Abstract
In order to effectively reduce the disturbance of the precrack blasting vibration on slope rock mass, except paying attention to the damping effect of the precrack, it is also necessary to optimize the blasting parameters and initiation mode of the precrack itself. Based on the blasting theory and empirical formula, the parameters of presplitting blasting such as the hole diameter, hole spacing, charge decoupling coefficient, and line charge density were determined, and field tests of conventional pre-splitting blasting and presplitting blasting with precise delay and hole-by-hole initiation were carried out on the west slope of Buzhaoba. Regression analysis was carried out on the vibration monitoring data, and the blasting vibration attenuation regularity of slope particles was obtained. By comparing the monitored vibration velocity of the two presplitting blasting tests and the forecast results of theoretical calculation, the average reduction rate of the conventional same row blasting vibration is 26.40%, while that of the hole-by-hole blasting vibration can reach 41.45% with a half hole rate of 80.7% and an irregularity of about 130 mm. Results show that the effect of precise delay initiation between preholes based on the digital electronic detonator is better than that of the simultaneous initiation of preholes. Therefore, it is suggested that the hole-by-hole presplitting blasting technology should be applied in the excavation of boundary slope and the treatment of high and steep slope.
Highlights
Buzhaoba open-pit coal mine, which belongs to the Xiaolongtan Mining Bureau in Kaiyuan City of Yunnan Province, is the main operating mine crater
Based on the field test of high and steep slope mining in open-pit mine, this paper analyzed the difference between the traditional presplitting blasting and precracking holeby-hole initiation blasting technology, and the following results are obtained: (1) The calculation method for determining presplitting blasting parameters is summarized, and the parameters of presplitting blasting in the studied experiment site are determined as follows: hole diameter is 100 mm; cartridge diameter is 32 mm; hole spacing is 0.8 m; charge density is 450 g/m; filling length is 1.0 m; and delay time between hole-by-hole is 12 ms
(2) The precise time-delay hole-by-hole initiation technology based on digital electronic detonator meets the requirements of presplitting blasting
Summary
Buzhaoba open-pit coal mine, which belongs to the Xiaolongtan Mining Bureau in Kaiyuan City of Yunnan Province, is the main operating mine crater. On one hand, presplitting blasting can prevent the spread of explosion stress wave to the reserved rock mass by way of forming cracks with a certain width and depth between the main area and the reserved zone, so as to reduce or even cut off the blasting. Yang et al [11] obtained the deformation characteristics and failure mechanism of DHPB through numerical simulation and model test of specimens under horizontal compressive stress, compressive vertical stress, and noncompressive stress, as well as morphological analysis of presplitting cracks after presplitting blasting. LS-DYNA was used to establish the deep hole presplitting blasting model, and the crack evolution law and the attenuation characteristics of peak particle velocity of rock under the synergistic effect of blasting stress wave and detonation gas were analyzed to verify the rationality of blasting parameters. In view of the stability control requirements of west slope cutting and load reduction in the open-pit mine, it is urgent to optimize the conventional presplitting blasting control scheme to further reduce the harmful effect of vibration
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