Study on Factors Affecting Strength and Deformation Modulus and Associated Weakening and Softening Phenomena of Clastic Rocks

• Main Authors: Ying-Jie Zeng, 曾瀅潔
• Other Authors: Huang Tsan-Hwei
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/22641333295990563562

碩士 === 國立臺灣大學 === 土木工程學研究所 === 99 === Rock mechanical characteristic is one of the major considering factors of rock engineering design. Caused by the insufficiency of short diagenesis time, part of the stratum in Western Foothill and Coastal Range possess poor cementation and low strength. With the obvious variation of temperature and humidity resulted from the harsh climate, the associate weathering effect leads to remarkable variation in rock mass strength and deformability with respect to time and space, which is harmful to geotechnical engineering. For an engineering construction, problems including time limitation and the unavailability, insufficiency or large variation of rock samples make it difficult to choose proper mechanical parameters. Focusing on clastic sedimentary rocks containing sandstones in central and northern foothill and Paliwan Formation in northern Coastal Range, this study collect related mechanical properties of these rocks, especially the mechanical parameters under man-made humid environment. Using statistical analysis, the variation of mechanical properties of rock samples are investigated through relationships between its physical and microscopic indexes. Noticeable physical and microscopic indexes are identified to suggest representative indexes for weakening and softening phenomena in rock masses. Multivariate analysis is adopted to reduce the possibility of erroneous judgments due to insufficient number and variation of samples and dependency between indexes. The master physical and microscopic factors affecting the mechanical properties and the degree of softening and weakening of clastic sedimentary rocks in Taiwan are then clarified accordingly. Statistical analysis results show that GAR(grain area ratio) and n(porosity) can interpret the RUCS (strength reduction ratio) of the study rock samples. Nevertheless, the statistical results are not good enough due to the instability of the rock samples. Therefore, restarting the statistical analysis without the data of conglomerate. The new statistical analysis results show the stronger relation between the critical factors and mechanical characteristic than before. It is obviously that sandstone and conglomerate should be analysis respectively.