自升式钻井平台桩靴踩脚印应对措施对比研究

Comparative research on measures for mitigating the interactions of spudcan-footprint during spudcan of jack-up rigs penetrating next to an existing footprint

基于现有规范与文献研究提出的减小桩靴踩脚印附加响应的相关措施,首先基于耦合欧拉-拉格朗日(CEL)定量分析了传统纺锤形桩靴与新型桩靴在不同工况条件下插桩时桩靴地基土体相互作用机制,明确了最不利桩靴踩脚印工况时的插桩偏心距与桩坑深度。基于该最不利工况条件,对比分析了新型六孔莲蓬形桩靴、试踩法与地基钻孔法3种桩靴踩脚印应对措施的适用性与有效性。结果表明,相较于传统纺锤形桩靴,采用六孔莲蓬形桩靴使桩靴倾斜角与桩腿偏移距分别降低了33.13%和48.26%,说明结构在位稳定性更高。此外,通过对比分析得出,采用最佳设置方式进行试踩与钻孔处理后再进行桩靴贯入时,桩靴受到的水平滑动力峰值与桩腿RP_(1)处弯矩峰值相较于未处理时分别降低了29.47%、29.17%、34.7%、37.7%。可见,3种应对措施均能有效降低桩靴踩脚印后产生的不利影响,提高桩靴结构的在位稳定性。以最终减小不利附加响应程度作为评定标准:地基钻孔法>新型六孔莲蓬形桩靴>试踩法,由于地基钻孔法与试踩法均需增设额外机械设备及施工工序,大幅提高了工程造价,因此,在实际工程中,需要根据实际情况恰当选择应对措施。研究成果可为实际工程中应对桩靴踩脚印工况响应提供一定参考与借鉴。

Based on the measures proposed by the existing codes and literatures to reduce the additional responses of spudcan during its penetrating next to an existing footprint,firstly,we analyzed different mechanisms of spudcan-soil interactions between the traditional spindle-shaped spudcans and the novel spudcans quantitatively under kinds of working conditions based on the finite element method of CEL,and the eccentric distance and the depth of footprint for the worst operating conditions were determined.Based on such working conditions,the applicability and effectiveness of three countermeasures to spudcan-footprint interactions,that is,the new six-hole lotus-shaped spudcan,stomping method and perforation drilling near an existing footprint method,were compared and analyzed.The results show that the six-hole lotus-shaped spudcan can reduce the inclination angle and the offset distance of the spudcan by 33.13%and 48.26%,respectively,compared with the traditional spindle-shaped,indicating that it is more stable in-situ.In addition,it is also concluded that the peak horizontal sliding force and the peak bending moment at RP_(1) of the pile leg subjected by spudcan are reduced by 29.47%,29.17%,34.7%,and 37.7%,respectively,when stomping method and perforation drilling method are adopted,compared with the case without any treatment.It can be seen that all three measures can effectively reduce the adverse effects generated by spudcan-footprint interactions so as to improve the in-situ stability of the spudcan structure.The degree of final reduction of adverse additional response is used as the evaluation criterion:foundation drilling method>new six-hole rosette-shaped spudcan>test tread method.However,both the stomping method and the perforation drilling method require additional mechanical equipment and construction procedures,which significantly increase the project cost,so it is necessary to select the most optimal countermeasures based on the actual situation in the actual project.The research results of this paper can provide some references for the practical project to mitigate the interactions of spudcan-footprint during the process of spudcan of jack-up rigs penetrating next to an existing footprint.