Experimental study of the formation process and behaviors of spalling in rock materials

To study the mechanism and behavior of spalling in rocks, a series of compression tests are conducted. The results show that in compression tests two types of spalling can be observed, and type one is produced by secondary cracks initiated at the tips of flaw, and type two is produced by mixed wing and secondary cracks, and the spalling area of type two is usually bigger than that of type one. In addition, the formation process of spalling can be influenced by the inclination angle and the number of flaw. When the inclination angle ranges from 60 degrees to 90 degrees, spalling is difficult to occur and has the increasing trend with the increase of flaw number. A relative smaller inclination angle is propitious to induce the occurrence of spalling. Spalling is possibly regarded as an indication of specimen failure, once spalling occurs, failure of the specimen quickly ends. Furthermore, a ratio (k) is proposed and discussed, according to the value of k, we can judge when a material or structure completely loses its support or bearing capacity, and this ratio (k) is also of great significance for mechanics of materials and structures, as well as practical engineering.