侯硐地區土石流材料—在不飽和狀態下剪力強度之研究

陳奕豪(Yi-Hau Chen)

指導教授 ： 陳榮河

國立臺灣大學/工學院/土木工程學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01591

摘要

摘要
降雨入滲會改變邊坡之不飽和特性，造成坡體之破壞；同時，由於不飽和土壤相關理論在近二十年來逐漸發展成熟，已可廣泛應用在現地不飽和邊坡穩定性之評估。因此，本研究針對瑞芳侯硐地區之土石流源頭處進行研究，探討邊坡之不飽和特性與降雨入滲行為，以分析民國89年象神颱風造成候硐地區土石流災害起動原因，以期進而對土石流發生特性有所了解。
本研究主要分為室內試驗與程式分析兩部分，室內試驗乃針對侯硐地區大粗坑之土石材料，進行飽和三軸試驗、不飽和三軸試驗與土壤水分特性試驗，以瞭解其土石材料特性；再將試驗結果與前人研究(各土石流源頭處)進行討論與比較。邊波穩定分析則針對瑞芳侯硐地區，利用STABL程式，對降雨入滲進行模擬，以了解現地之災變過程等。
試驗結果顯示，大粗坑土樣之剪力強度其參數，其有效凝聚力c’=0，而有效摩擦角ψ’=43.2°，而大粗坑土樣在不飽合狀態下，其剪力強度提升十分有限，其不飽和剪力強度參數ψb介於1.4°~3.5°，與基質吸力呈非線性關係，主要原因是應為其細粒料含量很少所致，另外大粗坑土樣之保水能力不佳，故在低基質吸力時，其水分已大量流失，所以土體在高低基質吸力下，土壤之含水量變化不大。
而在邊波穩定分析結果方面，以STABL分析昇升幅坑邊坡之穩定性，發現到昇福坑邊坡平時安全係數就偏低（FS＝1.28），且降雨對邊坡之安全因數之影響十分顯著，當降雨入滲達11.5m時，邊坡之安全因數就很接近1，且可能滑動面都集中在邊坡上端，這與實際之破壞情形大致符合。

關鍵字

邊坡穩定 ； 降雨入滲 ； 土石流材料 ； 不飽和土壤

並列摘要

Abstract
The theory of unsaturated soil has developed completely in the past twenty years, and it can extensively apply to evaluate the stability of unsaturated slope. Furthermore, the unsaturated soil properties are very much affected by the infiltration of rainwater. The study area in the Houtong area located Rueifang in Taipei County. The contents of this research include two parts: laboratory tests and numerical analyses. The tests conducted include isotropically consolidated undrained triaxial (CIU) test, soil-water characteristic curve test, consolidated drained triaxial (CD) test on unsaturated soil sample, etc. The analyses simulate the process of infiltration utilizing STABL computer programs.
As a result, the effective cohesion (c’) and the effective angle of friction are determined as 0 and 43.2°, respectively, according to the tests of soil samples from Datsu Greek. The intensity of stress of the soil increases slightly under the unsaturation condition. The unsaturated soil parameter (fb) ranges from 1.4° to 3.5° and has the nonlinear relationship with the suction of the substrate because of the few content of the fine sandy. In addition, the ability of water maintain of the soil sample from Datsu Greek is poor. Most water would flow out in the condition of low suction of the substrate. Therefore, the water content in the soil varies slightly at low suction of the substrate.
Moreover, the stabilization of the side slope is analyzed by STABL. The safety coefficient of the side slope is low with the value of Fs =1.28. Furthermore, the effect of the rainfall is significant to the safety factor of the side slope. The safety factor of the side slope is close to one while the penetration of the rainfall reaches 11.5 m. The slip level is mainly focus to the top of the side slope, which is consistent to the real situation of destruction in situ.

並列關鍵字

stability of slope ； initiation zone of debris-flow ； infiltration ； properties of unsaturated soil

參考文獻

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