Artificial ground freezing applications using an advanced elastic-viscoplastic model for frozen granular soils

Despite its increasing use and ongoing technical advance, artificial ground freezing (AGF) is still considered an expensive technique compared to conventional construction methods. The main reason for this is a conservative AGF design, which results from (semi-)analytical and elastic approaches that oversimplify the complex mechanical behavior of frozen soils. In contrast, advanced constitutive models for frozen soils offer a unique opportunity for efficient optimization of the AGF design. For this purpose, they must be implemented in finite element analysis (FEA) codes, extensively tested, and validated for AGF boundary value problems. This study presents the testing of a recently proposed elastic-viscoplastic model for frozen granular soils in both a shear and creep failure boundary value problem. The model can capture the rate-dependent ultimate shear strength for different temperatures observed in shear failure experiments from the literature. The simulation of a conventional tunnel excavation supported by a frozen soil body reflects the model's capability to accurately reproduce the frozen soil deformations experimentally measured during the excavation and the following creep phase. In addition, the tunnel boundary value problem is also simulated with an enhanced elastic model for frozen soils. Here, the comparison of both model responses highlights the geotechnical, economic, and safety AGF design potential of the proposed advanced model in relation to the simplified approaches commonly used hitherto.