Experimental study on the size effect and anisotropy in mechanical properties of fractured rock mass based on 3D printing

The size effect and anisotropy of fractured rock mass mechanical parameters are difficult problems to solve in the field of engineering. This study taken full advantage of sand 3D printing technology to batch-reproduce complex structures and prepare rock-like specimens with different sizes and rotation directions. The size effect and anisotropy of the fractured rock mass were investigated. Digital image correlation was used to conduct noncontact full-field observations of the specimen. The results showed that the sand 3D printing specimens have the advantages of high precision and brittleness and can reproduce the deformations and failure processes of natural rock. The compressive strength and failure mode of the fractured rock have significant size effect characteristics. Assessing the size effect on the compressive strength of the specimen, 100 x 100 mm is the mechanical representative elementary volume (mREV) scale. The compressive strength and failure mode of the fractured rock under the mREV scale show obvious anisotropy. Based on the size effect of fracture density, 80 x 80 mm was identified as the geometric representative elementary volume (gREV) scale. The gREV scale was smaller than and close to the mREV scale was found. In addition, the differentiation rate of standard deviation (DRSD) is defined to provide information on the dispersion of the strain field and the precursor information of crack initiation during the deformation and fracture of the rock mass. This study provides a new method for laboratory experimental studies on the size effect and anisotropy of complex fractured rock masses from the perspective of 3D printing.