Method for measuring rock I-type fracture toughness based on critical distance theory

The invention discloses a method for measuring rock I-type fracture toughness based on a critical distance theory. The method comprises the following steps: S1, manufacturing rock beam standard test pieces with different grooving widths; s2, carrying out a three-point bending test on the rock beam test pieces with different cutting groove widths on a rock uniaxial compression testing machine, and recording a cutting groove opening P-V curve; s3, determining the load during crack initiation according to the P-V curve; s4, according to the crack initiation load and the corresponding cutting groove opening displacement, the characterization fracture toughness of the rock under different cutting groove widths is calculated; s5, drawing a curve representing the change of the fracture toughness along with the square root of the width of the cutting groove, and performing function fitting on the curve; and S6, according to a relational expression between the inherent fracture toughness of the rock and the characteri