토사면과 인접한 터널갱구부에 대하여 편토압이 균열의 주원인인지를 결정하기 위하여 변위 및 응력 패턴을 분석한 사례연구를 제시하였다. 조사대상지역은 울진군에 위치한 터널굴진 현장이고, 붕괴는 터널갱구부와 인접한 절토사면부에서 발생하였으며 터널갱구부 상단의 숏크리트 타설지역에서 다수의 균열이 관찰되었다. 언급한 터널갱구부의 변위 및 응력패턴을 모사하기 위하여 유한차분법에 근거한 플랙을 사용하였으며, 세밀한 수치해석을 위해 편재절리모델을 도입하였다. 마지막으로, 터널갱구부의 균열에 영향을 미친 주원인에 대한 고찰을 다루었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.536-549
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• 2005

국내 대부분을 차지하고 있는 NATM의 주요원리는 주변지반의 지보효과를 활용하는 터널굴착공법이다. 따라서 실제 지반조건이 원설계조건 보다 역학적으로 불량한 경우 보강공법의 적용은 필수적이라 할 수 있으나, 합리적인 설계변경은 현실적으로 쉽지 않은 실정이다. 또한 현실적인 이유로 양방향으로 터널을 관통하는 설계법과 달리 종종 1방향 굴진으로 터널을 관통하는 경우가 있다. 그러나 이러한 1방향 굴진은 불가분 굴진 종점부에서 저토피 갱구를 향하게 되므로, 지반이 연약한 경ㅇ우 막장 붕괴의 위험이 매우 높은 것으로 알려져 있다. 본 터널은 설계 시 갱구부 지반을 풍화암과 연암으로 보고 설계 하였으나, 실제 굴착 시 확인된 지층은 핵석을 포함한 실트질모래(SP-SM)로 판명되었다. 더구나 터널굴진 방향에 있어서도 양방향 굴착이 아닌 저토피 갱구를 향한 1방향 굴진을 실시하였으며, 이러한 시공 중에 터널관통을 불과 19m 남겨둔 갱구부에서 막장부괴와 동시에 상부사면 함몰이 발생하였다. 본 연구는 토사터널 갱구부 1방향 굴진 시 발생한 막장붕괴 보강사례로서, 지상보강(시멘트밀크 그라우팅)과 갱내보강(방사상 FRP보강그라우팅) 그리고 인버트폐합을 실시하여 성공적으로 터널시공을 완료한 사례연구이다. 본 사례는 향후 토사터널 갱구부의 설계와 시공에 유용한 참고자료가 될 것이다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.3
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• pp.625-639
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• 2018

This study is about the reinforcing type of reinforcement method which is reinforced in tunnel portal of tunnel with bad ground condition. Generally, it is known that the horizontal reinforcement method is more effective than the conventional reinforcement method. However, as a limitation of the tunnel construction technology, it is being constructed by the superposition reinforcement method. In recent years, high-strength large-diameter steel pipes and horizontally oriented longitudes (L = 30.0~50.0 m) construction technology have been developed. Therefore, it is required to study reinforcement method of tunnel portal reinforcement method. Therefore, 3-D numerical analysis (Midas GTS NX 3D) was performed by setting the reinforcement method (No reinforcement type, overlap reinforcement type and horizontal reinforcement type) and ground condition as parameters. As a result, it was considered that the reinforcement effect was the largest as the horizontal reinforcement type of the reinforcement method was the smallest in the displacement and the support material stress. Based on the results of the numerical analysis, horizontal steel pipe grouting was applied to the actual tunnel site. The displacement of the tunnel portal and the stress of the support material occurred within the allowable values and were considered to ensure sufficient stability.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2004.04a
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• pp.199-217
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• 2004

터널 설계에 있어 갱구부의 위치 및 갱문형식의 선정은 터널 및 갱구사면의 안정성뿐만 아니라, 주위환경과의 조화 및 자연환경 훼손 최소화 등과 같은 환경적인 측면에서도 매우 중요한 부분이다. 현행 국내의 경우 경제성과 시공성 위주의 갱구부 위치 선정으로 과다 절취구간이 발생되어 환경훼손, 민원문제 발생, 과다한 용지 매입비용 등의 여러 가지 부작용이 발생되고 있다. 또한, 갱문 형식의 선정에 있어서 갱구부의 지형여건 및 제반 환경적 영향을 고려하지 않고 원통절개형과 면벽식 갱문의 획일적인 적용으로 주변지형과의 부조화를 이루는 사례가 다수 발생하고 있으며, 갱구부 상단의 유실된 토석이 완충공간의 부족으로 도로 노면상에 낙하되는 사고가 발생하고 있어 그에 대한 대책이 필요한 실정이다. 이와 같은 문제점을 보완하기 위해 갱구부 절취구간 최소화를 위한 구체적인 최소토피고 기준을 마련하였으며, 갱구상단 지형경사의 완급, 갱문주위의 배수기능, 낙석${\cdot}$산사태 등의 발생가능성 등을 고려한 새로운 갱문형식을 제안하고 체계적인 검토를 수행하였다. 이를 통해 점차 강화되는 환경보호정책 방향에 부응하고 자연환경 훼손을 최소화하며, 특히 해빙기와 집중호우시 낙석${\cdot}$눈사태로부터 도로의 안전을 확보할 수 있는 터널 갱문부 설계기준을 제시하였다. 또한, 실제 고속도로 터널의 설계 적용사례를 통하여 본 설계기준의 적용성을 분석하였으며, 실제 갱문 시공사례를 소개하여 향후 설계 및 시공에 도움이 되고자 하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.3-10
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• 2000

The compression wave produced when a high-speed train enters a tunnel propagates along the tunnel ahead of the train. The micro pressure wave related to the compression wave is a special physics phenomena created by high-speed train-tunnel interfaces. A among methods for the purpose of reducing the micro pressure wave is to delay the gradient of the compression wave by using aerodynamic structures. The objective of this paper is to determine the optimum slanted portal using the moving model rig. According to the results, the maximum value of micro pressure wave is reduced by 19.2% for the $45^{\circ}$ slanted portal installed at the entrance of the tunnel and reduced by 41.9% for the $45^{\circ}$ slanted portals at the entrance and exit of the tunnel. Also it is reduced by 34.6% for the $30^{\circ}$ slanted portals installed at the entrance and exit of the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.50-61
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• 2000

The ground around the portal of a tunnel is the most typical part showing the 3-dimensional mechanical behavior in the tunnel. The portal slope is constructed at the weathered soft rock-mass, and remains as a potential sliding mass. The slope failure around the tunnel portal may happen drastically and induce the great disaster; hence, for the permanent stability several special techniques are required. To solve this problem, the ground around the tunnel portal may be excavated in the arch shape to develop the arching effect in horizontal direction. With the arch-type portal slope, one can reduce considerably the excavation mass and the damage of environments. This approach has not been attempted yet due to the lack of understanding and the well-defined analyzing method, so the retaining wall type portal is more universal. The 3-dimensional finite element analyses were carried out to prove that the arch type is more advantageous in safety and cost than the right angle type. The influence of the tunnel construction sequence and the strength of the rock-mass on the slope stability was investigated by focusing on the maximum shear strain in the slope, and the yield zone at the tunnel face.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.213-225
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• 2004

The number of tunnels are in fact increasing as a part of linear improvement project of general national highway and road enlargement and pavement project. Recently, collapses of portal slope are also occurring considerably, due to local raining from severe rain storm and abnormal weather. Accordingly, it was risen a necessity to efficiently respond to tunnel portal slope damage and maintenance in Korea and oversea nations. This paper is a basic proposal to execute a survey on the current status and state of the tunnel portal slopes that were already installed and are now being operated along general national highways, and also to execute state evaluation for the purpose of managing those effectively. As a research method, domestic tunnels were analyzed in accordance with geometrical shape such as access type, portal form, and tunnel type, etc. via field survey to analyze the types of tunnel portal slopes along national highways. State evaluation classification sheet is presented to divide classes for the danger state of the surveyed portal slopes, and then the related grades are divided. It is mainly aimed at classifying the tunnel portal slope along national highways with using this state evaluation, to use it as basic data so that continuous maintenance can be executed in the future in accordance with danger classes.

• Explosives and Blasting
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• v.26 no.2
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• pp.38-44
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• 2008

Recently, planning road construction in South Korea is focused on upgrading of the existing road by rerouting or restructuring. For this, roads under current construction in Korea go for more straight in its alignments and routing. Straight routing makes it all the more required to construct many mountain tunnels and bridges in Korea where mountains are so widely spread. Some portal of mountain tunnel is not rarely planed at high steep slope of mountain valley where it is not easy to secure working space for tunnel excavation. Reverse excavation is an alternative measure for excavation of tunnel portal at high steep slope. Construction in reverse excavation method has three important points requiring careful consideration: 1)planning of pilot tunnel in proper width, height, and length etc., 2)measure against the effect of one-side earth pressure to the direction of tunnel portal, 3)securing tunnel safety against shallow ground condition at portal zone. This paper intends to suggest applicable range of pilot tunnel for reverse excavation at the portal zone located at high steep slope, and shows result of study on the appropriateness of a reverse excavation by means of 3D numerical analysis. Result of 3D numerical analysis for reverse excavation at high steep slope shows that pilot tunneling will be applicable to start from the point $20{\sim}25m$ before the portal from inside the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.569-579
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• 2016

In order to ensure the stability of tunnel portal slope, reinforcement method such as anchors, soil nails and rock bolts have been used in Korea. When selecting slope reinforcement methods in tunnel portal area such as reinforcement arrangement and length, trial and error method can be very time-consuming and it was also not easy to verify the selection of an optimum condition. In this study, using the FISH language embedded in the finite difference code FLAC3D program, the optimization technique was developed with the Differential Evolution Algorithm (DEA). After building a database on the soil nailing method in tunnel portal area, this system can be selected to an optimum arrangement plan based on the factor of safety through the FLAC3D analysis. Through the results of numerical analysis, it was confirmed that the number of analysis was decreased by about 8 times when DEA based optimization technique was used compared to the full combination (FC). In case of the design of slope reinforcement in tunnel portal area, if this built-system is used, it is expected that the selection of an optimum arrangement plan can be relatively easier.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.4
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• pp.387-400
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• 2013

In this study, the slope stability analysis and the landslide hazard assessment in tunnel portal slope were carried out. First, we selected highly vulnerable areas to slope failure using the slope stability analysis and analyzed the slope failure scale. According to analyses results, high vulnerable area to slope failure is located at 485~495 m above sea level. The slope is stable in a dry condition, while it becomes unstable in rainfall condition. The analysis results of slope failure scale show that the depth of slope failure is maximum 2.1 m and the length of slope failure is 18.6 m toward the dip direction of slope. Second, we developed a 3-D simulation program to analyze characteristics of runout behavior of debris flow. The developed program was applied to highly vulnerable areas to slope failure. The result of 3-D simulation shows that debris flow moves toward the central part of the valley with the movement direction of landslide from the upper part to the lower part of the slope. 3-D simulation shows that debris flow moves down to the bottom of mountain slope with a speed of 7.74 m/s and may make damage to the tunnel portal directly after 10 seconds from slope failure.