Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/14940
標題: 膠結不良岩層力學行為之研究
A study of the mechanical behavior on poorly cemented rock
作者: 許慶祥
Hsu, Ching-Hsiang
關鍵字: soft rock;軟弱岩石;weaken;scale effect;in-situ direct shear test;弱化;尺度效應;現地直接剪力試驗
出版社: 土木工程學系
摘要: 
台灣西部麓山帶地質區之上新世晚期至更新世之地層在地質年代上沉積時間短暫,以致壓密不足,膠結疏鬆,成岩作用未達緻密狀態,形成膠結不良之岩層,此類岩層在浸水後,易弱化及消散崩解,其對水庫蓄水後邊坡穩定之影響頗大,文献中對於此類岩層特性敘述雖多,惟實際於現場進行大型之剪力試驗尚缺,使得相關強度參數之研究仍不完整。本研究旨在回顧過去對於此類岩石之研究文献及探討既有之相關調查、鑽探及試驗成果,並於寶山第二水庫左壩墩山脊平台位置進行大型現場直接剪力試驗,並取樣於試驗室進行岩石消散耐久性試驗、室內直接剪力試驗及飽和三軸不排水剪力試驗,藉試驗之成果加以比較,研究此類岩石在浸水與不浸水之受剪行為及力學性質,並探討岩體的尺度效應之影響,以提供寶山第二水庫邊坡穩定強度參數之分析及設計參考,並期能提供台灣西部麓山帶膠結不良岩層強度參數分析之參考。
本研究顯示,本區之地層屬於更新世之楊梅層,出露之岩性均屬非常低耐久性且膠結不良之軟岩,經浸水及擾動後已無凝聚力,其中又以泥岩浸水強度弱化較為嚴重,整體而言,軟岩浸水後強度約折減20%左右,故未來水庫蓄水時應留意泥岩邊坡或具砂泥岩互層面之邊坡穩定性。比較試驗結果,軟岩之尺度效應與傳統之認知有所不同(岩體強度隨著尺寸之增大而降低),研究結果顯示本區軟岩岩體剪力強度與試體尺寸並無明顯關聯,若以不擾動試體並輔以精密控制之室內三軸試驗可得到經濟且可靠之軟岩剪力強度參數。

The geology of the western mountain region of Taiwan, which is between Pliocene and Pleistocene, is deposited in short period. As a result of incomplete diagenesis sedimentary rock is ill cementation. This kind of the rock is easier to be weakening and collapse when flooded. It has a huge impact on stability of the slope when the reservoir retains water. There are many documents researching about the rock, but we didn't have in-situ direct shear test yet. Therefore there are still insufficient papers about strength parameters. Now we not only do in-situ direct shear test on the ridge platform in the left side of the dam of the Bao-shan Ⅱ reservoir but also sample to do slaking test, direct shear test, and triaxial shear test with saturation and undrained condition. Then we compare with the results and find out the characters of mechanics whether soft rock is flooded. Analyze the influence caused by scale effect in soft rock to design stability of the slope of the Bao-shan Ⅱ reservoir. The results also provide strength parameters for the ill-cementation rock in the western mountain region of Taiwan.
The results show the stratums of ridge platform in the left side of the Bao-shan Ⅱreservoir belong to Yang-Mei deposit of Pleistocene. All the outcrops are soft rock with low durability and ill cementation. When soft rock is flooded or disturbed, the cohesion is almost none. Especially, the shear strenght of mudstone drops off a lot when flooded. Averagely, the soft rock loses 20% off the shear strength when flooded. Compare with direct shear test in laboratory and in situ, we find out that scale effect in soft rock is different from the tendency that we know in rock mass. The strength of soft rock is not so apparent as the sample size. Triaxial test that is under precision control can gain representative and economical shear strength parameters.
URI: http://hdl.handle.net/11455/14940
Appears in Collections:土木工程學系所

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