The researchers conducted compression tests on rocks to understand how spalling occurs. They found that spalling can happen in two ways: one from cracks at flaw tips, and the other from mixed wing and secondary cracks. The size of spalling is usually larger in the second type. Spalling is more likely to happen with a smaller inclination angle and more flaws. When spalling occurs, the specimen fails quickly. They also introduced a ratio (k) to determine when a material loses its support, which is important for materials and structures in engineering.