南海北部陆坡神狐海域峡谷区黏性土海底滑坡过程及其动力学机制研究

海底滑坡过程是深水陆坡区块体搬运沉积体系研究与海底管道安全评价的关键内容，现有滑坡数值模型尚不能完全反映海底斜坡变形-破坏-滑动的整体过程，给科学研究与工程评价带来一定的不确定性。本项目针对我国南海北部陆坡神狐海域峡谷区，从力学角度开展黏性土的海底滑坡过程及其动力学机制研究。采用近年兴起的耦合欧拉-拉格朗日大变形有限元方法，基于大剪切位移条件下黏性土强度的应变软化与速率相关特性试验研究，构建一种新的黏性土海底滑坡全过程数值模型，并通过与水槽实验对比验证数值方案的有效性；针对峡谷不同位置典型海底滑坡识别特征开展数值反分析计算，定量研究滑坡过程中土体的变形特征以及环境水对滑坡体动态特性的影响规律，明确滑坡沉积特征对关键工程地质参数的响应关系，揭示目标区黏性土海底滑坡过程的动力学机制。项目研究成果可以为我国南海北部陆坡海底滑坡地质灾害定量评价与防治提供理论与技术储备。

The submarine landslides process has been considered to be the key content for the mass transport deposits research and pipeline safety risk assessment in the deep-water slope area. The existing numerical models can’t reflect the whole evolution of the submarine landslide from slope deformation to slope failure to mass movement, which may lead to certain uncertainty for the pertaining scientific research and engineering evaluation. In this proposal, taking the Shenhu canyon area of the northern slope of the South China Sea as the target area, we focus on the cohesive soil submarine landslides process and its dynamics mechanism from the mechanics perspective. The coupled Eulerian- Lagrange finite element method rising in recent years is used to establish a new numerical process model for the cohesive soil submarine landslides. In this new model, the strain-softening and rate-dependency of the undrained shear strength of the cohesive soil, obtained from shear test under large shear displacement condition, is taken into account. The validity of the established model will be verified by comparison with the flume experiment result. According to the identification characteristics of typical submarine landslides located at different positions of the canyon, the quantitative study of the soil deformation characteristics and the influence of ambient water on the landslide mass are conducted by using numerical back-calculation method, and then the response relationship between deposition characteristics of submarine landslides and key engineering geological parameters can be setup based on the numerical results. Finally, the dynamics mechanism of the cohesive soil submarine landslides in the target area can be revealed through the above comprehensive analysis. The research results can provide theory and technique reserve for the quantitative evaluation and prevention of submarine landslide in the northern slope of the South China Sea.