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Abstract Rockburst test of Laizhou granite is carried out under true triaxial experimental machine system with one surface of the sample unloading suddenly，and the rockburst fragments are collected. The rockburst fragments are measured including the mass，length，width and the thickness. The fragment quantities of coarse，medium，fine and micro grains in different size ranges，quality and particles distribution are analyzed also. Rockburst fragment fractal of the granite is obtained according to the relations of the fragment length，width，and thickness to cumulative number. Respectively，the relation of ratio of cumulative mass of equal length which is smaller than it divided by the total mass to equal length，as well as the relation of equal length to cumulative number of fragments. The results show that the degree of crushing of granite rockburst fragments is higher and with obvious slab characteristics. The micro-particles(approximately＜0.075 mm of rock sample after rockburst are analyzed by laser-particle machine. The most，moderate and smallest micro-particles mass of rock sample after failure is generated under rockburst test，true triaxial uniaxial compression test condition，respectively. The characteristics of particles distribution curves appear that it is gradual of rockburst test，steep of both true triaxial compression test and uniaxial compression test. Most micro-particles diameters of rockburst failure are smaller than of others. The particle diameter corresponding to the largest volume percentage value in the micro-particles distribution curves of rockburst are 40 and 60 μm. The particle diameters of true triaxial compression and uniaxial compression test are 80 and 100 μm respectively. The fractal dimension of micro-particles is calculated with the diameter-volume distribution. It implied that the micro-particles of rockburst failure fits the physics concept of statistics self-similar fractal rules，the others are not. More energy is dissipated during rockburst than that of true triaxial and uniaxial compression since a lot of micro-particles generated for rockburst sample.
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Received: 14 January 2009
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