集集地震引致臺灣中部山區邊坡臨界滑移量之分析

高贈智(Tseng-Chih Kao)

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(2004年)

https://doi.org/10.6342/NTU.2004.00455

摘要

台灣平地面積有限，山坡地的開發與利用相當頻繁，且台灣恰位於環太平洋地震帶上，故對於邊坡受震穩定性的分析便成為相當重要的一門課題。921集集地震的發生，使得台灣中部山區的坡地發生了大規模的破壞，影響了交通、經濟並危害了居民的生命安全，所造成的直接或間接的損失相當慘重，因此有必要對邊坡受震之分析做更進一步的研究。在前人分析邊坡受震的各種方法中，滑動塊體法簡便又可適當反應出邊坡受震行為，且參數取得容易又分析快速，可適用於大區域邊坡受震穩定性的評估。

本研究主要針對均質簡單邊坡，採用黃紀禎(2003)推導之對數螺線破壞面滑動塊體法，以此分析模式求取邊坡受震後的坡趾位移量及破壞面位置，並探討此法的適用範圍。由衛星影像及航空照片判釋崩坍資料，與現地調查崩坍資料中，篩選出適當崩坍案例，並配合地理資訊系統軟體ArcView空間分析之弁遄A求得崩坍地之坡度、坡向及土壤力學參數等，再加上集集地震的地震加速度紀錄，以對數螺線滑動塊體法進行分析。而使用滑動塊體法最主要的目的，乃是計算邊坡於地震力作用下的位移量，由此位移量判斷邊坡是否穩定。

本研究由篩選出的現地崩坍案例計算邊坡破壞的位移量，發現除了少數案例為5∼10公分外，其餘均超過10公分甚多，因此本研究建議導致邊坡受震崩毀的臨界位移量為10公分。另外由分析結果得知，對數螺線滑動塊體法的坡度適用範圍為20度∼45度，且坡度為影響邊坡降伏加速度的主要因素。

關鍵字

對數螺線破壞面 ； 集集地震 ； 滑動塊體法 ； 臨界位移量

並列摘要

Taiwan locates in the circum-Pacific zone with frequent earthquake activities, incessant cultivation and relentless exploration of the mountain areas, thus the analysis of the seismic slope stability becomes a significant issue. The Chi-Chi Earthquake in 1999 caused catastrophic damages to the slopes of the mountainous areas in central Taiwan, which threatened residents’ lives and caused adverse effects on traffic and economy. The direct and indirect losses associated with this earthquake are huge. Therefore, advanced research in analyzing slope under seismic loading is required. Among the various methods used to analyze the seismic slope stability, sliding block analysis is a simple and convenient way that not only describes the behaviors of seismic slopes but also can be used to evaluate seismic slope stability in large regions.

In this paper, simple-slopes with uniform soil properties and log-spiral failure surface method (Huang, 2003) are used to locate the failure surface and obtain the toe displacement. In addition, the suitable conditions which this method is applicable will be defined. In order to identity the proper land slide cases, satellite pictures, aerial photos, and reports from site reconnaissance will be used. Also, GIS software ‘ArcView’ will be used to extract data such as the failure slope angle, slope aspect and soil properties, etc. With the Chi-Chi earthquake acceleration record, log-spiral failure method can be used to calculate the slope displacement under earthquake loading and stability of slope can be evaluated accordingly.

The results from this research indicate that the critical displacements of most landslides are more than 10 centimeter while only a few cases are with 5 to 10 centimeter displacement. Therefore, it is suggested that 10 centimeters is the critical displacement where the failure of slope initiates. In addition, from the analysis results, the proper slope angle for using log-spiral failure surfaces method is 20 to 45 degree. In conclusion , slope angle is considered as the most important factor of the yield acceleration of slopes.

並列關鍵字

sliding block analysis ； log-spiral failure surfaces ； Chi-Chi Earthquake ； critical displacement

參考文獻

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