南海北部陆坡软黏土动力应变-孔压特性试验

针对南海北部陆坡原状软黏土，开展了不同偏压固结比 和循环应力比CSR条件下的动三轴试验，探究了动荷载作用下试样的残余动应变、残余动孔压与循环振次的变化规律；综合考虑试验过程中残余动应变和残余动孔压的关联性，提出了基于动应变-孔压模式的动三轴试验破坏标准，并采用微观电镜扫描（SEM）图像揭示其作用机制。研究表明：在给定 条件下，CSR值不同，残余动应变随循环振次的发展趋势呈现出显著差异性，而残余动孔压随循环振次的变化规律基本一致；随着 的增加，CSR临界值逐步增大，相应的最终残余动应变逐渐减小，而残余动应变-动孔压曲线也表现出相似特征；将传统的应变值破坏标准扩展至由应变-孔压曲线拐点控制的破坏区间，可以有效界定破坏振次并描述试样的完整破坏过程，揭示动荷载条件下试样内在的有效应力-应变-孔压互馈机制。上述研究成果将为南海北部陆坡软黏土软化-孔压模型的建立、海洋地质灾害评价与预测、海洋工程基础设计提供可靠参考。

Experiment on dynamic strain-pore pressure of soft clay in the northern slope of South China Sea

Referring to the original soft clay in the northern slope of South China Sea, the dynamic triaxial tests were carried out under different conditions of consolidation ratio and cyclic stress ratio CSR. The development rule of the residual dynamic strain, residual pore water pressure and the relationship between them were discussed. Considering the correlation between residual strain and residual pore pressure in the test process, the failure standard of dynamic triaxial test based on strain-pore pressure mode was proposed. The mechanism of mutual feed and its interaction mechanism were revealed by the scanning electron microscopy (SEM) technique. The research results indicate that under the condition of designated and different CSR, the development trends of the residual dynamic strain and cyclic vibration frequency curves show a significant difference, while the change laws of the residual dynamic pore pressure and cyclic vibration frequency curve are basically the same. With the increase of , the critical value of CSR gradually increases, while the final residual dynamic strain gradually decreases. The similar characteristics of changing law can also be found from the curve representing the relationship between residual dynamic strain and residual pore pressure. Furthermore, the conventional failure standard based on strain value is extended to the failure region controlled by the inflection point of the strain-pore pressure curve, which can effectively define the failure vibration frequency and completely describe the whole failure process of the specimen, even reveal the inherent mutual feedback mechanism among effective stress, strain and pore pressure. Research results from this study can provide reliable reference for the establishment of dynamic softening model in soft clay, the evaluation and prediction of marine geological hazards, and the foundation design of ocean engineering in the northern slope of South China Sea.