초록

Abstract

Traffic jam and congestion in urban areas has caused the need to improve the utility ofunderground space. In response, research on underground structures is increasinglybeing conducted. Notably, a double-deck tunnel is one of the most widely used of allthose underground structures. This double-deck tunnel is separated by the middle slabinto the upper and lower roadways. Both vehicle load and earthquake load cause themiddle slab to exhibit dynamic behavior. Earthquake-related response characteristics,in particular, are highly complex and difficult to interpret in a theoretical context, andthus experimental research is required. The aim of the present study is to assess thestability of a double-deck tunnel’s middle slab of the Collapse Prevention Level andSeismic Category 1 with regard to the presence of vibration-damping Rubber Bearings. In vibration table tests, the ratio of similitude was set to 1/4. Linings and vibratingplatforms were fixed during scaled model tests to represent the integrated behavior ofthe ground and the applied models. In doing so, it was possible to minimize relativebehavior. The standard TBM cross-section for the virtual double-deck tunnel wasselected as a test subject. The level of ground motion exerted on the bedrock was setto 0.154 g (artificial seismic wave, Collapse Prevention Level and Seismic Category 1). A seismic wave with the maximum acceleration of 0.154 g was applied to the vibrationtable input (bedrock) to analyze resultant amplification in the models. As a result, theseismic stability of the middle slab was evaluated and analyzed with respect to thepresence of vibration-damping rubber bearings. It was confirmed that the presence ofvibration-damping rubber bearings improved its earthquake acceleration dampingperformance by up to 40%.

초록

도시지역의 교통난 해소와 녹지공간의 확보를 위해 도심지 터널이 증가하면서 차량의 정체 가능성이 높은 터널에 대한제 ․ 배연방식으로 대배기구에 의한 집중배기방식의 적용이 증가하는 추세에 있다. 집중배기방식의 배연성능은 배연풍량 뿐만 아니라 배기구(댐퍼)의 형상이나 배기풍속 등 다양한 인자에 의해서 영향을 받는 것으로 알려져 있다. 이에 본 연구에서는 각국의 배연시스템 설계기준 및 설치현황을 알아보고 배연풍량이 동일한 경우에 배연댐퍼 사이즈에 따른 배연성능을 연기 이동거리 측면에서 수치시뮬레이션을 수행하여 비교 ․ 평가하였으며, 다음과 같은 결과를 얻었다. 배연댐퍼의 단면적이 증가할수록 배기팬에 근접한 댐퍼에서 배기풍량이 집중되어 화재 하류의 댐퍼의 배연풍량이 감소하여 하류측의 연기 이동거리가 증가하는 현상이 발생한다. 이와 같은 현상을 방지하기 위해서는 배연댐퍼의 단면적을 작게하여통과풍속을 높게 함으로써 댐퍼통과 시 압력손실이 증가하도록 하여 배기구간에서 배연풍량의 불균일성을 완화할 필요가 있다. 본 해석범위에서는 배연댐퍼의 설치간격이 50 m인 경우에는 설계통과풍속이 4.4 m/s (댐퍼면적: 2.34 m2 =1.25 × 1.85 m) 이상, 댐퍼의 설치간격이 100 m인 경우에는 설계통과풍속이 4.84 m/s (댐퍼면적: 3.38 m2 = 1.5 × 2.25m) 이상일 때 배연성능확보에 유리한 것으로 나타났다.

Abstract

In order to resolve traffic problems in urban areas and to increase the area of greenspaces, tunnels in downtown areas are being increased. Additionally, the applicationof large port smoke extraction ventilation systems is increasing as a countermeasureto smoke extraction ventilation for tunnels with high potential for traffic congestion. It is known that the smoke extraction performance of the large port smoke extractionsystem is influenced not only by the amount of the extraction flow rate, but also byvarious factors such as the shape of the extraction port (damper) and the extractionair velocity through a damper. Therefore, in this study, the design standards andinstallation status of each country were investigated. When the extraction air flow ratewas the same, the smoke extraction performance according to the size of the damperwas numerically simulated in terms of smoke propagation distance, compared andevaluated, and the following results were obtained. As the cross-sectional area of thesmoke damper increases, the extraction flow rate is concentrated in the damper closeto the extraction fan, and the smoke extraction rate of the damper in downstreamdecreases, thereby increasing the smoke propagation distance on the downstream side. In order to prevent such a phenomenon, it is necessary to reduce the cross-sectionalarea of the smoke damper and increase the velocity of passing air through the damperso that the pressure loss passing through the damper increases, thereby reducing thenon-uniformity of smoke extraction flow rate in the extraction section. In this analysis,it was found that when the interval distance of the extraction damper was 50 m, the airvelocity passing through damper was 4.4 m/s or more, and when the interval distance of the extraction dampers was 100 m, the air velocity passing through damper was greater than 4.84 m/s, it was foundto be advantageous to ensure smoke extraction performance.

초록

Abstract

This paper presents the seal material mixing ratio of tunnel umbrella arch reinforcementmethod. Currently, there is no clear standard for the proper gelation time and curingtime of the Seal material in Korea, and the quality control is also difficult because itcannot be verified. In response, the ratio of the mixture of the seal material wascomposed of four types of indoor experiments, and the amount of gelation time andbleed was checked. In addition, a non-cart penetration test confirmed the curing timeand compared the ratio of each combination. Further experiments on W/C 120%identified the effect of mixing speed and time on the seal material. A total of three fieldexperiments were conducted based on indoor experiments, and the size and strength ofbulb formation were compared by checking the curing time of the specimen and maininjection. Comparisons show that the lower W/C, the stronger the strength, the largerthe size of the bulb, and the faster the hardening time appears. Based on the results ofthe gelation time and curing time, it was deemed that the mixing ratio of W/C 120%is most appropriate when applied to the actual site.

초록

디스크커터의 간격을 최적화하는 것은 TBM 커터헤드의 설계의 핵심요소로, TBM의 굴진성능을 좌우한다. 실대형 선형절삭시험은 디스크커터의 간격 산정을 위해 가장 신뢰성 및 정확도가 높은 시험으로 알려져 있으나 실대형 실험을 위해 경제적 및 시간적 비용이 소요되는 단점이 있다. 본 연구에서는 개별요소법 기반의 수치해석 연구를 통해 암반의 일축압축강도 및 압입깊이에 따른 비에너지-S/P비 간의 경향성을 분석하였고, 17인치 디스크커터의 최적 간격을 도출하였다. 수치해석모델의 적정성을 검토하기 위하여 디스크커터에 작용되는 회전력을 CSM 모델과 비교·검토하였다. 선형절삭시험에 대한 수치해석 결과, 디스크커터에 작용되는 회전력은 CSM 모델의 이론식으로부터 도출한 회전력과 유사한것으로 분석되었다. 5가지(50 MPa, 70 MPa, 100 MPa, 150 MPa, 200 MPa)의 일축압축강도에 대한 수치해석 결과, 암반강도가 증가할수록 디스크커터의 최적간격의 범위는 감소하는 경향을 보였으며 80~100 mm범위에서 최소 비에너지를 보이는 것으로 확인되었다. 이는, 기존에 보고된 디스크커터의 최적 간격과 일치되는 경향으로써, 본 연구를 통해 산정된 디스크커터 간격을 밑받침한다.

Abstract

Optimizing the spacing of the disc cutter is a key element in the design of the TBMcutter head, which determines the drilling performance of the TBM. The full-scalelinear cutting test is known as the most reliable and accurate test for calculating thespacing of the disc cutter, but it has the disadvantage of costly and time-consuming forthe full-scale experiment. In this study, through the numerical analysis study based onthe discrete element method, the tendency between Specific Energy-S/P ratio accordingto uniaxial compression strength and penetration depth of rock was analyzed, and theoptimum spacing of 17-inch disc cutter was derived. To examine the appropriatenessof the numerical analysis model, the rolling force acting on the disc cutter wascompared and reviewed with the CSM model. As a result of numerical analysis for thelinear cutting test, the rolling force acting on the disc cutter was analyzed to be similarto the rolling force derived from the theoretical formula of the CSM model. From thenumerical analysis on 5 UCS cases (50 MPa, 70 MPa, 100 MPa, 150 MPa, 200 MPa),it is found that the range of the optimum spacing of the disc cutter decreases as the rockstrength increases. And it can be concluded that 80~100 mm of disc cutter spacing isthe optimum range having minimum specific energy regardless of rock strength. Thistends to coincide with the optimal spacing of previously reported disk cutters, which underpins the disk cutter spacing calculated through this study.

초록

증가하는 도심지 전철 급행화의 요구에 따라, 완행과 급행철도를 동시에 운영할 수 있도록 하는 부본선의 건설이 필요하다. 그러나 기존 대피선 설치 방안은 열차의 운행을 차단한다는 점에서 긴 공사기간이 필요할 뿐만 아니라 막대한 경제적손실을 발생시키는 문제점이 있다. 이를 개선하고자 기존 지하철 터널 운영 중이라는 특수한 상황에서의 대피선 설치 방안 연구가 필요하며 대피선 건설방안 적용에 따른 시공 리스크 분석 또한 요구된다. 따라서 본 논문에서는 지하철 4호선과천정부청사역을 가상의 대피선 건설 대상역으로 선정하여 최적의 대피선 건설방안을 도출하였으며, 기존 지하철 터널운영 중 대피선 건설 예비 설계단계 시 발생 가능한 리스크 사건에 대한 리스크 식별 및 대응계획 수립, 리스크 평가, 리스크 통제 및 관리의 일련의 리스크 관리 프로세스를 수행하였다. 총 8가지의 발생 가능한 리스크 사건과 리스크 저감 대책을 선정하였으며 5단계의 리스크 사건 발생확률 및 영향도 기준을 활용한 리스크 평가 매트릭스를 구축하여 리스크 및잔류 리스크 평가를 수행하였다. 리스크 평가 결과를 바탕으로 각 리스크 사건의 평가 점수와 리스크 저감 대책공법의 저감효과를 확인하였다.

Abstract

As an increasing demand for rapid railway transportation, the construction of sidetrackis inevitable to operate local and express trains simultaneously. However, the currenttechnologies for the sidetrack construction method require a long construction periodby interrupting the operation of the existing subway line, as well as cause a hugeeconomic loss. Thus, it is necessary to study the sidetrack construction method underthe special situation that the subway is in operation and to analyze the risk of theexisting tunnel enlargement process for the sidetrack construction. Therefore, in thispaper, the Government Complex Gwacheon station on Subway Line 4 was consideredas a target station for the virtual sidetrack construction and the optimal sidetrackconstruction plan was derived. Subsequently, the application of risk managementprocess was carried out in the order of identifying risk, risk response planning,performing a risk analysis, risk monitoring and control for potential risk events duringthe construction of sidetrack under the subway operation. A total of eight potential riskevents and risk mitigation methods were selected, and a risk assessment matrix was established using the five-step risk probability and impact level criteria to perform the risk assessment includingresidual risks. Based on the results of the risk assessment, the risk grade and the reduction effect of each risk mitigationmethod were confirmed.

초록

본 연구에서는 처분장의 장기 건전성 평가모델을 확보하기 위해 한국원자력연구원내 지하처분연구시설의 화강암을 대상으로 심층 처분복합환경을 모사한 암석시편의Mazars 손상모델 상수를 측정하였다. 이를 위하여 실제 처분장 특성을 고려한 3가지온도(15°C, 45°C, 75°C)와 건조/포화 조건에서 일축압축강도 및 간접인장강도 실험을 수행하였다. 최대유효인장변형률, At, Bt, Ac, Bc 등 주요 파라미터들은 콘크리트 대상으로 연구된 참고문헌의 값들과 차이를 보였으며 이는 암석과 콘크리트 시료의 탄성계수 차이 때문으로 판단된다. 시험결과 시료의 포화로 인해 Bt와 Bc의값은 증가하였다. 또한 온도증가로 인해 최대 유효인장변형률과 Bt는 증가하였고 Bc는 감소하는 것을 확인하였다. 본 연구를 통해 도출된 손상모델은 한국원자력연구원 내에서 현재 개발 중인 Coupled Thermo-Hydro-Mechanical Damage수치해석의 손상모델로 이용될 계획이다.

Abstract

In this study, the damage parameters of Mazars model for KURT (KAERI UndergroundResearch Tunnel) granite are measured form uniaxial compressive and Brazilian testsunder the simulated coupled condition of a deep geological disposal. The tests areconducted in three different temperatures (15°C, 45°C, and 75°C) and dry/saturatedconditions. Major model parameters such as maximum effective tensile strain (), At,Bt, Ac, and Bc differ from the typical reference values of concrete specimens. This islikely due to the difference in elastic modulus between rock and concrete. It is foundthat the saturation of specimens causes an increase in value of Bt and Bc while, the risein temperature increases  and Bt and decreases Bc. The damage model obtained fromthis study will be used as the primary input parameters in the development of coupledThermo-Hydro-Mechanical Damage numerical model in KAERI.

초록

복층터널의 분기구간은 터널 형상이 모자 모양의 대단면 구간인 ‘분기 전 확폭구간’과 본선과 분기터널 간 이격이 생기는 ‘분기 후 구간’으로 나눌 수 있으며, 분기 전 확폭구간의 터널 단면이 분기 후 구간의 단면에 비해 매우 크기 때문에 이러한 차이에 따른 굴착 영향이 분기구의 전체적인 굴착 안정성 검토 시 고려되어야 한다. 본 연구에서는 암반에서 시공되는 NATM 방식의 2차로 대심도(40 m) 본선 복층터널에서 1차로 단층터널로 분기가 되는 조건을 대상으로 3차원 유한요소해석을 통해 분기 전 확폭구간 굴착(선행굴착) 시 굴착공법과 벤치길이 변화에 따라 선행굴착이 분기 후 구간의 굴착 안정성에 미치는 영향을 검토하였다. 그 결과, 굴착공법과 벤치길이 변화에 따른 차이는 상대적으로 작은 편이었으나,2차원 수치해석에 의한 선행굴착을 고려하지 않은 경우와 강도응력비 비교를 통해 선행굴착이 분기 후 구간의 굴착 안정성에 영향을 미칠 정도로 큰 응력의 변화를 유발함을 확인하였다.

Abstract

The divergence section of a double-deck tunnel can be divided into a ‘wideningpre-divergence section’, a large cross-section with a cap shape and a ‘post-divergencesection’ where the separation between the main and the branch tunnel is made. Sincethe cross-section of the widening pre-divergence section is considerably larger thanthat of the post-divergence section, the influence of excavation due to the differentsizes and shapes in the cross-section should be considered in the examination of thetunnel stability. In this study, the effect of the preceding excavation, that is theexcavation of the widening pre-divergence section, on excavation stability of thepost-divergence section was examined by varying the excavation methods and benchlengths through 3D finite element analysis. The results showed that although theeffects of the excavation methods and the bench lengths are not significant on thevariation of principal stresses, the preceding excavation causes a relatively largevariation on the stresses which may have an impact on the stability of thepost-divergence section from the comparison of Stress-Strength Ratio (SSR) betweenthe cases with and without the consideration of the preceding excavation effect by 2Dfinite element analysis.

초록

단면이 작게 만들어진 노후화된 터널은 만성적인 교통정체를 유발한다. 이는 터널의 확폭을 통하여 해결할 수 있다. 일반적으로 터널을 확폭할 경우, 기계식 또는 발파식 굴착방법을 통하여 기존터널의 외곽부를 굴착하게 된다. 이러한 굴착은주변 지반뿐만 아니라 기존터널에도 영향을 미치게 된다. Pre-cutting 공법의 적용은 이러한 문제를 효과적으로 해결할수 있는 방법이 될 수 있다. 따라서 Pre-cutting을 적용하여 확폭을 수행할 경우, 이에 따른 영향분석은 필수적으로 수행되어야 한다. 본 연구에서는 터널 확폭에서 Pre-cutting을 적용할 경우, 이에 따른 영향을 분석하기 위하여 6가지의 지반등급에서 수치해석을 수행하였다. 해석에서는 확대차로와 Pre-cutting의 굴착길이를 변수로 하여 수행하였으며, 기존터널과 확폭터널의 천단침하에 주목하여 분석하였다. 그 결과, 확폭터널의 천단침하는 확폭이 완료가 되면, Pre-cutting의굴착 길이와 상관 없이 동일한 값으로 수렴하는 것을 확인하였다. 기존터널의 경우, 굴진면의 전방 5 m 내에서 융기가 발생하였으며, Pre-cutting의 굴착 길이가 짧을수록 융기 발생 예방에 효과적인 것으로 나타났다.

Abstract

Aging tunnels with small cross-sections can cause chronic traffic jams. This problemcan be solved by widening the tunnel. In general, when the tunnel is expanded, theouter portion of the existing tunnel is excavated through a mechanical or blastingmethod. Such excavation affects not only the surrounding ground but also the existingtunnel. The application of the pre-cutting method can be a solution to these problemseffectively. Therefore, if the widening of tunnel is performed by applying pre-cuttingmethod, analysis of the impact of this method must be performed. In this study, in orderto analyze the effect of applying pre-cutting in tunnel widening, numerical analysis isperformed at six ground grades, from grade I to weathered rock. The analysis isperformed with the expanding lane and the excavation length of pre-cutting asvariables. In addition, the analysis is focused on the displacement of crown of theexisting tunnel and the enlarged tunnel. As a result, the crown displacement of theenlarged tunnel is confirmed to converge at the same value regardless of theexcavation length of the pre-cutting when the tunnel widening is completed. In thecase of existing tunnels, uplift of crown occurs within 5 m of the front of the tunnelsurface, and the shorter the excavation length of pre-cutting is found to be effective inpreventing the occurrence of uplift.

초록

Abstract

This study focused on shielding through inflatable structure in the event of suddenwater inflow into the submerged floating tunnels. Currently, there is a lack of measuresto deal with unexpected water in tunnels in Korea. Although water treatment facilitiessuch as waterproofing and floodgates in tunnels are installed, there are limitations tothe sudden inflow of large amounts of seawater or underground water. Also, floodgatescannot respond quickly to sudden damage due to slow blocking time. Accordingly, astudy was conducted on the shielding rate and axial movement distance for inflatablestructure. The results of the reduced model experiment confirmed that the number ofinflatable structure and internal pneumatic pressure influence on the shielding rate. Asthe number of inflatable structure increased from one to two, the shielding rateincreased by about 35 up to 40 percent. It was also confirmed that the shielding rateincreased by about 4 percent as the internal pneumatic pressure increased from 0.2 barto 0.3 bar. If we verify and further develop the results identified in this study througha real-size experiment, it will be able to be used as an effective waterproof measure forsudden water inflow into the undersea tunnels or underwater tunnels.