ABSTRACT
In many rock engineerings, such as drilling, blasting, earthquake, landslide, rockburst, oil-well fracturing, protection engineering of nuclear explosion etc.the rock materials are fractured under dynamic loading with widely varied loading rates. Therefore, it is very important to understand the relation between fracture toughness and loading rates. Some works have been done in this field. For examples, Costin [1] measured the dynamic fracture toughness of oil shale, but he did not get the relation between the fracture toughness and loading rates. Wu [2] and Liu [3] obtained the fracture toughness of granite, marble, tuff, and red sandstone, which showed an increasing tendency with loading rates. However, due to the limitation of their test equipments, the maximum loading rate in their tests was only 10 3 MPam 1 / 2 s - 1 . Employing SR spec imen suggested by ISRM for determining the fracture toughness of rock, Zhang et al [4,5] obtained the relation between loading rates and fracture toughness of marble. The maximum loading rate is about 1 x 10 7 MPam 1 / 2 s - 1 . This paper is a continuous and further study of [4,5], and the tested rock is gabbro at suburb of Beijing which is a typ ical igneous rock.
