順向坡之破壞與穩定

A Study on the Failure and Stability of Dip Slopes

洪如江(Ju-Jiang Hung)

《地工技術》 94期 (2002/12) Pp. 5-18

https://doi.org/10.30140/SG.200212.0001

摘要

在台灣，大多數大規模與中等規模之坍方災難，由順向坡滑動所造成。著名之例包括草嶺大崩山、九份二山大崩山、汐止林肯大郡坍方、國道中山高速路八堵交流道坍方、國道中山高速公路汐止收費站附近北坡坍方、台北市松山之虎山坍方、等等；每一次順向坡滑動都造成數十人之死亡或交通中斷。義大利Vajont水庫邊坡大坍方，Longarone村村民遇難者1909人，為世界上最慘的一次順向坡破壞之災。台灣的中、大規模順向坡滑動，多發生於麓山帶的砂、頁岩地層中。脆裂之砂岩下接頁岩或泥岩層，常在持續豪雨或強烈地震的侵襲下滑動。潛在滑動面在坡面或坡趾「露空」，常造成順向坡滑動；但潛在滑動面之「露空」，並非順向坡滑動的必須條件，更非順向坡滑動的充分條件。許多大規模順向坡滑動，其潛在滑動面，常在滑動之前已經開裂或早已經過多次滑動，故大多數順向坡滑動之分析，只考慮剩餘剪力強度，而且常假設Cr=0。邊坡穩定分析，在確定影響穩定的主要變數之後，應辦理敏感度分析，以明白某一重要變數（例如水壓、摩擦角）的單位變化，會引起邊坡穩定安全係數的多大變化。本文以國道中山高速公路汐止收費站附近順向坡滑動為例，加以示範。

關鍵字

順向坡 ； 破壞 ； 穩定

並列摘要

Most medium- to large-scale landslide disasters in Taiwan are due to dip-slope failures in sandstone and shale formations in the foothill region of western and northern Taiwan. The Tsao-Ling landslide, the Juo-Feng-Err-Shan landslide, the the Lincoln Villa landslide, the Pa-Du landslide, the Shi-Tz landslide, and the Mt Tiger landslide, have been the most noted dip-slope failures in Taiwan. Each of the landslides caused loss of tenth of human lives or interruption of transportation. The great destruction and loss of 1909 human lives caused by the Vajont Slide on 9th October 1963, in Longarone of Italy, has been the most disastrous dip-slope failure in the world.Exposure (or daylighting) of the potential slip-plane is often but not always a necessary condition for the occurrence of dip-slope failures. A failure surface can be hybrid, which is originally made up of pre-existing natural weak plane and intact rock material before being sheared through.For many large-scale dip-slope failures, their potential slip-plane had opened up or slipped before failure. It is therefore that only residual shear strength is used for most dip-slope stability analysis, and that residual cohesion is taken to be zero.The Shi-Tz dip-slope failure has been reanalyzed to illustrate that the water pressure in the vertical open joint and on the potential slip-plane is very sensitive to the stability of a dip-slope.

並列關鍵字

dip-slope ； failure ； stability