波流作用下海床稳定性和海底管道局部冲刷分析

针对深水油气开采中的海底管道安全铺设与运营问题,总结和归纳了可用于海床稳定性分析及管道周围局部冲刷预测的方法,并推导了水流作用下平衡冲深和悬跨长度间的关系式.在此基础上,利用Fortran和Visual Basic混合编程技术开发了专用分析程序.结合我国南海某工程海域的实际工程问题,对水流、波浪和波流共同作用下的天然底床稳定性进行了分析,同时给出了管道铺设以后,其局部冲刷的垂向极限平衡深度、横向扩展速率以及初级和次级横向扩展的转折点时刻等.结果表明:水流因素对深水区的底床稳定性起主要决定作用;同时若底床泥沙颗粒粒径越小,则其所起的黏性作用就越大,管道冲刷扩展速度越小.该分析结果为实际海底管道路由设计及工程施工方案的制定提供了技术依据.

Analysis of seabed stability and local scour around submarine pipelines under waves and current

For the safety issue of laying and operation of submarine pipelines in deepwater oil exploitation and gas mining,the available theoretical and empirical methods were employed,besides,a relationship between the equilibrium local scour depth and the corresponding spanning length was deduced under current condition.Based on this work,an analysis program was developed,using a mixed-language programming technique which involves Fortran and Visual Basic.The sand stability and the local scour around submarine pipelines were predicted for a practical engineering application in South China Sea.The actions of current,waves and combined waves and current were considered in this work.The stability of seabed before laying pipeline was evaluated using the proposed code,the maximal local scour depth,lateral growing speed and the transition time associated with the local scour were also presented.The results show that the current action takes a decisive role for the bed stability in deepwater region;and a small particle size of bed sediment will contribute a large viscosity which will reduce the pipe erosion rate of expansion.This analysis provides a technical basis for the design of submarine pipeline routings and the formulation of construction schemes.