Earthworms play an essential role in maintaining and restoring soil structure through burrowing. Although the importance of earthworms is well recognized, knowledge on penetration forces and energy requirements of burrowing remain limited. To investigate these mechanisms, we preformed measurements and simulations of cone penetration analogues, with cones that had a center hole to mimic soil ingestion by earthworms. Measurements were carried out to analyze soil displacement patterns for various cone characteristics, while discrete element method (DEM) simulations accelerated by graphical processor units (GPUs) were performed to quantify penetration forces and calculate energy requirements for burrowing. The influence of cone half-angle, the center hole diameter that mimic the mouth opening of an earthworm, and lubrication representing earthworm mucus are explored. The main findings show that more pointed cones reduce penetration force and compaction in the axial direction but limit soil ingestion, while blunter cones increase ingestion at the cost of higher penetration energy. Results indicate that cone half-angles of 25°-30° (given a 2mm center hole) maximize earthworm burrowing efficiency in the investigated silt loam soil, as in that case available energy from soil ingestion is five-fold the energy requirement of burrowing. Lubrication had little effect in a low organic content silt loam soil while it slightly reduced the required penetration force in a high organic content silt loam soil. Overall, the combination of experiments and DEM simulations offer a mechanistic understanding of soil ingestion of earthworms that was not previously available.