台风海况下深水平台锚泊基础连续失效机制与分析方法

我国南海台风多发，深水区油气资源丰富，油气工程开发迫切需要解决深水浮式平台的锚泊系统安全问题。深水锚泊系统通常由张紧/半张紧的多根锚泊线和相应的锚泊基础（吸力锚、平板锚）组成。已有的墨西哥湾和欧洲北海大量走锚事故表明：锚泊系统在极端海况下存在着各锚点多米诺式连续失效的巨大风险。本项目拟针对典型深水锚泊系统，联合运用理论分析、数值计算、室内试验和现场试验等手段，开展以下研究：分析掌握循环动力加载、循环剪切-重固结作用下深海土的强度演化特性，建立工程实用的本构模型；研究阐明悬张锚泊线-海床土体的循环动力作用过程，厘清锚泊线触底区的冲刷开槽机制；分析锚泊基础上循环动力和出平面加载特性，考虑锚泊线触底开槽效应，研究揭示台风海况下锚泊基础的拔出破坏机制；分析评估单根锚泊线破断后剩余各锚点的连续失效机制，提出台风海况下锚泊系统的安全评价方法。项目研究成果将为我国南海深水锚泊系统设计提供必要的科学依据。

Despite the abundant oil and gas resources in South China Sea, the frequent occurrence of typhoons has been threatening the deep-sea mooring systems for oil and gas platforms. The exploration of oil and gas in South China Sea has therefore necessitated the urge to address the safety of the deep-sea mooring systems, which usually consist of taut/semi-taut multiple mooring lines and anchor foundations (suction anchor and plate anchor) on the seabed. The existing large number of catastrophes in the Gulf of Mexico and the European North Sea has evidenced the great potential of progressive failure for all anchor foundations under the extreme typhoon conditions. For the above reasons, a systematical study including theoretical analysis, numerical simulation, laboratory experiments and field validation is proposed herein, with the principal objectives to (a) understand the degradation behaviour of typical soft marine soils under episodes of cyclic loadings with intervals of reconsolidation, and propose simplified constitutive models for engineering practice; (b) study the dynamic interaction between mooring lines and seabed soil, and reveal the mechanism of scouring and trenching in the touch down zone of the mooring lines; (c) reveal the pullout failure mechanism of anchor foundation subjected to dynamic out-of-plane loadings, with simultaneous occurrence of local trench in the touch down zone of the mooring line; (d) evaluate the risk of progressive failure in the remaining anchors following the breakage of one mooring line, and propose a scientific approach for accessing safety of deep-sea mooring system under extreme typhoon conditions. The research outcomes of this project would address some of the key scientific challenges involved in the design of deep-sea mooring system against the typhoon loadings in South China Sea.