Abstract: Failure to prepare the rockmass sample with joints of the same surface morphology as those of natural joints has long been infesting the mechanical experiment on the structural surfaces of rock mass. With the latest development of the 3D printing technique and the rapid surface scanning technique, a new method is developed for producing the joint specimens containing the joint surfaces similar to those of natural rockmass. In the proposed method, a 3D scanner is first used to obtain the point cloud data related to the surface topography of joints of natural rockmass; then the virtual specimen model containing natural joints and related surface morphology information is reconstructed, and finally the PLA mould with the joint surfaces is produced using the 3D printing technique. The shear specimens are prepared by pouring the similar material into the PLA mould. Three types of rockmass joint surfaces are copied with the proposed procedure; and a series of measurements and shear tests are conducted on the made joint specimens. The results indicate that: (1) the proposed method can copy accurately the joint morphology from the originally natural joint; (2) among the three types of rockmass joint specimens, the displacement-force curves of the specimens are very close to each other, showing that the consistency of the made specimens containing joint surfaces is satisfied under the identical conditions; (3) by comparing the joint surface contour before shearing to that after shearing, it is found that the shear-induced failure occurs heterogeneously.

Key words: 3D scanning, 3D printing, rock joint, shear experiment, backward preparation