초록

Abstract

The behaviors of the ground in crossed zone and the existing upper tunnel in shallow cover due to the excavation of new lower tunnel Rectangularly crossed to that was studied. Model tests were performed in the large scale test pit, the size was 4.0 m (width) 3.8 m (height) 4.1 m (length)'. Test ground was constructed uniformly by sand in middle density. Results of the model tests show that earth pressure and settlement of the ground in crossed zone were redistributed due to the longitudinal arching effect by the excavation of lower tunnel. Upper tunnel blocks stress flow due to the longitudinal arching effect by excavation of lower tunnel.

초록

양방향 터널 (대면통행 터널)에 있어 방향별로 동일한 차속을 기준으로 터널환기를 분석하는 방법은 터널내 교통환기력을 거의 동일시하는 문제점을 내포하므로, 실제 양방향 터널에서 발생하는 다양한 조건들을 반영할 수 없다. 따라서 본 연구에서는 국내 터널환기 계획시, 양방향 차속의 불균등성 영향 분석을 목표로 하였으며, 차등차속의 영향을 환기계획에 고려하기 위하여서는 ① ‘고속-지체’시의 경우, 높은 차속에서의 매연의 허용기준을 적용할 필요가 있으며, ② 교통량의 적절한 중방향비율의 선정 및 ③ 적절한 차등차속차이의 단계를 결정할 기준마련 등의 필요성이 제기된다. 그리고 본 연구에서는 국내 양방향 터널의 환기설계시, 동일차속과 차등차속을 적용한 경우의 환기설비 규모 차이를 비교 분석함을 목적으로 한다.

Abstract

In general, tunnel ventilation is analyzed with the assumption of equal vehicular speed for both directions in bidirectional traffic tunnels. This practice is likely to result in minimizing the piston effects and cannot take into consideration the effects of real situations, since in most cases, speeds of vehicles moving in opposite directions are not equal. Therefore, The ultimate goal of this study is to review the effects of unequal vehicular speeds on the planning of local bidirectional tunnel ventilation. To apply unequal vehicular speed for the bidirectional tunnel ventilation plan, the following requirements are necessary; ① Adoption of strict smoke concentration standards for free-flow & congested' traffic conditions, ② Selection of an appropriate ratio of heavy directional traffic volume, and ③ Selection of reasonable stepwised magnitude of speed difference. Based on the importance of research topic, this study aims at comparing the differences of the capacity of ventilation equipment for the cases with equal and unequal vehicular speeds in local bidirectional tunnels.

초록

본 연구에서는 장대 터널 화재시 연기의 거동 특성 파악과 수직갱에 의한 배연 능력을 검토하기 위하여 축소 모형실험을 실시하였다. Froude 상사를 기본으로 수직갱을 포함하는 터널을 1/50로 축소하여 20m의 모형 터널을 제작하였다.화재시 발생되는 연기의 배연실험을 수갱의 높이를 변화시키며 한 결과, 수직갱에 의한 배연은 화재 후방으로의 역기류 전달 시간을 지체시키는 효과를 보였으며, 수직갱의 높이가 증가할수록 온도도 감소하였고, 중앙 높이에서의 온도차이는 수직갱이 없을 경우보다 다소 감소하기는 하나 그 영향은 미비하였다. 수직갱을 지난 지점에서 화재가 발생하였을 경우 수직갱의 높이가 증가하면 수직갱으로의 배연에 의한 역기류 활성화로 CO농도의 전파속도가 증가되며, 단면의 온도도 증가한다. 즉, 수직갱을 지난 지점에서 화재가 발생할 경우 수직갱은 화재 발생으로 인한 연기의 배연에는 유리하나, 오히려 역기류를 증가시켜 화재 초기 승객들의 안전한 대피에는 불리한 상황을 초래한다.

Abstract

The objective of this study was to analyze the smoke movement and to investigate the effect of exhaust ventilation using by shafts for case of fire in long tunnels. Based on Froude modeling, the 1/50 scaled model tunnel (20 m long) was constructed by acrylic tubes and test were carried out systematically. The results of the shaft height test show that the effect on exhaust ventilation by a shaft delays the propagation time of backlayering, and the temperature decreases as the shaft height increases. If the fire occurs downstream of the shaft, the backlayering develops to get stronger by the shaft exhaust effect and then the propagation of CO and temperature increase along with propagation of CO. That is to say, in the case of fire downstream of the shaft, the shaft has the advantage of smoke exhaust effects, but it might result in a dangerous situation for the escaping passengers due to the more developed backlayering.

초록

터널의 경우 지보재의 파괴가 터널의 파괴를 유발할 수 있으므로 지보재의 파괴가 고려된 안전율을 산정하는 것이 중요하다. 기존의 연구에서는 지보재의 파괴를 고려한 터널의 안전율 산정에 있어서 보 (beam)요소로 모델링하여 지보재의 파괴를 지보재에 발생하는 휨 응력과 허용응력을 비교하여 파괴를 고려하였다. 본 연구에서는 2차원 해석이 수행되었으며, 지보재를 보 (탄성)요소와 연속체 (탄소성)요소로 나누어 모델링하였고, 암반등급, 측압계수, 숏크리트 두께, 록볼트의 영향, 굴착방법이 터널의 안전율에 미치는 영향을 분석하여 적정 지보재의 모델링 방법을 제시하였다.

Abstract

In a tunnel, failure of its supports can cause failure of the tunnel. Therefore it is important to estimate safety factor of the tunnel which the failure of its supports is taken into account. In previous studies, supports of tunnels were usually modelled as beam elements. The failure of the supports was decided by comparing the allowable stress and the calculated bending stresses inside the beam elements in estimating safety factor of the tunnel considering the failure of its supports. In this study, it is suggested how to model the supports properly. To this end, supports of a tunnel were modelled by both beam (elastic) elements and continuum (elasto-plastic) elements in two dimensional numerical analyses. Meanwhile, it was analyzed how rock mass class, coefficient of lateral pressure, shotcrete thickness, the existence of rock bolt, and excavation method had an effect on the safety factor of a tunnel.

초록

Abstract

In general the strength parameter of the ground will be changed by reinforcing the ground around tunnel. In this case, the concept of tunnel design, such as supporting system, excavation, lining and so on, should be modified based on the failure criteria of the ground changed by the reinforcement. This paper presents the variation mechanism of strength parameters and new failure criteria of the reinforced ground. In order to perform this research, theoretical and experimental works were carried out. It was clearly founded that the cohesion of strength parameters is only increased by reinforcement of ground, especially by rock bolting.

초록

Abstract

The influence of internal water pressure under the Probable Maximum Flood (PMF) on tunnel spillway is analysed using 3D FDM analysis. HEC-RAS program including 1-D hydrologic numerical model was also implemented to estimate the maximum pressure on the lining under the PMF, thereafter, determined rational internal water pressure. Tunnel spillway was designed as twin tunnel and excavation and supporting stages are fully considered. Analysis was classified into the 3 cases; pressure is applied only to the left tunnel, only to right tunnel, and to both tunnels. The maximum tensile stress and axial force in supporting materials induced by water flow were compared with the critical values to assess the stablilty of the tunnel and the locations of stress concentration parts were also examined.

초록

Abstract

Three approaches presently used for the design of underground structures in rock mass are quantitative rock mass classification system, classification systems based on the behavior of the rock mass during excavation and general qualitative procedures for the design process. In this study their characteristics and shortcomings are discussed, and Austrian guideline for tunnel design/ construction, that was proposed to solve the problems with these methods, are introduced and compared. For technically sound and economic tunnel construction, a flexible design and construction procedure is needed to cope with uncertain ground and boundary condition, and also actual ground condition should be predicted through feedback of geotechnical information obtained during construction.

초록

Abstract

Due to fast development of digital equipments, various information techniques have been applied to the tunneling and a decision aid system based on IT has also been used during excavation stage. A PDA based informative tunneling method is, therefore, studied in this paper and the decision aids for tunneling using digital face mapping data as well as geologic information in terms of digital data is developed. For this, wireless network, mobile computer, CDMA and digital camera have been combined to generate the digital map of the tunnel face and reinforcement or excavation pattern can be estimated based on digitalized geologic conditions. Future studies will be concentrated on the enhancement of the PDA S/W so that reinforcement method as well as the amount of reinforcements can also be stored in the same DB. Furthermore, field application of the S/W will be undertaken and a virtual reality technique will also be introduced to visualize all the tunneling work on the computer monitor.