碩士 / 國立交通大學 / 土木工程系所 / 104 / In this study, the effects of soil density on the bearing capacity of the spudcan penetrating submerged sandy soil were investigated. Ottawa sand was used as soil specimen and 1g physical model tests were carried out. The testing facilities constructed at the National Chiao Tung University consisted of the vertical loading system, soil bin, spudcan, and data acquisition system. To simulate the seabed soils with different densities, the air pluviation method was used to prepare uniform soil specimens.Direct shear test results indicated that the peak internal friction angle of Ottawa sand increased with increasing soil density. An empirical relationship between and the peak friction angle and the relative density of soil was proposed. The residual internal friction angle of sand did not change with increasing soil density, and remained 31.7 degree. The dry sand in the soil bin was submerged, and then the air trapped in the submerged soil was removed by a suction of 0.5 atm for 9 hours. Submergence and suction significantly increased the density of the loose sand. However, little density change due to submergence and suction was observed in dense sand. The experimental bearing capacity of the spudcan penetrating soils with different densities were in fairly good agreement with those calculated with the equation suggested by SNAME (2008), using the peak internal friction angle of soil. This finding may be explained by the fact that, during the penetration of spudcan into the seabed, new failure surface were cut continuously in the undisturbed virgin soils, there fore it became necessary to use the peak shear strength of soil to determine the bearing capacity of the spudcan. The amount of ground heaving of the specimen increased with increasing soil density. The ground heaving is probably due to the contraction followed by dilation of dense sand under shearing. The position of maximum ground heaving was located between about 1.3~1.7 times diameter of spudcan from centerline.In the back-flow zone,the measured seabed inclination angle was almost identical to the residual friction angle 31.7 degree of the sand.This is because the soils on both sides of the penetratim zone back flowed to fill the cavaity due to spudcan penetrating . An angle of repose was formed on the surface of the back-flow zone.
| Identifer | oai:union.ndltd.org:TW/104NCTU5015032 |
| Date | January 2015 |
| Creators | Chung,Chi-Hsien, 鍾繼賢 |
| Contributors | Fang,Yung-Show, 方永壽 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 157 |
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