Rock specimen and method for testing direct tensile strength of the same

A rock specimen, comprising a rock body having a shape of a cylinder or a regular square prism, the rock body comprising:

• 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;
• wherein
• the upper end face is in parallel with the lower end face;
• 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 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;
• an outer diameter of the first circular groove is smaller than an inner diameter of the second circular groove, and the first circular groove and the second circular groove are staggered;
• the first circular groove divides a first part of the rock body into the first cylinder located at the center and the first circular body surrounding the first cylinder;
• the second circular groove divides a second part of the rock body into the second cylinder located at the center and the second circular body surrounding the second cylinder;
• a diameter of the first cylinder is smaller than a diameter of the second cylinder;
• an end face of the first cylinder and an end face of the first circular body are disposed on a same plane;
• and an end face of the second cylinder and an end face of the second circular body are disposed on a same plane.