碩士 / 國立交通大學 / 土木工程系所 / 105 / In this study, the effects of layered sand on the bearing capacity of the spudcan were investigated. Ottawa sand was used as soil specimen to conduct 1g physical model tests for the model spudcan with a diameter of 100 mm. Testing facilities used 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 three densities (Dr = 26%, Dr = 51% and Dr = 85%), the air pluviation method was used to prepare the 900 mm-long, 900 mm-wide and 900 mm-high dry soil specimens. After the specimen was submerged in the soil bin, the air trapped in the specimen was removed by a suction pump. Tests were conducted to investigate the degree of saturation of the specimen. Test results indicated that, after submergence and suction, the degree of saturation of the specimen reached 99.97±0.14%. Four different types of layered-sand specimens were prepared: (1) upper layer with relative density Dr = 85% and lower layer with Dr = 26%; (2) upper layer with Dr = 51% and lower layer with Dr = 26%; (3) upper layer with Dr = 26% and lower layer with Dr = 85%; (4) upper layer with Dr = 26% and lower layer with Dr = 51%. Test results indicated that the experimental bearing capacities were about 0 to 20% higher than those calculated with the equation suggested by SNAME(2008). The experimental bearing capacities obtained with centrifuge model tests by Lu(2007) were also higher than the values estimated with SNAME. In the equation of SNAME, it was assumed that the volume, relative density and shear strength of soils in the upper and lower layers were kept a constant. However, during the penetration and lifting of spudcan in the soils, volume contraction in loose sand and dilation in dense sand would occur when sheared. Change of volume, density, and shear strength due to shearing was probably the main reason that caused the different bearing capacity curves between theoretical and experimental studies. For a model spudcan penetrating sandy soils with different densities, the depth of failure surface in soil was about 1.0D to 1.2D
| Identifer | oai:union.ndltd.org:TW/105NCTU5015023 |
| Date | January 2016 |
| Creators | Chen,Sheng-Lin, 陳聖麟 |
| 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 | 148 |
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