| 摘要: |
| 为了降低自升式钻井平台在旧桩坑附近插桩时可能产生的工程风险,本文开展了一系列桩靴结构型式的优化研究和对比分析,提出六孔莲蓬形桩靴、平底桩靴、内凹形桩靴三种新型桩靴结构型式。首先借助CEL分析方法研究了上述桩靴结构在偏心距为0.5D的踩脚印贯入过程中桩靴-地基土体相互作用机制、受扰动土体的塑性变形水平范围及桩靴倾斜角和桩腿偏移距等与传统桩靴结构的差异,并采用有限元法及规范计算法对比分析了桩靴结构承载特性,最后评估了上述桩靴结构在成层土地基插桩过程中发生穿刺事故的风险。结果表明,相同踩脚印工况下,六孔莲蓬形桩靴、平底桩靴、内凹形桩靴三种新型桩靴结构产生的水平滑动力、桩腿顶部弯矩峰值相较于传统纺锤形桩靴结构降低值依次分别为32.59%、22.47%、28.18%和26.32%、12.88%、18.02%。可见,三种新型桩靴结构型式均能较好地降低桩靴踩脚印过程中产生的不利影响,其中六孔莲蓬形桩靴降低效果最好,内凹形桩靴次之,但后者结构型式更为简单,制作方便。其次,若考虑到降低桩靴贯入对邻近导管架平台的影响,六孔莲蓬形桩靴结构因对周围土体扰动影响最小而效果最佳。若考虑到桩靴在成层土或不连续贯入插桩作业时发生穿刺事故的可能性,当施加相同的稳定荷载并插桩到相同深度时,平底桩靴发生穿刺事故的可能性更小。本文研究成果可为实际工程设计提供一定参考和借鉴。 |
| 关键词: 踩脚印工况 新型桩靴 VHM曲线 桩靴倾斜角 桩腿偏移距 |
| DOI： |
| 分类号:TU431 |
| 基金项目:重庆市博士后科研项目特别资助项目(Xm2017188)；国家重点研发计划项目(2018YFB1600400)；中国地质调查项目(DD201892700)；重庆市基础与前沿研究科学基金(cstc2018jcyjAX0559). |
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| Research on optimization design of spudcan structure for mitigating spudcan-footprint interaction |
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helinlin,yangliu,fengchujie,liangyue
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Chongqing Jiaotong University
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| Abstract: |
| In order to ease spudcan-footprint interactions during jack-up rigs penetrating in the vicinity of an existing seabed footprint, three new spudcan shapes, a six-hole lotus-shaped spudcan, a flat-bottomed spudcan, and a concave-shaped spudcan, were proposed and analyzed comparatively to carry out optimizing study of the spudcan structure.Firstly,large-deformation finite element (LDFE) was performed using the Coupled Eulerian-Lagrangian(CEL) method with the idealized elastic-plastic Tresca model to analyze differences between the innovative spudcan shapes and the traditional one in interaction mechanism of spudcan-soil during spudcan penetrating next to an existing footprint with an eccentricity of 0.5D, as well as the horizontal range of plastic deformation of the disturbed soil, the inclination angle of spudcan and the offset of the pile leg. Then FEM method and the method of Specification were used to evaluate the bearing capacities of different spudcan structures. Finally, the risk of puncturing was assessed during different spudcans penetrating in the layered soil. The results show that the six-hole lotus-shaped spudcan, flat-bottom spudcan, and concave-shaped spudcan can mitigate the horizontal sliding force and peak bending moment at the top of the pile leg compared with those of traditional spindle-shaped piles obviously, and which are reduced by 32.59%, 22.47%, 28.18%, and 26.32%, 12.88%, 18.02%, respectively. It can be seen that all the new spudcan structures can ease the adverse consequences of the spudcan-footprint interactions effectively. Among them, the six-hole lotus-shaped one works best, and the concave-shaped one is slightly less but simpler and easier to produce. Besides, considering impact of spudcan penetrating on the adjacent jacket platform, the six-hole lotus-shaped spudcan structure is priority due to the least horizontal range of soil disturbance. In view of the risk of puncturing when spudcans penetrating into the layered soil or discontinuously, the flat-bottomed spudcan is priority due to the least possibility of puncturing when the same stable load is applied and the spudcan is penetrated into the same depth. The results of this paper can provide some references for practical engineering design. |
| Key words: Spudcan-footprint interaction new spudcan VHM curve inclination angle of spudcan offset of pile leg |
