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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

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.
Appears in Collections:土木工程學系所

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