立波作用下海床的有效应力与液化分析

Effective stress and liquefaction of seabed under the action of standing waves

波浪作用下海床的稳定性与液化分析是海底管线、防波堤和海洋平台设计中必须仔细考虑的问题 .本文推荐了一个循环荷载作用下土体的弹塑性实用本构模型 ,并给出了一种粉土的模型参数 .该模型直接根据初始应力状态和循环应力的大小与作用时间计算土体的塑性应变增量 ,在有限元计算中不需要引入弹塑性矩阵 .采用Biot理论和有限单元法 ,对海床有效应力的变化过程分析表明 ,波腹点下海床存在较大的液化可能性 .波浪作用对海床存在一定的压密作用 .

Stability and liquefaction are important to the design of offshore structures. A practical elastoplastic constitutive model for cohesionless soil under cyclic load is proposed. The parameters of the model for a kind of silt are obtained from un\|drained dynamic triaxial test. The plastic strain increment of soil under cyclic load can be calculated according to the initial stress states, magnitude of cyclic stress and duration. No elastoplastic matrix related to stress and strain is needed. Biot's consolidation equation is applied to the FEM computation program developed by the authors. Variation of effective stress of seabed response to standing waves indicates that the location of greatest potential liquefaction is in the area beneath the wave anti\|node. There is a densification effect to the seabed under the wave action.