Experimental Study of the Effect of Length and Angle of Cross-Cracks on Tensile Strength of Rock-Like Material

Discontinuities are an integral part of the rock masses, and fewer rocks are found in nature which are intact. These discontinuities control mechanical properties of rocks, and lack of attention to their growth and interaction results in reduced rock structure's useful lifespan. The research to date has tended to focus on single cracks rather than crossover cracks. In recent years, there has been an increasing interest in V shaped cracks. In this study, initiation and propagation of V-shaped cracks, the nature of the cracks, failure mode, and failure stress in the specimen of Brazilian disks on a rock-like material was experimentally investigated. The cracks were studied in this study are the open type with the thickness of 1 mm and created by thin steel shims shaped as V, with five different angles. Fifteen different types of crack geometries, with different angles and length, have been investigated in specimens of Brazilian disks with 100 mm diameter and 30 mm thickness performing 45 Brazilian tests. The variables that have been considered are the angle between the two cracks and the length of each crack. With the results of Brazilian tests, it was observed that the predominant mode of failure in the V-shaped cracks is tensile. It also showed that the effect of crack length on the fracture process from the angle between the two cracks is much higher. Another important finding was that the angle of 45 degrees reaches failure in minimum tension, so this angle is critical. In some specimens, one tip from three tips of V-shaped crack remains inactive which appears to be the asymmetric failure pattern in intact Brazilian disks. A possible explanation for this might be that stress distribution in the sample, and the possible existence of the low difference between lengths of these two cracks may be responsible for this phenomenon.

Automated summary

This study experimentally investigated the initiation and propagation of V-shaped cracks in rock-like material, showing that the dominant mode of failure in V-shaped cracks is tensile. It was also observed that the angle of 45 degrees reaches failure in minimum tension, making it critical in the failure process.