林肯大郡地層滑動災變原因之探討

The Causality of the Catastrophic Rock Slide in Lincoln Residence, Taipei County

紀宗吉(Chung-Chi Chi) ； 林朝宗(Chao-Chung Lin) ； 劉桓吉(Huang-Chi Liu)

《地工技術》 68期 (1998/08) Pp. 67-74

https://doi.org/10.30140/SG.199808.0004

摘要

86年8月18日上午八時許，適逢溫妮颱風侵襲，並挾帶非常豐沛的雨量，位在汐止鎮林肯大郡社區後方的邊坡突然滑動，瞬時之間，造成房屋80戶全毀、20戶半毀，居民死傷近百人的重大慘劇。本次地層滑動的方式是沿著頁岩間的頁理面滑動，根據現場滑動的特徵，又可以分為二個滑動塊體，二個滑動塊體均位在同一底滑動面上，滑動的方向為南偏東10度。滑動區的地質是屬中新世石底層近底部的岩段，由頁岩、砂岩及砂、頁岩薄葉互層所構成。從滑動的材料以及滑動面的特徵與坡型的關係，此次發生的是屬於順向坡平面型滑動；而造成如此巨大的地質災變，除了對地質條件未能重視外，工程規劃設計的諸多缺失實為主因，其原因大致可歸納如下：1.滑動區屬於標準的順向坡地形，過去已有類似的滑動情形發生；2.邊坡的坡腳遭挖除，岩體的滑動面出露，在支撐力不足下，造成地層的滑動；3.擋土牆、地錨保護結構設計，深度與密度不足，逐漸失去功能；4.地下水無法有效排出，造成地下水壓升高、頁岩軟化，頁岩的抗剪強度降低；5.建築物配置與擋土牆安全距離不足；6.建築物配置方向與地層走向相近，破壞最大。

關鍵字

林肯大郡 ； 順向坡 ； 山崩災害

並列摘要

The intense rainfall associated with Typhoon Winny, passing through northern Taiwan in August 18, 1997, triggered a fatal rock slide disaster in Lincoln residence, Taipei County. The slope failure destroyed and damaged 100 houses located in downslope area. 28 lives were killed and 50 injured by the collapsed buildings. The failed slope is comprised of the Miocene Shiti Formation, which is mainly composed of alternation of the sandstone and shale with the bedding plane dipping 30 degree downslope. The planar failure occurred along bedding plane and a huge slab of rock with 150m (Length) X 58m (Width) X 10m (Thickness) in size moved downslope rapidly. The moved slab was also separated into two halves by an extensional joint trending perpendicular to the strike of bedding plane during the movement. The main causalities of the catastrophe can be mainly attributed to the improper design of the housing project. First of all, the designers ignored the geological conditions of the unstable dip-slope consisting of bedded sedimentary rocks with weak bedding planes. The supporting material had been unwisely removed from the toe of the slope during construction at the base of the slope. After the intense rainfall, the high water pressure accumulated behind the retaining wall and decreased the friction of the bedding plane. The strength of retaining wall and anchors been set on the slope are insufficient to retain the unstable block from downslope movement.

並列關鍵字

Lincoln Residence ； Dip Slope ； Landslide Disaster