Stability of Suction Foundation against Eccentric Loading

通过模型试验和有限元分析，阐明了吸力地基抗倾斜荷载承载力的机理。对倾斜荷载条件下的承载力进行了研究。(1)吸力基础水平承载力随内径与外径比值的减小而增大。当D/B=1.1，竖向承载力=44.1N时，水平承载力较标准基础分别降低约40%和50%。2)水平承载力随着D/B的增大和相对密度的增大而增大。3)在吸力基础周围和下方产生楔形应变场。特别是，应变集中在基础附近。4) D/B较小时，基础下地面出现滑动破坏。楔形破坏表现为D/B和倾斜角的增加。拉出破坏表现在滑动破坏和楔形破坏之间。5)在相同荷载条件下，基础位移随D/B的增大和内径与外径比的减小而增大。此外，还进行了模型试验，对偏心荷载作用下的承载力机理进行了评价。总结了吸力基础抗偏心荷载的主要研究结果；1)竖向承载力随加载偏心距的增大而减小。2)随着内外径比的增大，承载能力减小。3)吸力基础的抗剪比由基础的尖角决定。4)加载开始时产生尖部阻力。之后，吸力基础在基础尖端附近形成乳酸，侧阻力逐渐形成。5)偏心距小时，基础附近应变场较大，偏心距大时应变场较大。最后，进行了粘土地面的抽拔试验，阐明了抽吸的产生机理和破坏模式。

In this study, model test and finite element analysis were performed to clarify the mechanism of bearing capacity of suction foundation against inclined loading. The main findings for the bearing capacity against inclined loading condition are followed ;1)Horizontal bearing capacity of suction foundation increases with decreasing ratio of inner diameter and outer diameter. In case of D/B=1.1 and vertical bearing capacity=44.1N, the horizontal bearing capacity decreases about 40 and 50% compared to a standard foundation.2)Horizontal bearing capacity increases as D/B increases and relative density increases.3)Wedge of strain field is generated around and below a suction foundation. Especially, strain is concentrated adjacent to a foundation.4)Sliding failure is shown in ground under the foundation if D/B is small. However, wedge failure is shown as D/B and inclined angle increase. The pull out failure is shown between sliding failure and wedge failure.5)In same loading condition, displacement of foundation increases with increasing D/B and decreasing ration of inner and outer diameter.In addition, the model test is performed to evaluate the bearing capacity mechanism against eccentric loading. the main findings of suction foundation against eccentric loading are followed ;1) Vertical bearing capacity decreases with increasing eccentric distance of loading.2) Bearing capacity decreases as the ratio of inner and outer diameter increases.3) The shearing ratio of resistance for suction foundation is determined by the sharp of foundation.4) Tip resistance is developed at beginning of loading. After that, suction foundation lactates around the tip of foundation and lateral resistance are gradually developed.5) In the case of small eccentric distance, large strain field are shown adjacent to foundation compared to large eccentric distance.Finally, the pull out test using clayey ground is performed to clarify the mechanism of generating suction and failure mode.