國道三號師公格山順向坡崩塌之可靠度分析

Reliability Analysis of the Mt. Shih-gong-ge Landslide on Fwy.3

秦瑞宏(Rei-Hung Chin)

指導教授 ： 林美聆

國立臺灣大學/工學院/土木工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003831

摘要

台灣位於環太平洋火山地震帶上，地震頻繁，氣候上屬副熱帶季風氣候，每年之平均降雨量為世界平均降雨量三倍之多，此兩項因素更是促成山崩為台灣常見之天然災害，而對於山坡地之工程開發，順向坡坡腳開挖往往為工程上一項重大的議題。
由於2010年4月25日，國道三號3.1公里處發生了大規模的順向坡平面滑動，此次邊坡破壞事件發生時及邊坡破壞發生前數日並無任何降雨事件及地震，且該工程於災後調查時確認原設計之邊坡穩定分析結果，安全係數均滿足交通部規範所需之要求，仍發生了大規模的順向坡滑動，於邊坡穩定分析中，地層材料參數、地層剖面以及地下水位分布情況之資訊，是極為重要的，而分析結果可能受限於對該地區所掌握之邊坡穩定分析之資訊不夠正確，而導致不正確之邊坡穩定分析結果。
本研究中蒐集大寮層中之地層材料參數，利用高精度之數值地形模型，搭配設計階段之地質柱狀圖及孔內攝影所量測到之層面位態建立地層剖面圖，接著經由監測而得之地下水位及雨量資料，建立本案例之地下水位曲線，並將上述資訊輸入邊坡穩定分析軟體FLAC中進行分析，並找出邊坡之臨界剖面。
於1998年國道三號施工過程中有發生異常狀況，邊坡上地錨荷重計讀值異常上升之情形，故於本研究中將試著反算出因此工程而導致坡體之岩體強度下降幅度，並根據反算出之結果，利用一階二次矩法(FOSM)對國道三號3.1公里處之師公格山順向坡進行可靠度分析，評估破壞機率。

關鍵字

邊坡可靠度 ； 順向坡 ； FLAC ； 一階二次矩法 ； 國道三號3.1K

並列摘要

Taiwan is located in Circum-Pacific Seismic Belt, and has a subtropical climate. Therefore, Taiwan is frequently hit by Typhoon and earthquake. Taiwan’s mean annual rainfall is three times bigger than the world. Both earthquake and rainfall are the two main reasons caused landslide becomes one of the frequent natural disasters in Taiwan. For slopeland development, the daylighted cut slopes is an important issue.in engineering.
Due to the dip-slope failure at the 3.1k section of Freeway No.3, which occurred on April 25 2010. There were several days without rain fall or earthquakes before the landslide. This project’s overall stability had been checked during investigation. Its Factor of Safety is without problem according to the specifications of MOTC. However, the disaters still happened. In slope stability analysis, the rock parameters, rock strata profile and the groundwater level information is really important. The result of slope stability analysis may be wrong due to the information input into the model is not exactly right.
In this study, we collected the rock parameters in Miocene Taliao formation.Then used high-resolution DEMs, the geologic column made in design phase of Freeway No.3 and the attitude measured by borehole imaging to establish the strata profile.And try to used the relationship between rainfall and groundwater data to generate the groundwater table of the slope. Finally, put the information as mentioned above into the numerical modeling software(FLAC) to find the critical profile of Mt.Shih-gon-ge.
During the construction of Freeway No.3, the measured loads of ground anchor load cell was abnormally raised. In this study, we used back analysis try to simulate the rock strength decreased due to the construction of Freeway No.3. Then we used the result of back analysis and use First order second moment method (FOSM) to calculate the failure probability of Mt.Shih-gon-ge.

並列關鍵字

Slope reliability ； Dip-slope ； FLAC ； 3.1k section of Freeway No.3 ； First order second moment method(FOSM)

參考文獻

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