Time-dependent material behaviour of shotcrete – New empirical model for the strength development and basic experimental investigations

Abstract

In conventional tunnelling, the shotcrete lining is loaded at an early stage, so consideration of the time dependency of material properties during construction is vital. An important property of shotcrete concerning rock deformation is its early strength, which can influence the development of rock pressure and support resistance. The mechanical properties of the shotcrete change continuously during the hydration process. Material models exist to describe the mechanical behaviour, but these were mostly validated with dry shotcrete or older shotcrete mix designs. Continual improvements in admixture technology have improved the performance of shotcrete.Therefore, strength developments of a test series and practical projects are evaluated and a shotcrete test to determine the time-dependent material properties is carried out with a reference mix design. An empirical prediction model, which serves as a qualitative estimation of shotcrete strength processes, is designed based on the results of the evaluated strength developments. Based on the experimental investigations, a first basis for in-depth investigations of the time-dependent material behaviour of shotcrete is created.