台北貓空纜車T16-墩柱邊坡（T16-邊坡）複合型整治工程之效益評估

Evaluating the Efficiency of Stability Remediation Measures for the T16-Tower Pier Slope of the Taipei Maokong Tramway

10.29417/JCSWC.201809_49(4).0002

林德貴(Der-Guey Lin)；張國欽(Kuo-Ching Chang)；鄒瑞卿(Jui-Ching Chou)

有限元素 ； 強度折減法(SRM) ； T16-邊坡 ； 複合型穩定工作 ； 降雨誘發入滲 ； 穩定性分析 ； 相對安全係數(RFS) ； Finite element technique ； strength reduction method ； compound stabilization work ； rainfall-induced seepage ； stability analyses ； Relative Factor of Safety

中華水土保持學報

49卷4期（2018 / 12 / 01）

214 - 232

繁體中文

本研究採用2D有限元素強度折減法(SRM)，執行一系列降雨入滲和邊坡穩定性分析，檢核台北市貓空纜車T16-墩柱下方邊坡（稱T16-邊坡）複合型整治工程之邊坡穩定效益。T16-邊坡複合型整治工程從上段、中上段、中段和下段邊坡，分別由四種工法組成。藉由比對2008年薔蜜(Jang-Mi)颱風期間現場觀測之T16-邊坡崩塌機制和發生時間，驗證數值分析模型和材料參數之有效性。數值分析結果顯示，T16-邊坡於2008年發生崩塌後，邊坡整治前、後之潛在滑動面皆發展於中上段邊坡（最關鍵區段邊坡），該處邊坡採用RC格梁地錨工法進行整治。在50年重現期距48小時設計降雨條件下，整治前、後最小安全係數分別為1.004（FS(t)_(整治前)）和1.191（FS(t)_(整治後)），顯示整治工程可避免中上段邊坡在暴雨期間之安全係數趨近於臨界狀態(FS=1.0)。本研究採用相對安全係數RFS（=FS(t)_(整治後)/FS(t)_(整治前)）評估整治工程對邊坡穩定性之貢獻度。在未降雨時，整治工程對邊坡穩定效果最好，RFS最高值達1.279，在50年重現期距48小時設計降雨條件下，當降雨延時t=30hrs時，RFS則下降到最小值1.145，顯示長延時劇烈降雨後，因雨水入滲影響，降低整治工程的穩定效應。

In this study, a series of rainfall-induced seepage and slope stability analyses was performed using the strength reduction method of two-dimensional finite element technique to inspect the efficiency of remediation measures for the down slope of the T16-tower pier (or T16-Slope), which is located on the hillside of Taipei City Maokong tramway. The compound stabilization work of the T16-Slope comprises four types of engineering methods, namely up-slope, up-middle-slope, middle-slope, and down-slope engineering methods. The numerical model and input parameters were calibrated by inspecting the coincidence between numerical results and field observations for the triggering mechanism and occurrence time of landslide in T16-Slope during Typhoon Jangmi in 2008. After the aforementioned landslide in 2008, the potential sliding surfaces of the T16-Slope with and without remediation measures were both developed at the up-middle-slope, where a RC-grid-beam (RC-grillage) and anchorage had been constructed for remediation. Under 48-hour rainfall over a 50-year return period, the minimum time-dependent factors of safety FS(t) with and without remediation measures were FS_(with)(t)=1.191 and FS_(without)(t)=1.004 respectively. The remediation measures prevented the up-middle-slope from reaching a critical state (FS = 1.0) during torrential rainfall. In this study, the relative factor of safety (RFS; RFS =FS(t)_(with)/FS(t)_(without)) was used to evaluate the efficiency of the remediation measures to protect slope stability. The RFS was highest (RFS=1.279) under the initial dry condition and lowest (RFS=1.145) during rainfall duration t=30 hours under design rainfall. The RFS values indicated that the stabilization effects of the remediation measures were significantly lower after prolonged heavy rainfall because of severe rainwater infiltration.

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