线性波浪加载下海底斜坡失稳机制的数值分析

Numerical Analysis of the Failure Mechanism of Submarine Slopes under Linear Wave Loading

基于大型有限元软件ABAQUS中的荷载模块,添加一阶波浪力载荷模式,并结合强度折减技术,实现波浪力作用下海底斜坡稳定性与失稳机制的弹塑性有限元数值分析。引入典型算例,利用先前提出的波浪荷载下海底斜坡稳定性的极限分析上限方法开展数值解的对比验证;在此基础上,通过深入地变动参数比较分析,探讨不同波长、波高和水深等波浪参数对计算结果的影响以及波浪力影响下海底斜坡潜在滑动面的变化规律,获得波浪荷载下海底斜坡失稳滑动机制的初步认识。

Submarine landslides,a natural hazard,not only destroy subsea infrastructure but also trigger life-threatening tsunamis.Because of its destructive potential,many scholars are studying the failure mechanism of seabed slopes.There are many factors that induce submarine landslides,e.g.,earthquakes,volcanic eruptions,gas hydrate dissociation,and so on.However,the instability of the seafloor in shallow waters may be induced by waves.This study treats the stability of a submarine slope as a plane strain problem and adopts an elasto-plastic constitutive model obeying the Mohr-Coulomb yield criterion.To analyze seafloor stability under wave loading,a large-scale elasto-plastic finite element program called ABAQUS combined with a strength reduction method is adopted.Based on linear wave theory,wave-induced pressure is implemented by developing a loading module in this program.Pressures are applied on the slope surface as pseudo-static loads at a particular time during the wave period.In addition,a typical example is presented,and a factor of safety（FS）and corresponding critical sliding surface（CSS）for the submarine slope under wave loading are obtained using the improved finite element program.A previously programmed analytical code based on an upper-bound approach of limit analysis is also employed to validate the numerical solutions.Based on this,a series of comparative analyses is performed.The effect of wave parameters such as wave length,wave height,and water depth on slope stability and the positions of the CSS are discussed by comparison with the results from the FEM and upper-bound approach.Some preliminary understanding of the instability mechanism of submarine slopes subjected to wave loading is achieved.The results show that the finite element result is close to the limit analysis result.The factor of safety oscillates with time under static water conditions and decreases gradually with increasing wave length and wave height.In addition,the FSof the submarine slope approach the hydrostatic FSas the water depth increases.This means that when the depth of water reaches a certain value,waves have no effect on the submarine slope.By analyzing the impact of the wave parameters on the CSS,increasing water depth is found to have no influence on the position of sliding surface,but the potential sliding surface position at different times changed significantly.