Abstract: In order to analyze the influence of the blasting dynamic load on defects extension of roadway surrounding rock in different locations, the explosion load system using dynamic reflected caustics has been used to conduct the organic glass model experimental study. The experimental results have shown that under the influence of dynamic load the vertical crack at the top of the roadway is easier to extend than others, then are the inclined cracks at the arch and the corner，and the last ones are the horizontal cracks with the data of cracks propagation length of 31，17，20 and 6 mm respectively. The value of the displacement of crack propagation has a direct relationship with the value of the stress intensity factor and we can see that the value of the stress intensity factor of the vertical crack at the top of the roadway is greater than that of other three cracks, then is the value of the inclined cracks at the arch and corner and the value of the horizontal crack is at the minimum level. The above research results have positive influence on reducing the disturbance and damage of the blasting dynamic load on surrounding rock, and on saving the cost of surrounding rock supporting, ensuring construction safely and rapidly.

Key words: the blasting dynamic load, crack propagation, dynamic caustics system, stress intensity factor