Abstract: A rock sample fixing device with a three-jaw chuck for cyclic tension and compression testing including: a lower clamp and an upper clamp; the lower clamp including a lower connector connected to a loading base at a bottom of a testing machine, a lower end cap for fixing samples, a lower chain connecting the lower connector and the lower end cap, a first central position-limit mechanism, a second central position-limit mechanism, and a first hydraulic mechanism; the upper clamp including an upper connector connected to a loading base at a top of the testing machine, an upper end cap for fixing samples, an upper chain connecting the upper connector and the upper end cap, a third central position-limit mechanism, a fourth central position-limit mechanism, and a second hydraulic mechanism.

Abstract: A rock specimen, including a rock body having the shape of a cylinder or a regular square prism. The rock body includes: an upper end face, a first circular groove, a first cylinder, a first circular body, a lower end face, a second circular groove, a second cylinder, and a second circular body. The first circular groove is disposed on the upper end face of the rock body and has a circle center coinciding with the center of the upper end face of the rock body. The second circular groove is disposed on the lower end face of the rock body and has a circle center coinciding with the center of the lower end face of the rock body. The outer diameter of the first circular groove is smaller than the inner diameter of the second circular groove, and the first circular groove and the second circular groove are staggered.

Abstract: A rock specimen, including a rock body. The rock body includes: an upper part, an upper end face, a first circular groove, a first cylinder, a first circular body, a lower part, a lower end face, a second circular groove, a second cylinder, and a second circular body. The first circular groove is disposed on the upper end face of the rock body and has a circle center coinciding with a center of the upper end face. A method for testing pure shear of the rock specimen, includes: 1) disposing the rock specimen on a test bench of a rock mechanics testing system, allowing the end face of the second circular body to contact the test bench; and 2) operating the rock mechanics testing system, loading a pressure on the rock specimen via the end face of the first cylinder and the end face of the second circular body.