非连续压载下黏土层中桩靴承载力变化规律
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摘要
设计了一套自升式钻井平台大桩靴插桩模型试验装置,通过改变桩靴加载过程中的加载速度,观测桩靴承载力与加载速度之间的关系,探讨非连续压载工况下软黏土层中桩靴承载力的变化规律和发生快速下沉的原因。研究结果表明:在软黏土层中桩靴会发生快速下沉现象;土体固结导致土体抗剪强度增加,从而产生的"人工硬层"是桩靴发生快速下沉的主要原因;加载速度对桩靴下沉有较大影响,加载速度越快,桩靴越容易发生快速下沉,因此在工程实际操作过程中可通过降低压载速度来减小穿刺发生的风险。
A model test device for simulating the inserting process of large spudcan of jack-up drilling rig has been designed to observe the relationship between bearing capacity and loading speed of spudcan by changing the loading speed during the ballasting and to give an insight into the variation law of the bearing capacity of spudcan in soft clay layer and the causes for rapid sinking of spudcan under the condition of discontinuous ballasting.The research results show that the spudcan will rapidly sink in the soft clay layer;the soil consolidation leads to an increase in the shear strength of the soil,and the resulted"artificial hard layer"is the main reason for the rapid sinking of spudcan;the loading speed has an obvious influence on the sinking of spudcan.The faster the loading speed,the more likely the spudcan will sink rapidly.Therefore,the risk of puncture can be alleviated by reducing the loading speed during the actual ballasting operation.
A model test device for simulating the inserting process of large spudcan of jack-up drilling rig has been designed to observe the relationship between bearing capacity and loading speed of spudcan by changing the loading speed during the ballasting and to give an insight into the variation law of the bearing capacity of spudcan in soft clay layer and the causes for rapid sinking of spudcan under the condition of discontinuous ballasting.The research results show that the spudcan will rapidly sink in the soft clay layer;the soil consolidation leads to an increase in the shear strength of the soil,and the resulted"artificial hard layer"is the main reason for the rapid sinking of spudcan;the loading speed has an obvious influence on the sinking of spudcan.The faster the loading speed,the more likely the spudcan will sink rapidly.Therefore,the risk of puncture can be alleviated by reducing the loading speed during the actual ballasting operation.
引文
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[2]SKEMPTON A W.The bearing capacity of clays[J].Thomas Telford,1984.
[3]HOULSBY G T,MARTIN C M.Combined loading of spudcan foundations on clay:laboratory tests[J].Geotechnique,2000,50(4):325-338.
[4]HOSSAIN M S,RANDOLPH M F.New mechanism-based design approach for spudcan foundations on single layer clay[J].Journal of Geotechnical&Geoenvironmental Engineering,2009,135(9):1264-1274.
[5]张爱霞.方形桩靴自升式平台地基极限承载力及结构抗穿刺研究[D].大连:大连理工大学,2013.ZHANG Aixia.Ultimate bearing capacity of jack-up with square spudcan and application to structure investigation against punch-through[D].Dalian:Dalian University of Technology,2013.
[6]中华人民共和国国家发展和改革委员会.SY/T6707—2008海洋井场调查规范[S].北京:石油工业出版社,2008.
[7]SNAME.Guidelines for site specific assessment of mobile jack-up units,technical and research bulletin5-5a[S].New Jersey:SONA Engineers,2008:64.
[8]PURWANA O A.Centrifuge model study on spudcan extraction in soft clay[D].Singapore:National University of Singapoore,2006.
[9]BARBOSE-CRUZ.Partial consolidation and breakthrough of shallow foundations in soft soil[D].Perth,Australia:University of Western Australia,2007.
[10]BIENEN B,CASSIDY M J.Set up and resulting punch-through risk of jack-up spudcans during installation[J].Journal of Geotechnical&Geoenvironmental Engineering,2013,139(12):2048-2059.
[11]BENEN B,RAGIN R,CASSIDY M J,et al.Effects of consolidation under a penetrating footing in carbonate silty clay[J].Journal of Geotechnical&Geoenvironmental Engineering,2013,141(9):04015040.
[12]WANG D,BIENEN B.Numerical investigation of penetration of a large-diameter footing into normally consolidated kaolin clay with a consolidation phase[J].Géotechnique,2016,66(11):1-6.
[13]高攀,段梦兰,赵良美,等.大比尺自升式平台插拔桩试验系统研制及验证[J].中国海上油气,2016,28(6):108-114.DOI:10.11935/j.issn.1673-1506.2016.06.018.GAO Pan,DUAN Menglan,ZHAO Liangmei,et al.Development and validation of a large-scale model test system for spudcan penetration and extraction[J].China Offshore Oil and Gas,2016,28(6):108-114.DOI:10.11935/j.issn.1673-1506.2016.06.018.