An experimental study on the time-dependent behavior of crushable granular materials using 3D-printed particles

This paper aimed to investigate the potential capability of using 3D-printed particles to study the time-dependent behavior of a typical crushable granular material, i.e., rockfill. Different 3D printing techniques were compared, and gypsum powder and binder were chosen for printing crushable particles, which were found to have a comparable peak strength, ductility, and failure mode to those of the natural rockfill particles in the single-particle crushing tests. Then, large oedometer creep tests were performed on the two specimens of 3D-printed particles with and without predefined inner fissures and on a third specimen of natural limestone rockfill. The vertical pressures were applied in stages on each specimen, with a maximum value of 1.5 MPa. The test results showed that the patterns of creep strain development with time of the two specimens with 3D-printed particles were consistent with that observed for natural rockfill. The main modes of particle breakage for all three specimens after the test were asperity breakage and surface abrasion, while global fracture was not substantial. The predefined inner fissure in the 3D-printed particles only had a minor influence on the creep behavior of the specimen even at high vertical pressures. Compared with the limestone rockfill specimen, the specimens with 3D-printed particles showed similar creep behavior at low vertical pressures but exhibited much larger creep strain at high vertical pressures. The underlying mechanism of the observed phenomenon was explored.