Abstract: Under two modes of hole sequential and row sequential detonation， the influence of borehole dense coefficient on blasting fragment and damage degree is numerically simulated. In the simulation process， the dense coefficient was improved from 1.00 to 1.92， and the average crushing size d50， ultimate crushing size d90 and bulk ratio Br were taken as evaluation index of blasting fragment， and system rupture degree Fr was taken as evaluation index of damage degree respectively. The numerical simulation results showed that under the mode of hole sequential detonation， the influence of borehole dense coefficient was not obvious as each hole had two free surfaces. However， under the row sequential detonation， the breakage of rock was more uniform along with the density coefficient increasing， and more blocks appeared in the rectangular region surrounded by the holes along with the density coefficient lowered. The lower the density factor is， the larger the distribution of the bulk is. Therefore， under the mode of row sequential detonation， blasting effect can be obviously improved by properly increasing the hole space and shortening the row distance.

Key words: Numerical simulation, Dense coefficient, Block size, Damage degree