海洋结构性粘土的循环软化效应及其微观机理研究

Focusing on the key mechanical problem of marine structured clay’s cyclic softening, a series of dynamic hollow cylindrical torsional shear tests are carried out under K0 consolidation condition with changing on different factors such as cyclic stress ratios, frequencies and overconsolidation ratios. Dynamic strength index and its variation are obtained under wave loads. Utilizing scanning electron microscopy and image analysis technique, the microscopic structure characteristics of marine structured clay are quantitative analyzed in the progress of consolidation and cyclic loading. A characteristic parameter which can comprehensive reflect the marine clay microscopic structures is determined using fractal theory. The quantitative relationship between microscopic structure characteristic parameter and mechanical properties is then built. And then, the dynamic strength softening of marine structured clay under cyclic loading is described by the index of cyclic softening. Basing on the impact and contribution of the microscopic structure characteristic parameter and other factors to the index of cyclic softening, the marine structured clay cyclic softening model is established which can reasonable consider the impact of marine structure. Appropriate numerical method is developed and numerical simulation results and experimental results are verified. This research will provide a theoretical and application basis for the cyclic softening of marine structure clay and a technical support for the marine geotechnical practices.

针对海洋结构性粘土的循环软化这一关键技术问题，开展一系列原状海洋结构性粘土在K0固结条件下，不同循环应力比、不同循环荷载频率以及不同超固结比的动态空心圆柱扭剪试验，获得波浪荷载作用下动强度指标及其变化规律。运用SEM扫描电镜和图像分析技术，对海洋结构性粘土固结和循环加载过程中土体微观结构变化特征进行定量分析。运用分形理论，确定一个能综合反映土体微观结构的特征参量，构建微观结构特征参量与宏观力学性质的定量关系。在此基础上，采用循环软化指数来描述海洋结构性粘土在循环荷载作用下动强度的软化程度，基于微观结构特征参量和荷载因素等对循环软化指数的影响和贡献，建立一个可合理考虑微观结构影响的海洋结构性粘土循环软化模型。开发相应的数值计算方法，并将数值模拟结果与试验结果对比验证。为揭示海洋结构性粘土循环软化效应提供理论与应用基础，为海洋岩土工程实践提供相应的技术支持。

针对海洋结构性粘土的循环软化这一关键技术问题，开展一系列原状海洋结构性粘土在K0固结条件下，不同循环应力比、不同循环荷载频率以及不同超固结比的动态空心圆柱扭剪试验，获得波浪荷载作用下动剪切模量及其变化规律。运用SEM扫描电镜和IPP图像分析软件，对海洋结构性粘土固结和循环加载过程中土体微观结构变化特征进行定量分析。运用分形理论，确定周长-面积分形维度值和孔隙分形维度值反映土体微观结构的特征参量，构建微观结构特征参量与宏观动剪切模量的定量关系。在此基础上，采用循环软化指数来描述海洋结构性粘土在循环荷载作用下动强度的软化程度，基于微观结构特征参量对循环软化指数的影响和贡献，建立一个可合理考虑微观结构影响的海洋结构性粘土循环软化模型。为揭示海洋结构性粘土循环软化效应提供理论与应用基础，为海洋岩土工程实践提供相应的技术支持。