循环荷载作用下海洋软黏土软化特性及锚板基础承载力研究

Suction Embedded PLate Anchors (SEPLA), which have been recently used as anti-uplifting foundations for deep sea platforms and large floating structures, have adventages such as low costs and relatively accurate anchoring point. Most existing researches on the bearing capacity of plate anchors are limited to static analyses. The effect of offshore dynamic/cyclic loading on the bearing capacity of plate anchors are not very clear. In this study, the dynamic softening behaviour of soft clay under cyclic tension, compresion and shear loadings, and under full flow shearing will be investigated by dynamic triaxial, torsional shear tests on clay samples and by T-bar, plate and ball penetration tests on clay models. The relationship of the results from various tests will be discussed. A quantitative model to calculate the equivalent cyclic shear strength of clay will be presented. 1g and centrifuge tests will be carried out to study the dynamic bearing resistances of plate anchors. The machanisms of how dynamic loading affects the anchor bearing capacity will be investigated by the soil flow mechanisms captured by Partical Images Velocimetry (PIV) technology, and by the distribution and variation of pore water pressure above and beneath the plate anchor. Large deformation finite element (LDFE) programs, in which the dynamic softening behaviour of clay is considered, will be developed. Then a large amount of cases of cyclic uplifting/penetrating processes of plate anchors and various penetrometers will be simuated by the LDFE method. Efforts will be paid on correlating the bearing capacity of plate anchors to the resistance of penetrometers under cyclic loading. This study has great theoretical and practical significances in dynamic softening behaviour of soft clay and in bearing capacity design of plate anchors.

吸力埋置锚板（SEPLA）作为深海平台和大型浮式结构的一种锚固基础，具有造价低、定位准确等优点。目前锚板承载力的研究多为静力分析，海洋环境动力荷载的影响尚有待进一步研究。本项目拟采用动三轴、动扭剪材料试验及T-bar、盘形和球形触探仪模型试验，分析黏土在拉、压、剪切及完全流动机制等循环应变模式下的软化特性，分析不同手段测试结果的关联性，建立黏土等效循环强度定量计算模型；采用常规重力和离心机模型试验，研究循环荷载作用下锚板基础的承载力特性；采用PIV图像识别技术分析土体流动机制，采用孔压传感器测量锚板前后孔压分布和变化规律，进而分析循环荷载对锚板承载力的影响机理；开发考虑黏土动力软化特性的大变形有限元方法，计算锚板和触探仪的循环拉压过程，建立锚板承载力和触探仪反力之间的量化对应关系。本项目在黏土动力软化特性和锚板承载力设计方面具有重要理论意义和工程应用价值。

吸力埋置锚板（SEPLA）作为深海平台和大型浮式结构的一种锚固基础，具有造价低、定位准确等优点。目前锚板承载力的研究多为静力分析，海洋环境动力荷载的影响尚有待进一步研究。本项目进行了动三轴试验及T-bar、盘形和锥形触探仪模型试验，分析了黏土在循环触探试验下的强度软化特性，分析了不同手段测试结果的关联性，确立了黏土等效循环强度定量计算模型及其参数确定方法；进行了常规重力和离心机模型试验，研究了循环荷载作用下锚板基础的承载力特性，分析了应力水平的影响；开发了PIV图像识别技术分析试验过程中土体的流动机制，结合有限元计算，分析了循环荷载作用下黏土强度应变软化对锚板承载力的影响机理；开发了考虑黏土应变软化特性的大变形有限元方法，计算了锚板和触探仪的循环拉压过程，建立了锚板承载力和触探仪反力之间的量化对应关系，提出了考虑黏土强度应变软化的锚板承载力设计计算方法。本项目在黏土应变软化特性和锚板承载力设计方面具有一定理论意义和工程应用价值。