高速公路礫石隧道設計之探討

STUDY ON DESIGN OF HIGHWAY GRAVEL TUNNEL

礫石隧道之設計施工與岩石隧道有著明顯的不同,如在岩體分類方面無法使用岩石隧道常用的南非CSIR-RMR及挪威Barton-Q值之定量評估方法。另其工址調查也常因粒徑及採樣不易,無法進行室内試驗而影響力學參数的評估。近年來雖有部分礫石隧道個案完成,然而礫石隧道所佔比例仍屬稀少,因此礫石隧道之施工經驗仍較缺乏,對於高速公路等级而言更是首例。由於礫石隧道地質之特殊,致隧道設計之前應對台灣礫石地層之成因及類型等有基本認識,充分瞭解礫石層之地質特性與力學性質,才能進一步探討礫石隧道之相關課題。首先針對上述因素加以探討,然後以一礫石隧道設計實例來說明設計之實際考量及過程,最後進行隧道之支撐設計及數值模擬比較,俾供後續類似地層設計之參考。

The design and construction of gravel tunnel and rock tunnel are different. Rock classifications, such as CSIR-RMR method and Barton-Q system, are not suitable for the gravel tunnel. Because of the difficulties in sampling in site investigation and determining grain size, the laboratory tests are not so convenient to carry out for obtaining the ground parameters. Although some gravel tunnels have been finished in the recent year, the available experience is still inadequate. In the first case of highway gravel tunnel in Taiwan, the geological and mechanical characteristics are fully studied prior to tunnel design. The design methodology is introduced, in which the characteristics mentioned above are considered. The numerical analysis on the support system is then carried out.