Fundamental Research on a development of CFRP Riser Pipe for 4000 m Deep Sea Scientific Drilling

日本建造了深海科学隔水管钻井船“地球号”，计划在不久的将来钻探4000米水深的海底以获取地幔。然而，在水深4000 m处使用钢立管几乎是不可能的，需要发展CFRP立管。CFRP提升管的关键部件是其机械结构，CFRP管通过几对相互接触的螺纹在管端与钢连接件连接。本文研究的是该类CFRP提升管的研制。在2005年的研究中，采用有限元方法分析了机械结构的形态和尺寸参数变化及其对机械结构强度的影响，并对CFRP提升管进行了机械结构优化。对优化后的CFRP隔水管的轴向振动特性进行了研究，证实了隔水管与钻井船的升沉没有共振。在2007年的研究中，制作了具有优化尺寸的拉伸试验模型并进行了试验，得到了该模型的拉伸强度、伸长率和应变。基于CFRP管段损伤观察，在假设裂纹扩展通过的情况下，通过有限元分析得到实验应变与计算应变之间的相关性，明确了力学结构的断裂过程。在此基础上，总结了4000m深海CFRP提升管的设计思路。

A deep sea scientific riser drilling vessel "Chikyu" was constructed in Japan and it is planned to drill the sea floor at the water depth of 4000 m to obtain the mantle in the near future. However, it is almost impossible to use the steel riser pipe at the water depth of 4000 m and the development of CFRP riser pipe is desired. The key element of the CFRP riser pipe is its mechanical structure where the CFRP pipe is connected at the pipe ends to the steel connectors through several pairs of mutually contacting threads. This research is concerned with the development of this type of CFRP riser pipe.In the research of 2005, the configuration and dimension of the mechanical structure were parametrically changed and their influence on the strength of the mechanical structure was made clear using FEM analysis and the optimization of the mechanical structure of the CFRP riser pipe was performed. The characteristic of the axial vibration of the optimized CFRP riser pipe was also studied and it was confirmed that the riser pipe had no resonance with the heaving of the drill ship.In the research of 2007, a tensile test model, which had the optimized dimension, was fabricated and tested and its tensile strength, elongations and strains were obtained. The fracture process of the mechanical structure was made clear from the correlation between the experimental strains and the calculated strains which were obtained from FEM analysis with assuming crack propagation passes based on the damage observation of the CFRP pipe section.Based on the results stated above, the thinking concerning the design of the CFRP riser pipe for 4000 m deep sea has been summarized.