Abstract: In order to control the quality and stability of high bench parallel blasting slopes,based on traditional presplitting blasting technique,a semi spaced hole guided pre-splitting blasting technique was proposed. The stress distribution law and crack expansion of the separated hole guided pre-splitting blasting were analyzed. The study results show that the semi spaced hole played a guiding role in the upper unfilled section of the empty hole,forming tensile stress concentration,and strengthening the charging section at the bottom of the blast hole to form compressive stress concentration,make up for the insufficient charging of normal holes and overcome the deep clamping effect of blast holes. Four schemes were selected for semi spaced hole charging,namely 1. 5,2. 0,2. 5,3 kg,and hole spacing of 0. 6,0. 7,0. 8,and 0. 9 m. Numerical analysis and onsite experiments were conducted on the semi spaced hole technology scheme. The results indicated that when the charging amount was 2. 5 kg and the linear charging density was 0. 42 kg / m,the hole spacing was selected as 0. 8 m,which maximized energy utilization and ensured the penetration of the bottom blast hole. The study have a certain reference significance for the practice of boundary blasting in open-pit mining.

Key words: mine blasting,high step parallel section,presplitting,half spacing hole guide,clamping effect