The RIDETHERISK project has made significant progress in both its scientific and methodological objectives, focusing on two core areas: understanding the fragmentation processes in rockfall events and developing a robust Quantitative Risk Assessment (QRA) framework for assessing rockfall-related risks in civil and industrial contexts.
In the initial phase at Politecnico di Torino (Polito), the project began with an extensive desk-based review of existing knowledge on rockfall fragmentation. This review has been continuously updated throughout the project to reflect new findings and evolving insights. Field inspections were conducted at selected open-pit mining and mountain sites in the Alpine region, where rock blocks of various lithologies were collected. These blocks were mechanically characterized through laboratory tests, and many samples were prepared for future drop tests to be conducted during the return phase. These tests aim to validate the fragmentation model currently under development.
During the 15-month outgoing phase at the University of Newcastle (UoN), the focus shifted to experimental work. The first 11 months were dedicated to designing and conducting laboratory tests, while the remaining period was used to analyse the results and develop a theoretical fragmentation model. Artificial samples replicating the mechanical behaviour of brittle rock were created and tested to simulate rockfall conditions. A comprehensive testing campaign was carried out, including drop tests and material characterization tests such as uniaxial compressive strength, Brazilian tensile strength, and toughness tests. Additionally, non-conventional indirect tensile tests were designed and performed to explore fracture modes under static loading and checking the compatibility with those observed under dynamic loads.
To investigate the influence of internal discontinuities on fragmentation, approximately 550 spherical samples with four different discontinuity configurations were prepared and tested. These included variations in the number, orientation, and position of discontinuities within the samples. The tests were conducted using a specialized fragmentation cell equipped with six high-speed cameras to capture pre- and post-impact behaviour. The impact velocity and angle of the discontinuities were varied to simulate different real-world conditions. In parallel, around 250 material characterization tests were performed to ensure consistency across all sample batches.
The second major experimental focus was on the influence of block shape. A total of 180 prismatic, cuboid, and slab-shaped samples were prepared and tested using both drop tests and indirect tensile tests. These tests aimed to assess how shape affects impact duration, number of contact points, post-impact trajectories, and fragmentation patterns.
All test data were processed using TEMA3D software to analyse fragmentation occurrence, fragment size distribution, and trajectory behaviour.
From these experiments, preliminary empirical and analytical models have been developed to predict fragmentation occurrence and characteristics. While these models have shown promising results, refinement is ongoing to improve their accuracy and reliability. In parallel, a physical-based trajectory model using a lumped-mass approach has been developed, along with a dedicated trajectory simulation code. Once the fragmentation module is fully validated, it will be integrated into this model to enable comprehensive rockfall propagation analysis.
In addition to the experimental and modelling work, significant progress has been made in developing the QRA framework. Although originally planned for the return phase, several components have already been completed. A QRA method for assessing social risk on road infrastructure has been developed, providing a framework for integrating fragmentation effects once the model is finalized. A preliminary method for evaluating economic impacts, specifically traffic delays, has also been conceived. In the context of open-pit mining, a quantitative hazard assessment framework for social risk has been established, with economic risk assessment planned for the return phase.
A first application of the QRA method for social risk, without the fragmentation module, has been carried out on a road infrastructure in the northwestern Alps. This pilot study provided a preliminary quantification of the risk to human life from rockfall events, demonstrating the method’s practical applicability and laying the groundwork for future, more comprehensive assessments.
The main achievements of the project to date thus include:
1) A large-scale experimental dataset on rockfall fragmentation, covering the effects of internal discontinuities and block shape.
2) Preliminary empirical and analytical models to predict fragmentation occurrence, fragment size, and post-impact trajectories.
3) A physical-based trajectory model and simulation code, ready for integration with the fragmentation module.
4) A QRA framework for assessing social risks from rockfalls on road infrastructures, and preliminar studies for assessing economic risks in road infrastructures and in mining contexts.
5) A pilot application of the QRA method in a real-world Alpine setting, demonstrating its potential for practical use.
These achievements represent a significant step forward in the scientific understanding and practical management of rockfall hazards. The integration of fragmentation dynamics into a comprehensive QRA framework will ultimately provide decision-makers with a powerful tool to assess and mitigate rockfall risks, supporting safer infrastructure, more resilient communities, and better-informed policy and investment decisions.
