1527 This equipment enables rock indentation experiments under high-stress conditions. An indentation force is transmitted to the base through a drive rod. The base is designed with adapter sockets that allow for the replacement of inserts with different geometries, as shown in Figure 3. To investigate the influence of multiple inserts with different shapes on rock failure, spherical inserts and conical inserts, both with a diameter of 5 mm, were designed. Figure 3 - The structure of double-inserted tooth: a, spherical-spherical dual inserts; b, conicalconical dual inserts 2.2 3D Profilometer To accurately obtain the morphology of the fracture craters and differences in breakage angles, a KEYENCE VR-5000 series 3D profilometer was used in this study to scan the specimen surface, as shown in Figure 4. Figure 4 - KEYENCE VR-5000 series 3D profile scanner As shown in Figure 4, the entire scanning system consists of three parts: scanning software, a controller, and a stage. The stage can accommodate test specimens with a height below 75 mm and a weight less than 4.5 kg. The horizontal travel range of the X-Y axes is 184 × 88 mm, while the vertical travel range of the Z-axis is 73 mm. During the scanning process, the specimen is first placed on the stage, and autofocus is used to lock the scanning height before initiating the scan. During scanning, two telecentric lenses mounted on the top of the stage emit white LED beams, which are reflected off the object's surface and then captured by another telecentric lens equipped with a 1-inch, 4-megapixel monochrome CMOS sensor to form an image. Finally, the software resolves the 3D contour scanning results of the object's surface with a display resolution of 0.1 μm. 2.3 Experimental Materials The basic physical and mechanical parameters of the bluestone sandstone samples used in the experiments are presented in Table 1. Table 1 - Physical and mechanical parameters of experimental rock specimens Rock Type Density (kg/m3) Void Ratio (1) Elastic Modulus (GPa) Internal Friction Angle (°) Cohesion (MPa) Compressive Strength (MPa) Tensile Strength (MPa) Green Sandstone 2355.03 0.1464 16.52 46.54 9.75 65.35 4.85 Scanning Software Controller Specimen Stage High-Resolution CMOS Sensor
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