砾岩地层滨海公路隧道选线与规划案例探讨

Study on Rroute Selection and Planning of Tunnel Underwent Conglomerat in Coastal Highway

台湾东部滨海公路改善工程某隧道通过八里湾层与蕃薯寮层,岩性主要为砾岩、砂岩、泥岩及其互层,选线过程考虑地质特性、地形限制与施工维持等因素,并将生态保育、景观美质与工程技术等纳入规划与设计中。惟施工过程遭遇地形变动剧烈、洞口边坡与隧道围岩遇水弱化、依时变形显著等不利因素,历经数度修正设计得以突破。以此案例为背景,提出砾岩的工程特性以及隧道选线与规划相关建议。

The case tunnel presented in the paper, located in coastal highway at eastern Taiwan, passes through Paliwan Formation and Fanshuliao Formation. The rocks are mainly composed of conglomerate, sandstone, mudstone and their interlacing. During route selection and planning stages, the geological properties, terrain characters and traffic maintenance have been considered, and the ecological and environmental protection, landscape and the construction technology are thoroughly examined. However, the rocks suffer severe weakening as saturated, meanwhile the time-dependent deformation are also distinct. These unfavorable engineering characteristics resulted in the variation of landforms happened in evidence, and jeopardized tunnel construction many times. This paper reviews the route selection and planning tasks of the tunnel, and lessons learned from the project are commented accordingly.