隧道混凝土襯砌火害後剝落之縮小模型實驗與模擬分析

當隧道發生火災後，混凝土襯砌有可能因暴露於高溫之火場環境，而產生剝落之現象，此將造成隧道內頂部之混凝土或固定之機電設備有墜落之可能，進而影響用路人之避難安全及救援行動之進行。由國內外之文獻得知混凝土含水量為影響剝落之主要因素，因此本研究針對隧道混凝土襯砌建立縮小尺寸之模型進行火害實驗，以實驗所量測之加熱面升溫曲線套入數值模型，分兩階段進行熱分析與熱應力分析，第一階段之熱分析與實驗所量測之內部升溫曲線做對照及修正，其實驗值與模擬值之溫度差異百分比在6％以內，也確定數值模型能有效計算出混凝土襯砌在不同含水量影響下的溫度分佈狀況，第二階段熱應力分析的結果與實驗對照之後，發現當混凝土襯砌含水量從2％增加到6.7％時，表面最大熱應力值會增加83％左右，而含水量增加到4.5％時就會產生裂縫破壞。此外也嘗試分別改變火害最高溫度、土壤含水量、改變襯砌之骨材含量、水灰比，模擬之結果顯示，當混凝土襯砌受火害時，熱應力與溫度分佈受外在環境的影響較大，而本身配比之改變影響較不明顯。

關鍵字

熱應力；襯砌；含水量；剝落

並列摘要

Small-scale specimens were cast to study the spalling of concrete linings of tunnels. The specimens, 34 cm in diameter and 35 cm in length, were heated to 800oC in 9 minutes and kept for 30 minutes before the electrical oven was turned off. Finite element models were analyzed based on the temperature history recorded at various locations of the specimens. Transient thermal analysis was performed and corresponding results were compared with experimental temperature history. Modifications were then made to the models such that the temperatures at various locations were in agreement with experimental results for three levels of moisture content in the concrete linings. Subsquent analysis found that the maximum thermal stress increased 83% as the moisture content was raised from 2% to 6.7%. The analysis also found that the distributions of thermal stress were most likely to be affected by the maximum exposure temperature and the moisture content in the earth in direct contact with the concrete lining.

並列關鍵字

thermal stress ； lining ； moisture content ； spalling

參考文獻

【11】危時秀，「普通混凝土熱傳導性質之研究」，碩士論文，中原大學土木工程學系，中壢，2003。

【14】黃彰斌、林誠興、徐瑞祥，「鋼筋混凝土樑受火害時之溫度分佈與殘餘強度分析」，學術期刊，二十一卷，第二期，第175-188頁，2006。

【30】林世泰，「中正國際機場混凝土鋪面的溫度效應之研究」，碩士論文，國立台灣大學土木工程學研究所，台北，2003。

【2】 K.D.Hertz, “Limits of Spalling of Fire-Exposed Concrete”, Fire Safety Journal, Vol. 38,No. 2, pp.103-116, 2003﹒

【3】Alan Beard and Richard Carvel, “The Hand Book of Tunnel Fire Safety” [M], Thomas Telford, 2005﹒

國際替代計量

隧道混凝土襯砌火害後剝落之縮小模型實驗與模擬分析

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