黄河废弃水下三角洲地基土对平台插拔桩的响应
发布时间：2019-06-27 20:09
【摘要】：1976年黄河改走清水沟流路后，黄河废弃的钓口流路水下三角洲遭到强烈蚀退，岸滩冲刷很快，水深加大，海岸线大幅度后退，原有沉积地貌单元遭到破坏和夷平。海底滑坡、沉陷、断裂、冲蚀沟槽、差异冲刷、粉土液化等海底不稳定因素均有发生，这些海底不稳定因素对油田开发带来了巨大挑战。海洋石油钻井平台在施工过程中，发生过桩腿刺穿、滑移甚至平台倾覆，造成了灾难性海洋工程事故。 本论文依托多年积累的井场路由调查资料，研究了黄河废弃水下三角洲地基土的强度特征及分布规律。研究区近十年来整体处于冲刷状态，4-10m等深线之间的水下岸坡区平均冲刷大于2m。研究区浅部地基土主要为近期三角洲相的粉土和淤泥、淤泥质粉质粘土和早期的河湖沼泽相的粉质粘土、粉细砂及粉土。海底表层沉积物主要类型有粉土和淤泥、淤泥质粉质粘土。表层粉土，具有较高的力学强度，厚层粉土可以作为插桩式钻井平台的持力层；淤泥、淤泥质粉质粘土属于软弱土，不能满足插桩式钻井平台的要求。河湖相沉积的粉细砂、粉土，厚度一般大于10m，是插桩式钻井平台在该区理想的持力层。 根据地基土破坏的一般形式和特征，分析了桩靴式钻井平台插拔桩过程中地基土的破坏形式和特征。插拔桩过程是动态贯入过程，桩端及桩靴周围地基土体受到强烈扰动，地基土破坏主要以冲剪破坏为主，土中并不出现明显的连续滑动面，该过程与土体静力学状态下土体整体破坏存在较大区别。在分析了插桩过程中土体的破坏形式基础上，根据极限平衡理论，假定破坏面的方法，推导出了均匀和双层地基土中基于被动土压力的插桩阻力计算公式。 极限承载力的分析计算建立在土体整体剪切破坏模式上，给出了土体极限状态下的承载力。本文推导出的均匀土中和双层地基土中的插桩计算公式，建立在土体冲剪破坏模式上，给出了土体冲剪破坏下的插桩阻力。二者与实际插桩阻力存在一定的差距，分别给出了插桩阻力的上限和下限。插桩阻力分析计算过程中采用假设破坏面更接近于插桩过程土体的破坏模式，实例计算结果也表明该方法计算的插桩阻力较以前的极限承载力更接近于实际插桩阻力，丰富了桩靴式钻井平台插桩深度预测方法。 根据插拔桩后井场的调查资料，分析了地基土经历插拔桩过程后的变化特征，探讨了桩坑内土体的强度恢复机理。地基土经历插拔桩过程后，在海底形成一定大小和深度的桩坑，在水动力作用下，桩坑逐渐被夷平。在浅地层声学记录上表现为地层反射面的中断，尚未夷平的桩坑在声纳图像上表现为近视圆形的凹坑。分析结果表明地基土经历插拔桩过程后工程性质发生了较大变化：粉土经历插拔桩过程后，桩穴内的含水量一般小于桩穴外的含水量；桩底下粉土的含水量比周边粉土的含水量小。桩穴内的粉土的压缩模量一般大于桩穴外地基土的压缩模量；软粘土的压缩模量一般小于桩坑周边地基土的压缩模量。研究认为，粉土是研究区桩靴式钻井平台的主要的持力层，具有良好的排水条件，经历插拔桩后的桩坑内的粉土强度一般大于或接近周围土的强度。软粘土由于排水条件很弱，插桩过程中受到扰动破坏，，强度降低。受到扰动的地基土强度恢复过程复杂，影响因素主要有再沉积作用、自身的压缩固结、沙土液化和人工预压。需要重复插桩的井场，地基土变化由于经历了插拔桩的过程较原始地层复杂，为了提高地基土的强度，可以采取预压的方式提高地基土的承载力。 近年来，随着海洋石油的开发活动加剧，研究区内平台插拔桩作业频繁，地基土受到扰动和破坏，从而使得本来就复杂的井场地层情况变得更为复杂。虽然在海洋水动力作用下，地基土强度会恢复，但由于其强度与周边土体强度存在差别，后续平台插拔桩施工作业过程中存在较大的安全隐患。进一步研究受到扰动破坏土体的工程性质变化及其对平台插桩的影响，有助于减少工程事故的发生。
[Abstract]:After the Yellow River was changed to the clear water channel in 1976, the underwater delta of the abandoned fishing-port flow channel of the Yellow River was strongly eroded, and the water depth increased and the coastline greatly retreated, and the original sedimentary geomorphic unit was damaged and flattened. The unstable factors such as the submarine landslide, the subsidence, the fracture, the erosion groove, the differential scouring, the liquefaction of the silt and the like have taken place, and the unstable factors of the seabed have brought great challenges to the development of the oil field. In the course of construction, the offshore oil drilling platform has caused a catastrophic ocean engineering accident. In this paper, the strength characteristics and distribution of the foundation soil of the waste water delta in the Yellow River have been studied based on the survey data of well pads accumulated over the years. Law. The study area is in a flush state in the last ten years, and the average scour of the underwater land area between the 4-10m isobath is greater than the average. The foundation soil in the shallow part of the study area is mainly silt and silt of the near-term delta phase, silty clay of the silt and the silty clay and fine sand of the early river and lake swamps. Silty soil. The main types of surface sediments in the bottom of the sea are silt, silt and silty clay. The silty soil of the surface layer has higher mechanical strength, and the thick layer of silt can be used as the bearing layer of the pile-in type drilling platform; the silt and the silty clay belong to the soft soil and can not meet the pile-in type drilling platform The fine sand, silt and the thickness of the river and lake facies are generally more than 10m. It is the ideal holding platform for the pile-type drilling platform in this area. The general form and characteristics of the base soil failure in the base area are analyzed, and the damage of the foundation soil during the process of the pile-shoe type drilling platform is analyzed. The process of the plug-in pile is the dynamic penetration process, the soil body around the pile end and the pile shoe is strongly disturbed, the damage of the foundation soil is mainly caused by the impact and shear, and no obvious continuous sliding surface appears in the soil, and the process and the soil body in the static state of the soil are damaged as a whole. Based on the analysis of the damage form of the soil in the process of inserting the pile, according to the limit equilibrium theory, the method of the failure surface is assumed, and the plug-in resistance based on the passive earth pressure in the uniform and double-layer foundation soil is derived. The calculation of the ultimate bearing capacity is based on the overall shear failure mode of the soil, and the soil mass is given. In this paper, the calculation formula of the pile-in pile in the soil and the double-layer foundation soil is derived, and the shear-shear failure mode of the soil is established. There is a certain gap between the resistance of the inserted pile and the actual pile-in resistance, and the plug-in pile is given separately. The upper limit and the lower limit of the resistance are calculated. In the process of pile resistance analysis, it is assumed that the failure surface is closer to the failure mode of the soil in the process of inserting the pile, and the calculation results of the example also show that the pile resistance calculated by the method is more than that of the previous limit bearing capacity. It is close to the actual pile-in resistance, and enriches the pile-shoe type drilling platform. According to the survey data of the well pad after the plug-in pile, the change characteristics of the foundation soil after the process of inserting and pulling the pile are analyzed, and the pile-pile depth prediction method is discussed. The strength recovery mechanism of the soil in the pit. After the foundation soil is subjected to the process of plugging and pulling the pile, a pile pit of a certain size and depth is formed on the sea floor, The pile pit is gradually razed under the action of the surface of the formation in the acoustic recording of the shallow formation. The pile pits that have not yet been flattened are in the sonar image. The results show that the water content in the pile cavity is less than the water content outside the pile and the water content of the foundation soil under the pile is less than that of the pile. and the compressive modulus of the soft clay is generally smaller than the compressive modulus of the ground soil outside the pile, and the compressive modulus of the soft clay is generally smaller than that of the pile, The compressive modulus of the foundation soil at the periphery of the pit is studied. The research is that the silt is the main bearing stratum of the research area pile shoe type drilling platform, and has good drainage conditions, and the strength of the silt in the pile pit after the extraction and removal of the pile is generally Greater than or near the strength of the surrounding soil. The soft clay is in the process of pile-in due to poor drainage conditions It is disturbed by the disturbance, and the intensity is reduced. The soil strength recovery process of the disturbed foundation is complicated, and the influencing factors mainly have the effect of re-excitation and the compression and solid of the soil. In order to improve the strength of the foundation soil, pre-pressing can be adopted to improve the strength of the foundation soil. The bearing capacity of the foundation soil is improved. In recent years, with the development of the offshore oil, the operation of the platform plug-in pile in the research area is frequent, and the foundation soil is disturbed and destroyed, so that the foundation soil can be complex The formation condition of the well pad becomes more complicated. Although the strength of the foundation soil can be restored under the action of the ocean water, the construction of the post-platform plug-in pile due to the difference in the strength of the soil and the strength of the surrounding soil There is a great potential safety hazard in the operation process. The change of the engineering property and the shadow of the platform plug-in by the disturbance are further studied.
【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU473.1
本文编号：2507110
[Abstract]:After the Yellow River was changed to the clear water channel in 1976, the underwater delta of the abandoned fishing-port flow channel of the Yellow River was strongly eroded, and the water depth increased and the coastline greatly retreated, and the original sedimentary geomorphic unit was damaged and flattened. The unstable factors such as the submarine landslide, the subsidence, the fracture, the erosion groove, the differential scouring, the liquefaction of the silt and the like have taken place, and the unstable factors of the seabed have brought great challenges to the development of the oil field. In the course of construction, the offshore oil drilling platform has caused a catastrophic ocean engineering accident. In this paper, the strength characteristics and distribution of the foundation soil of the waste water delta in the Yellow River have been studied based on the survey data of well pads accumulated over the years. Law. The study area is in a flush state in the last ten years, and the average scour of the underwater land area between the 4-10m isobath is greater than the average. The foundation soil in the shallow part of the study area is mainly silt and silt of the near-term delta phase, silty clay of the silt and the silty clay and fine sand of the early river and lake swamps. Silty soil. The main types of surface sediments in the bottom of the sea are silt, silt and silty clay. The silty soil of the surface layer has higher mechanical strength, and the thick layer of silt can be used as the bearing layer of the pile-in type drilling platform; the silt and the silty clay belong to the soft soil and can not meet the pile-in type drilling platform The fine sand, silt and the thickness of the river and lake facies are generally more than 10m. It is the ideal holding platform for the pile-type drilling platform in this area. The general form and characteristics of the base soil failure in the base area are analyzed, and the damage of the foundation soil during the process of the pile-shoe type drilling platform is analyzed. The process of the plug-in pile is the dynamic penetration process, the soil body around the pile end and the pile shoe is strongly disturbed, the damage of the foundation soil is mainly caused by the impact and shear, and no obvious continuous sliding surface appears in the soil, and the process and the soil body in the static state of the soil are damaged as a whole. Based on the analysis of the damage form of the soil in the process of inserting the pile, according to the limit equilibrium theory, the method of the failure surface is assumed, and the plug-in resistance based on the passive earth pressure in the uniform and double-layer foundation soil is derived. The calculation of the ultimate bearing capacity is based on the overall shear failure mode of the soil, and the soil mass is given. In this paper, the calculation formula of the pile-in pile in the soil and the double-layer foundation soil is derived, and the shear-shear failure mode of the soil is established. There is a certain gap between the resistance of the inserted pile and the actual pile-in resistance, and the plug-in pile is given separately. The upper limit and the lower limit of the resistance are calculated. In the process of pile resistance analysis, it is assumed that the failure surface is closer to the failure mode of the soil in the process of inserting the pile, and the calculation results of the example also show that the pile resistance calculated by the method is more than that of the previous limit bearing capacity. It is close to the actual pile-in resistance, and enriches the pile-shoe type drilling platform. According to the survey data of the well pad after the plug-in pile, the change characteristics of the foundation soil after the process of inserting and pulling the pile are analyzed, and the pile-pile depth prediction method is discussed. The strength recovery mechanism of the soil in the pit. After the foundation soil is subjected to the process of plugging and pulling the pile, a pile pit of a certain size and depth is formed on the sea floor, The pile pit is gradually razed under the action of the surface of the formation in the acoustic recording of the shallow formation. The pile pits that have not yet been flattened are in the sonar image. The results show that the water content in the pile cavity is less than the water content outside the pile and the water content of the foundation soil under the pile is less than that of the pile. and the compressive modulus of the soft clay is generally smaller than the compressive modulus of the ground soil outside the pile, and the compressive modulus of the soft clay is generally smaller than that of the pile, The compressive modulus of the foundation soil at the periphery of the pit is studied. The research is that the silt is the main bearing stratum of the research area pile shoe type drilling platform, and has good drainage conditions, and the strength of the silt in the pile pit after the extraction and removal of the pile is generally Greater than or near the strength of the surrounding soil. The soft clay is in the process of pile-in due to poor drainage conditions It is disturbed by the disturbance, and the intensity is reduced. The soil strength recovery process of the disturbed foundation is complicated, and the influencing factors mainly have the effect of re-excitation and the compression and solid of the soil. In order to improve the strength of the foundation soil, pre-pressing can be adopted to improve the strength of the foundation soil. The bearing capacity of the foundation soil is improved. In recent years, with the development of the offshore oil, the operation of the platform plug-in pile in the research area is frequent, and the foundation soil is disturbed and destroyed, so that the foundation soil can be complex The formation condition of the well pad becomes more complicated. Although the strength of the foundation soil can be restored under the action of the ocean water, the construction of the post-platform plug-in pile due to the difference in the strength of the soil and the strength of the surrounding soil There is a great potential safety hazard in the operation process. The change of the engineering property and the shadow of the platform plug-in by the disturbance are further studied.
【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU473.1
【引证文献】
相关硕士学位论文 前1条
1 马彬彬;暴风浪作用下海底粉土液化研究[D];国家海洋局第一海洋研究所;2015年
本文编号：2507110
本文链接：https://www.wllwen.com/guanlilunwen/chengjian/2507110.html
