A new method to evaluate the mechanical behaviour of granular material with large particles: theory and validation

Because of the lack of experimental devices for testing granular materials with large particles, the mechanical behaviour of rockfills is not very well known. This lack of knowledge can lead to improper design of rockfills dams, and as a consequence, to severe accidents including dam failures. A new method has been developed for evaluating the mechanical behaviour of rockfills based on the estimation of size effect in granular materials, affected by grain breakage. The size effect, resulting from Fracture Mechanics, can be expressed by the fact that the strength of individual particles decreases when their size increases. The aim of this new method is to determine the mechanical properties of an assembly made of large particles (grain size distribution G1) from the measured properties of a granular assembly made of smaller particles (grain size distribution G0), of the same mineral stock, taking into account the different breakage capacity of particles of different sizes. G0 and G1 should have parallel grain size distributions. Some triaxial and crushing tests were performed on granular assemblies made of homogeneous limestone particles with two parallel grain size distributions. Comparison between experimental results and numerical predictions shows that this method can estimate with good accuracy the strength of granular materials made of large particles