順向坡地區的山崩機制調查與活動性探討－以嘉義太和地區為例

The Study of DIP Slope Landslide Mechanisms and Activities in Tai-Ho Village, Chia-Yi County

林錫宏(Hsi-Hung Lin) ； 林銘郎(Ming-Lang Lin) ； 紀宗吉(Chung-Chi Chi) ； 費立沅(Li-Yuan Fei)

《工程環境會刊》 33期 (2014/07) Pp. 1-16

https://doi.org/10.6562/JEE.2014.33.1

摘要

順向坡是臺灣山區常見的地形構造，在極端天氣的劇變環境下，會在豪雨或地震中，發生大規模平面型岩體滑動災害。以嘉義縣梅山鄉太和地區為例，位於背斜東翼及背斜軸向西南傾沒處的坡面，可能均屬於順向坡。其中油車寮地滑為大規模平面型岩體滑動，滑動面可能為既存的層間剪裂帶。從平面型岩體滑動的邊坡穩定分析及參數敏感性研究發現，滑動面的摩擦角對於邊坡穩定的安全係數，具有最大的影響性，其次是張裂縫及滑動面的蓄水比。在構造作用中，層間剪裂帶容易在褶皺翼部發展，尤其在厚層砂岩的頂部或底部。數值模擬中也發現，即使在順向坡尚未砍腳的狀態，層間剪裂帶的弱化及其上覆岩體的風化，對平面型岩體滑動的發展，亦具有不利的關鍵影響。考量漸進式邊坡破壞模式，對於危險且具有山崩活動性徵兆的順向坡，宜有詳細的山崩機制調查及長期自動觀測，以進行防災策略的規劃。

關鍵字

順向坡 ； 山崩機制 ； 邊坡深層變形 ； 平面型岩體滑動 ； 層間剪裂帶 ； 漸進式邊坡破壞

並列摘要

The translational rockslide in dip slope was triggered by heavy rainfall during typhoon Morakot in 2009 near Tai-Ho village, Chia-Yi County. After detailed investigation, the rockslide resulted from translational sliding along bedding planes at top of a thick sandstone, and may be an old deep-seated slope deformation. The sliding zone at top of the thick sandstone also resembles interlayer shears inside the rockslide or nearly stable slope. Sensitive analysis indicates that the friction angle of interlayer shears is the most sensitive factor which influences the safety factor of slope stability. If interlayer shears originated from flexural folding were weakened by old events of deep-seated slope deformation and weathering, lower friction angle as residual strength is possible and subsequently become the potential sliding surface for translational rockslide, even in the dip slope without daylight. Therefore the existence and shear strength of interlayer shears should be carefully examined for slope stability.

並列關鍵字

Dip Slope ； Landslide Mechanisms ； Deep-Seated Slope Deformation ； Translational Rockslide ； Interlayer Shears ； Progressive Failure