Our research tackles this by focusing on something subtle: how individual particles actually deform, or 'squish,' even a tiny bit. We've created a new computer model that simulates how these particles interact. Unlike older models that assumed particles were perfectly rigid, ours shows that even minimal squishing creates 'compression chains'—lines of deforming particles that dramatically change how force and motion travel through the material.

This simple, grain-scale deformation helps explain big-picture phenomena. For instance, it clarifies why thin layers of granular material behave differently than thick ones, a puzzle known as 'thin layer stability.' Our model also revealed surprising patterns in how forces are transmitted in uniform materials and, importantly, how mixing different sizes or stiffnesses of particles profoundly affects how quickly forces (like sound waves) travel through them.

Our model is publically available within the Julia ecosystem under the DeformableGrains.jl package.