Feasibility of Artificial Materials in Simulating Rock Failure Based on Rate-Dependent Brittleness Indexes

With the development of 3D printing and computer numerical control machining techniques, extremely complicated models physically simulating the underground structures in rock engineering were conducted. Whether these artificial materials can accurately simulate the cracking and failure modes of natural rocks should be studied. The present study uses an artificial material-moulded gypsum to compare with the mechanical behaviours of natural marble from the perspective of brittleness. The comparison can provide an insight into the feasibility of the physical simulation. In addition, to investigate the strain rate influence on brittleness with the background of dynamic loading related to rock engineering, the rate dependence of the brittleness is investigated considering the size effect. Six types of brittleness indexes proposed in the quasi-static loadings are studied under various loading rates with strain rates ranging from 10 –6 to 10 3 s −1 . The result indicates that not all the brittleness indexes are applicable in the dynamic regime. Two brittleness indexes are suggested to evaluate the dynamic gypsum brittleness due to its reasonable depiction of real dynamic brittleness. Gypsum is more brittle than marble under both quasi-static and dynamic loadings based on the analysis of brittleness indexes and cracking behaviour. Meanwhile, the experimental and numerical results confirm the influence of the brittleness of material on the cracking behaviours and imply that the artificial material should be assessed to ensure the validity and feasibility before the physical simulation of rock structures in engineering. Highlights The brittleness of 3D printing material in physical simulation should be considered. The dynamic brittleness of gypsum and marble is compared. The brittleness indexes are extended into the dynamic condition. Brittleness index can affect the cracking behaviour. The feasibility of 3D printing in rock mechanics should be evaluated before experiments.