Liquefaction Resistance of Low Plasticity Fine-Grained Soil

• Main Authors: Meng-Heng Chiang, 江孟衡
• Other Authors: Louis Ge
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/07270473395358531075

碩士 === 國立臺灣大學 === 土木工程學研究所 === 101 === There are many factors affecting soil liquefaction including soil density, confining pressure, over-consolidation ratio, plasticity, mineralogy, and particle shape, etc. This research examined liquefaction behavior of non-plastic and low-plasticity silts by a series of cyclic triaxial tests. Materials used in this study were quartz powder and Tieliku silt, which both pass #200 sieve (0.074mm), Specimens were prepared by moist tamping. All tests were carried out under the same initial confining pressure with different dry densities, plasticity indexes and loading rates. From the test results, it can be found that the liquefaction resistance of the quartz powder increased as its dry density increased. The results of Tieliku silts show that the liquefaction resistance decreased as the plasticity index increased under the same initial confining pressure. In addition, silts with different plasticity indexes lead to different liquefaction behaviors. For the specimens with lower plasticity index, specimens first reached the state of zero effective stress, indicating the occurring of the initial liquefaction. It was then followed by the state of 5% double amplitude axial strain during undrained cyclic loading. On the other hand, for the specimens with higher plasticity index, specimens reached 5% double amplitude axial strain first, and then reached the state of zero effective stress or not reached the state at all. This study also investigated the effect of loading rate on liquefaction resistance. According to the test results, for quartz powder with higher permeability, whether the loading rate was fast or slow, its resistance was almost the same and the pore water pressure generation within the specimen was in a similar pattern. It indicates that the liquefaction resistance of quartz powder with higher permeability will not be affected by loading rate. However, for low plasticity silts with lower permeability, the liquefaction resistance decreased as the loading rate decreased and the pore water pressure generation in the specimen followed different patterns. It suggests that the liquefaction resistance of low plasticity silts with lower permeability will be affected by loading rate.