This paper provides an overview of the work of the Australian Research Council-funded Centre for Geotechnical Science and Engineering on free falling projectiles that have applications as seabed characterisation tools and as anchoring systems for floating facilities. These projectiles are released in water and dynamically embed into the seabed through the kinetic energy they gain during freefall. The high penetration velocity, which can be up to 25 m/s at impact with the seabed, induces shear strain rates in the soil that are up to eight orders of magnitude higher than in a typical laboratory test. The difficulty in quantifying the soil strength at these very high strain rates, together with hydrodynamic aspects including pressure drag and potential water entrainment along the projectile-soil interface, complicates assessment of the penetration response. A large database of centrifuge and field data has been collated by the Centre and is used in this paper to quantify embedment potential and to examine the merit of a simple analytical framework that captures the dynamic response of free-falling projectiles. Aspects of the dynamic embedment process that cannot be predicted by the analytical framework, including potential hole closure during installation and pore pressure generation are investigated in finite element analyses that model the dynamic penetration of projectiles in soil. Example results from these analyses are provided.
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机译：本文概述了澳大利亚研究委员会资助的岩土科学与工程中心在自由落体射弹方面的工作，这些射弹可作为海床表征工具和浮动设施的锚固系统应用。这些弹丸在水中释放，并通过它们在自由落体过程中获得的动能动态地嵌入海床中。与海床相撞时的高穿透速度可高达25 m / s，它在土壤中引起的剪切应变率比典型的实验室测试高出八个数量级。在如此高的应变速率下，难以量化土壤强度，以及流体动力学方面的问题，包括沿弹丸-土壤界面的压力阻力和潜在的水夹带，使渗透反应的评估变得复杂。该中心已经整理了一个大型的离心机和实地数据数据库，并在本文中用于量化嵌入潜力并检查可捕获自由下落弹丸动态响应的简单分析框架的优点。分析框架无法预测的动态嵌入过程的各个方面，包括在安装过程中可能发生的孔封闭和孔隙压力生成等问题，都通过对射弹在土壤中动态渗透的有限元分析进行了研究。提供了这些分析的示例结果。
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