【作者】 来向华；

【导师】 陈云敏； 叶银灿；

【作者基本信息】 浙江大学 ， 岩土工程， 2009， 博士

【摘要】 随着油气资源的快速开发,海底管道被广泛地用来输运油气、输水和排污等,成为重要的海上生命线工程。由于海洋环境复杂多变和人类海上活动日益频繁,海底管道的破坏屡有发生,海底管道的安全性受到人们的重视。本文在国家自然科学基金“海浪荷载作用下海底粉质土力学特性的试验研究及应用(10372089)”的资助下,结合杭州湾海底管道工程,对海底管道的原位检测技术,以及海床-管道系统对水动力的响应等方面进行了研究。系统分析了单波束测深、多波束测深、浅地层剖面仪和侧扫声纳等声学探测技术在海底管道原位检测中的应用,探讨了水深和设备技术指标等因素对管道的现场检测能力的影响。结合多波束测深系统特点,提出基于海底微地貌和管道特征的改进IDW算法,能够构建更高精度的DTM,为运用多波束技术检测海底管道奠定基础。针对仪器设备的不同工作原理,开发了海底管道检测数据处理集成技术,极大提高了工作效率和综合利用多种检测技术的能力,并已多次成功运用于我国大型海底管道检测工程。在分析海底管道冲刷-自埋机理基础上,采用数值模拟方法对其中几个关键状态进行分析,利用海底管道现场检测技术,查明杭州湾海底管道敷设至完全掩埋各个阶段的原位状态,首次用现场资料验证了海底管道冲刷至掩埋的演变过程,完善了冲刷至掩埋的演变机制。建立基于采用有限体积法的分离算法求解波浪作用下海床弹性响应的数值模型,并和解析解对比。数值结果和解析解吻合,为进一步研究有管道海床的弹性响应以及液化问题奠定了基础。采用HX-100动三轴系统对杭州湾海底管道路由区结构性海洋粘性土原状样进行了室内试验,试验中采用低循环剪应力比和大振次的方法来模拟波浪荷载,通过对试验数据的分析建立了结构性海洋粘性土孔压发展模型。在海底土孔压发展模型的基础上,结合能反映孔压累积和消散的固结方程,获得了波浪作用下一维海洋粘性土中孔压发展的解析解。分析了波浪参数和土性参数对一维海床中长期累积孔压发展的影响,认识到由于波浪荷载特性和海底表层的完全排水作用,累积孔压会在海底土体的浅部形成峰值,峰值大小和位置随着时间和土体的排水特性的变化而变化。结合波浪场产生的底压力边界条件,通过求解基于Biot固结理论的孔压累积消散方程,能模拟二维有管道海床中瞬态孔压的振荡累积过程。通过对基于Biot固结理论和Terzaghi固结理论获得的孔压累积消散方程的比较,发现由二者计算得到的长期累积孔压非常接近,但后者求解方便,更适合工程应用,因此在后者的基础上探讨了成层海床、含充填河谷海床以及有管道海床中的长期累积孔压特性和液化特征。研究表明,波浪荷载作用下,由海洋粘性土组成的海床上部如果夹有砂质夹层,或砂质海床上部有薄层海洋粘性土覆盖层,砂质土层中的累积孔压会急剧上升,容易导致液化的产生;相反,风暴作用停止后,与砂类土相比,海洋粘性土中的残余孔压消散较慢,CPT实测结果也证明了这一结论。含充填河谷海床以及有管道海床因土性的差异而造成累积孔压发展规律和液化特征与均质海床有较大区别,如果管道槽中的回淤土为砂类土,而原始海床为海洋粘性土,则管道槽周围不易发生液化;如果管道槽中的回淤土为海洋粘性土,而原始海床为砂类土,则在管道槽的两侧和槽底等两类土的界面处易发生液化。更多还原

【Abstract】 The rapid development of offshore oil fields has increased the construction of submarine pipeline for transport of crude oil to onshore refineries, and the submarine pipeline has become one of the lifeline of marine resources. Failure of submarine pipeline will inevitably lead to financial losses and adverse environmental problems, so people pay more and more attentions on the pipeline securities. According to the program supported by NSFC, testing research on the engineering properties of submarine silty clay under wave-induced load and its applications (No. 10372089), this thesis analyses the methods of pipeline inspection, responses of seabed-pipeline system under wave-induced load based on the Hangzhou Bay Pipeline Crossing Project.The survey equipment used in pipeline inspection, such as single beam echo sounder, multi-beam echo sounder, side scan sonar and sub-bottom profiler, are analyzed. According to the features of micro-geomorphology of seabed and pipeline, a method based on inverse distance weighted (IDW) algorithm to construct seafloor digital terrain model (DTM) using multi-beam soundings, which can improve the ability of multi-beam echo sounder on pipeline inspecting. Restricted by the principle of operation, single survey equipment can just quantify one aspect of pipeline burial state. An integrating technology of multi-equipment pipeline inspecting is developed for improving the pipeline inspecting ability and efficiency, which has been verified in several pipeline inspecting projects.Based on the analysis of the mechanism of the self-burial, several key burial states are discussed using numerical modeling method. The in situ states of submarine pipeline in Hangzhou Bay in the processing of self-burial are inspected base on the methods discussed in this thesis. The processing self-burial of pipeline with spoiler is verified by the pipeline inspecting methods discussed in this thesis firstly and the mechanism of the self-burial processing is complemented and verified.A segregated solution algorithm of based on finite volume is applied to analyze the elastic response of the seabed under wave-induced load. Compared with the analytical solution, it is concluded that the numerical results are near consistent with analytical solution. The influences of the characters of wave and soil are discussed based on the numerical results.The cyclic triaxial testing system, HX-100, was carried out on undisturbed soil samples which are interbedded with clay and silt drilled from Hangzhou Bay. Low cyclic shear stress (CSS) and a great deal of numbers of cyclic are adopted in the testing to simulate the wave-induced load, and the pore water pressure buildup curve can be gained from analysis of the testing data. Development characteristics of the pore pressure can be evaluated based on the consolidation equation combined the model of the pore pressure gained from the testing data which can represent the process of generating and dissipating of the pore water in the seabed. An analytical solution of above equation of one dimension is gained. The effects of the soil and wave characteristics on the pore pressure buildup are analyzed under one dimension and it can be drawn that the buildup of pore water pressure displays a maximum value in the upper soils, and the position and the value of it are variable with the storm duration and drain conditions of the soil.The accumulation of the pore pressure with a small range fluctuations can be simulated based on the consolidation equation which can represent the process of generating and dissipating of the pore water in the seabed. The comparison of results of equations derived from the Biot consolidation theory and Terzaghi consolidation theory respectively suggested the residual pore pressure is nearly same after long wave duration. But the latter is convenient for engineering purpose. The characteristics of the residual pore pressure and the possibility of the liquefaction in the layered seabed, infilled channel and infilled pipe trench are analyzed based on the latter equation. The residual pore pressure accumulates quickly and even liquefaction can occur if the drainage is prevented by a clay layer on top of the sand or sand layer embedding clay layers. On the contrast, the dissipating of the pore water in the marine cohesive soil is slow than that in the sandy soils after the end of storm, and which is verified by CPT conducted in the Hangzhou Bay. The development of the pore pressure in the infilled channels and the infilled pipe trench is quite different from that in the homogeneous seabed. If the original seabed is composed of marine cohesive soil and the natural infilled sediment is sand, the zone around the pipeline trench is not easy to undergo liquefaction, while the original seabed is composed of sand and the natural infilled sediment is marine cohesive soil, the soils under the pipeline trench is easy to undergo liquefaction.更多还原