| Summary: | 碩士 === 國立臺北科技大學 === 土木與防災研究所 === 94 === Most land formations in Taiwan are mountain regions. Transportation in the isl- and is inconvenient because of mountainside obstructions; therefore, the demolitions of such hillside obstructions are usually the prime target of a transportation road construction,and chiseling of the tunnel is the most direct access.
The cavity is starting point of a tunnel and the only access during construction. In most cases, the cavity of a tunnel could not be established at the most favorable terrain and geological condition because of the limitation of existing roadways. It usually has to be located at weathered sloping area or sedimentary bank where both the terrain and geological conditions are unfavorable of excavation. Therefore, the mutual relationship between a cavity and its adjacent slope is the most essential subject, which has challenged the wisdom and skills of engineers.
The placing of a tunnel cavity should be arranged in a way to minimize the excavation of a slope as much as possible. The geo-technical problem resulted from excessive excavation of a slope usually surpasses the tunnel construction itself. The concept of “protect a slope before excavating a tunnel” is the utmost provisional principle of tunnel cavity construction.
This thesis is processed by taking several case studies of previous documented slope collapses because of tunnel cavity construction. Next to that, the thesis also discusses the essential awareness of the inter-relative aspects between a tunnel and its sloping area on building a tunnel cavity. Moreover, successful examples of projects that had managed to escape from the disadvantageous effect to the adjacent slope are also been analysis and introduced. Meanwhile, a construction method – “Invert Cover Construction Method” is also introduced. Through computer mock-up analysis and actual site construction against the calculation result, the combination of grating slope protection and earth anchor with the invert cover can actually provide the protection and support to the stability of adjacent slope during. With the aforementioned method statement, it can provide precedent samples to other projects that have similar terrains and geological conditions. Furthermore, it is highly potential to extend this construction method for computer mock-up analysis as the reference to projects on worse terrain and geological conditions.
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