英文篇名
Geological Characteristics and Associated Influences on Highway Maintenance Engineering - Revealed by Experience Learned from East Section of Central - Cross Island Highway
作者
劉世桐、李佳翰、王泰典
關鍵字
中橫公路、養護、工程地質特性、國際造糙度指標(IRI)
摘要
本文以非傳統養護工程經驗-包括歷年災修經費、國際糙度指標IRI值以及致災雨量等之統計分析,重新檢視公路養護路段的工程地質特性,並探討其對公路養護作業的影響。中橫公路致災臨界雨量偏低,顯示自然邊坡抗災能力不佳。致災類型受到公路所處邊坡的區位以及該處工程地質特性高度影響,可歸納為下邊坡岩體滑動與岩屑崩滑引致的路基災害、公路兩側上、下邊坡岩體滑動與岩屑崩滑引致的崩塌問題以及公路上邊坡穩定性不佳,引致落石造成的上邊坡災害;而高山氣候凍融作用、葉理與其形成的順向坡、發達的褶皺與片理、片岩與大理岩界面差異侵蝕形成的弱帶以及立霧溪與其上游支流的向源侵蝕,則為公路路基與上邊坡災害主要的工程地質因素。IRI值不僅反映路面平坦度,亦與公路下邊坡的穩定具相關性,其於反映路基災害現象與致災臨界雨量等防救災實務的應用值得進一步探討。
英文摘要
This study adopts a non-conventional maintenance approach, including statistical analysis for correlation between historical repairing costs, international roughness index (IRI) along a road and the critical precipitation that causes instability for highway neighboring slopes, to examine the geotechnical characteristics along the eastern section of the central-cross island highway and associated influences on its maintenance tasks. The critical precipitation is relatively low, indicating that the highway has poor resistance to nature disaster. Hazard types for the highway are mainly affected by its relative location to a slope and geotechnical characteristics, and can be classified into three major types: 1) Roadbed disaster caused by rock sliding or debris fall with a creak-side slope neighboring to the highway, 2) traffic blocked caused by rock sliding or debris fall with slopes next to the highway, and 3) rock fall from a hill-side slope neighboring to the highway. Geotechnical factors accounting for these highway hazards include the freezing and thawing effect in high elevation mountain area, foliation and associated dip slopes, well-developed folding and schistosity, differential erosion in boundary of schist and marble stratum and associated weak zone, and regressive erosion on upstream of Liwu River and its branches. Additionally, the IRI can estimate smoothness along the highway, and also has relations with creak-side slope instability. Application of IRI for disaster presentation and mitigation, such as describing roadbed disaster and its relation to critical precipitation for various sections of the highway, are worth further study.