(사)한국터널지하공간학회
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- P-ISSN2233-8292
- E-ISSN2287-4747
- KCI
ISSN : 2233-8292
Vol.7 No.1
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.
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.
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.
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.
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.
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.
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.
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.