| Summary: | 碩士 === 中原大學 === 土木工程研究所 === 99 === Surcharging is often being used to improve soft soil, and it has great effects on controlling the settlement of soft soil layer. It not only prevents the problems resulted from the differential settlement, but also increases the strength of the soil. In the past, most researches mainly focus on observing the secondary compression after removing the surcharge loading; however, when it comes to real construction, it might remove the whole preloads, followed by reloading due to construction works.
In order to discuss these two different surcharging methods mentioned above, this research uses seven different soils to conduct one-dimentional surcharging tests with different surcharge ratios. The test results are analyzed to evaluate the post-surcharge secondary compression index and the recompression secondary compression index Cαs..
According to the result, the higher the surcharge ratio is, the smaller the post-surcharge secondary compression index will be；however, increases with increasing time and it takes more time for the secondary compression to show up again. The index Cαs decreases with increasing the surcharge ratio. When it’s less surcharged, Cαs will increase with increasing time and it gets steady when the surcharging ratio is 1. The initial strain rate is higher for the recompression secondary compression, therefore, the secondary settlement is also greater. There is an intersection point between the strain rate and time relationships by these two surcharge loading methods, which shows the same rate at the same secondary compression time; in other words, the difference in settlement of the two surcharging methods will appear only before the intersection point.
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