GEOLAB - Transnational Access project M3ARBLE - Micro / Macro Modelling of Ageing Ballast: validation with Lab Experiments

The Micro - Macro Modelling of Ageing Ballast: validation with Lab Experiments project (M3ARBLE) was conceived to investigate the behavior of ballast at various stages of its service life. The project aims to characterize the mechanical behavior of ballast when it is new and after it has been subjected to numerous train passages and the effects of environmental conditions, which lead to degradation mechanisms such as abrasion, particle breakage, and pore structure contamination. By identifying the differences in the ballast behavior, the project seeks to select appropriate constitutive models and parameters for each degradation stage. These models, then, can be integrated into Finite Element (FE) numerical tools to predict vibrations at different points within the railway structure and surrounding ground.

To achieve this goal, M3ARBLE employs Discrete Element (DE) simulations of ballast samples under different conditions. These simulations replicate simple shear tests that encompass a range of loading rates and frequencies, reflecting the quasi-static and dynamic loads imposed by train passages. Calibration and validation of the DE model require experimental data, for which the large-scale triaxial apparatus at the Slovenian National Building and Civil Engineering Institute (ZAG) has been utilized as part of the GeoLab project.

This document outlines the experimental procedures and presents preliminary results from two cyclic simple shear tests conducted on different ballast samples using the largescale triaxial apparatus from ZAG.