1 Overview and main features
tapio-K is a code written in C for 2D or 3D DEM simulations. Newton’s second law is integrated by means of the velocity Verlet algorithm for spherical bodies. Boundary conditions focus on common geomechanical devices (Casagrande/Jenike shear cell, triaxial cell with membrane, 3-axis cell with 6 rigid walls, oedometer) but also on (e.g.) silo with trapdoor, mono-periodic conditions for tracked vehicle or granular ﬂows. In addition to common contact laws (linear/Hertz-Mindlin contact and Coulomb friction), the code includes various cohesion force-laws. In particular, the capillary cohesion due to the combined action of surface tension and suction operates in diﬀerent formulations. Since the spatial distribution of the capillary bonds mainly governs the strength, several (empirical) models are implemented.