Experimental investigation and development of a theoretical model for the vibrofluidisation of dry granular materials

干燥颗粒材料振动流化理论模型的实验研究和开发

• 批准号: 461480840
• 负责人: Professor Dr.-Ing. Frank Rackwitz
• 金额: --
• 依托单位: Fachgebiet Grundbau und Bodenmechanik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/461480840?language=en
• 关键词: Experimental; investigation; development; theoretical; model

The aim of the proposed research project is the development of a theoretical model for describing the vibrofluidisation of dry granular materials like sand, based on the results of geotechnical laboratory tests. This theoretical model is then supposed to be transferred into a material model suitable for implementation into a finite element program in order to solve later complex geotechnical boundary value problems.In this context, vibrofluidisation means the emergence of fluid-like properties within a granular material subject to vibrations with large acceleration amplitudes. Fluid-like properties are, for example, a reduced shear strength or complete lack thereof, viscous stress components and hydrostatic stress states or the evolution of convective motions. Although the existence of this phenomenon has long been known in the world of geotechnical engineering, only few studies and incomplete approaches toward it’s explanation exist. Since recent findings suggest the relevance vibrofluidisation has for construction techniques like vibratory pile driving and vibrocompaction, a need for further research can clearly be stated. The research project focusses on the deformation behavior and shear strength reduction of granular materials, while being subjected to vibrations. The latter is attributed to the emergence of a collisional stress caused by oscillating grains, the reduction of effective stresses due to inertial forces and the reduction of mobilized friction due to steady grain movements.The experimental work will consist of oedometric tests for investigating the compactive behavior, as well as triaxial tests for investigating the shear strength during vibration. For this purpose, conventional cells will be mounted on shaking tables and modified, so that the loading can be applied pneumatically. Model tests simulating the settlements of a foundation on sand under vibrations will be performed as a means of validating the material model.Developing this material model will be the subject of the theoretical work, as well as the implementation into a finite element program and the validation with the results of the executed laboratory tests.

拟议研究项目的目的是根据岩土实验室测试的结果，开发一个用于描述沙子等干燥颗粒材料振动流化的理论模型，然后将该理论模型转化为适合实施的材料模型。到有限元程序中，以便解决以后复杂的岩土边值问题。在这种情况下，振动流化意味着在受到大加速度振幅振动的颗粒材料中出现类流体特性。例如，剪切强度降低或完全缺乏、粘性应力分量和静水应力状态或对流运动的演变虽然这种现象的存在在岩土工程领域早已为人所知，但研究很少且不完整。由于最近的研究结果表明振动流化与振动打桩和振动压实等施工技术相关，因此可以清楚地表明需要进一步研究该研究项目的重点是变形行为。颗粒材料在受到振动时剪切强度降低，后者归因于振荡颗粒引起的碰撞应力的出现、惯性力导致的有效应力的减少以及颗粒稳定运动导致的移动摩擦的减少。实验工作将包括用于研究压实行为的体积测试，以及用于研究振动过程中剪切强度的三轴测试。为此，传统的单元将安装在振动台上并进行修改，以便可以施加载荷。将进行气动模型测试，模拟振动下沙子上的基础沉降，作为验证材料模型的一种手段。开发该材料模型将是理论工作的主题，以及在有限元程序中的实现。对所执行的实验室测试结果进行验证。