碩士 / 國立交通大學 / 土木工程系所 / 107 / In this study, the mitigation of spudcan-footprint interaction in sand with infilling method was investigated by 1g physical model tests. Ottawa sand was used as soil specimen, and the diameter of the model spudcan was 200 mm. To simulate a uniform seabed material, the air-pluviation method was used to control the distribution of the soil density in the soil bin. After reaching the desired specimen thickness of 0.9 m, water was introduced from the base of dry sand specimen. Then, the remaining air in the flooded sand sample was removed by a constant suction pressure of 50 kPa for 8 hours. In this study, the purpose of the first penetration of spudcan into the soil specimen was to create an existing footprint. Then, the spudcan was repenetrated into three types of seabed conditions: (1) into the footprint; (2) into the infilled footprint; and (3) into the infilled footprint covered with a thin sand blanket. To investigate the effects due to re-penetration offset, four categories of offset distance were conducted: 0, 0.25 D, 0.5 D, and 1.0 D conducted in this study.
Experimental results indicated, due to the existence of the footprint, re-penetration at the center of the footprint would cause no vertical force at the beginning stage of re-penetration. During the first penetration, soil beneath the footprint was compressed and a volumetric contraction occurred. The void ratio of soil decreased and its unit weight increased. Therefore, for the re-penetration, as the spudcan touched the soil surface, the vertical force increased rapidly. After adopting the footprint infilling method, for the offset distances used, infilling method would increase the maximum vertical force about 5% to 20%. For the spudcan to re-penetrate a footprint, maximum horizontal force and bending moment would occur at the offset distance of 0.25 D. As the penetration depth reached 0.2 D, two infilling method used in this study could effectively reduce the maximum horizontal force. At the optimum offset distance 0.25 D and 0.5 D, maximum horizontal force could be reduced for 73% to 76%. At the offset distance of 0.25 D, the maximum bending moment that acting on the spudcan could be reduced for about 63%.
| Identifer | oai:union.ndltd.org:TW/107NCTU5015003 |
| Date | January 2018 |
| Creators | 施映竹 |
| 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 | 184 |
Page generated in 0.0015 seconds