|
Abstract Brittleness is one of the most important mechanical properties of rock. The fragmentation efficiency of rock is closely related to the rock brittleness. No unified brittleness index of rock is confirmed in evaluating rock fragmentation efficiency by disc cutter. The existing 35 different brittleness indices were summarized and classified into seven categories with respect to strength，strain，strain energy，hardness，Mohr envelope，special tests，etc. In order to study the relations between the rock brittleness and the rock fragmentation efficiency by disc cutter，the normalized specific energy concept was introduced after carrying out the indentation tests with disc cutter，and a new index of rock brittleness was proposed. In addition，the relations between the normalized specific energy and brittleness indexes based on strength and indentation test were mainly studied. The results show that it is more difficult to penetrate into the rock of high strength for disc cutter. The relationships between the normalized specific energy and brittleness indexes B2 and B4 were found to be exponential. With the increasing of brittleness indexes B2 and B4，the normalized specific energy decreased but the rock fragmentation efficiency increased. Therefore，the brittleness index B2 can be firstly used for evaluating the rock fragmentation efficiency，followed with the brittleness index B4. The uniaxial compressive strength of about 20 MPa can be defined as the transitional uniaxial compressive strength，and disc cutter may be not suitable for cutting the soft rock with uniaxial compressive strength less than 20 MPa.
|
|
|
|
|
|
2016, Vol. 35 
