Experimental and numerical investigations of the mechanical behaviour of frozen granular soils

• Applicants: Dr.-Ing. Stylianos Chrisopoulos; Professor Dr.-Ing. Roberto Cudmani
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540426890

Artificial ground freezing (AGF) is an advanced, sustainable, and environmentally friendly construction technique that temporarily increases the subsoil's stiffness and strength and provides water tightness. It can be implemented effectively in urban conditions where the risk of using other subsoil improvement, water tightening, and dewatering techniques can be high due to complex or partially unknown boundary conditions and the consequences of damage. According to several studies in the literature, semi-analytical approaches based on the elasticity theory, some of them initially developed more than a century ago, and Finite Element Analysis (FEA) assuming elastic-ideal plastic material behaviour are still commonly applied to the design of AGF measures. However, shortcomings of these approaches often lead to inefficient designs since high safety factors are involved to counteract model simplifications and uncertainties. From a practical point of view, it is necessary to geotechnically and economically improve the design of AGF measures by means of advanced, user-friendly, and comprehensively validated constitutive models. Therefore, the overarching project goal is the experimental and numerical investigation of frozen granular soils under static monotonic and non-monotonic compressive as well as tensile loading. We will create a novel, unique and comprehensive experimental database for frozen sandy gravel and significantly extend an existing experimental database for frozen Karlsruhe medium sand. The use of both high-quality experimental databases and sophisticated data from the literature will result in a far-reaching enhancement, further development, and validation of the existing advanced constitutive model EVPFROZEN (elastic-viscoplastic frozen soil model). To achieve these ambitious goals, we propose the following specific sub-goals: (1.) Creating a novel mechanical experimental database for frozen gravel based on element tests at a uniform, constant temperature. (2.) Extending an existing mechanical experimental database for frozen Karlsruhe sand based on element tests at uniform, constant and time-varying temperatures. (3.) Creating a novel mechanical experimental database for frozen Karlsruhe sand based on model tests. (4.) Investigation, enhancement and further development of the existing constitutive model EVPFROZEN based on our own experimental database and data from the literature. (5.) Extensive EVPFROZEN model testing and validation based on our own experimental database and data from the literature.

• DFG Programme: Research Grants