Experimental study on controlled directional fracture blasting#br#
on PMMA mediums with flaws
YANG Renshu1，2，DING Chenxi1，YANG Liyun1，WANG Yanbing1，XU Peng1
(1. School of Mechanics and Civil Engineering，China University of Mining and Technology(Beijing)，Beijing 100083，China；
2. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and
Technology(Beijing)，Beijing 100083，China)
Abstract：The crack flaws and empty hole flaws were set in a single experiment using the experimental material of PMMA and the new system of digital laser dynamic caustics so that the effects of flaws on the crack propagation in the controlled directional fracture blasting were studied. The results show that the forms of flaws have little effect on the length of blasting induced main cracks. The propagation of main cracks have two stages. In stage I(0–120 μs)，the propagation velocity and stress intensity factor at crack tip decrease rapidly. In stage II(120 μs–crack arrest)，the effects on crack tips caused by stress wave reflected from flaws are more significant，the energy accumulation and stress concentration of crack tips are enhanced，and the velocity and dynamic stress intensity factor increase to a great extent. The peak velocity and peak dynamic stress intensity factor of blasting induced main crack decrease gradually with the curvature increasing of flaw sides during the stage II.
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2017, Vol. 36 
