摘要
针对宽孔距爆破破岩技术中炮孔密集系数合理取值的问题,在总结国内外宽孔距爆破破岩机理的基础上,开展了炮孔密集系数为1.7、2.5、3.5、4.5的有机玻璃板室内爆破试验,并基于常规态型近场动力学原理,开发了爆破计算模块,对宽孔距爆破破岩中裂纹扩展过程、介质位移响应规律进行了研究.结果表明:临空面一侧的径向裂纹受到临空面反射拉伸应力波的作用,表现出向临空面拐角分叉的特征,并逐渐向临空面扩展,最后形成主裂纹组成漏斗形状.在最小抵抗线固定不变条件下,随着炮孔密集系数的增加,应力降低区逐渐增大,同排炮孔间的径向贯通裂隙消失,过大的炮孔密集系数也进一步造成前后排孔间贯通裂纹消失,最后导致单孔爆破的情况发生.位移计算结果进一步证实了上述规律,并且当炮孔密集系数较小时,前排炮孔留下的岩埂刚好被后排炮孔爆破破碎,随着炮孔密集系数的增大,后排孔爆破对前排炮孔所留下的岩埂破碎作用效果逐渐降低.建议实际工程中根据岩体力学性质、地质条件以及爆破目的适当调整密集系数来降低炸药单耗与大块率.
Abstract
Aiming at the problem of reasonable spacing-burden ratio in wide hole spacing blasting technology,la-boratory blasting experiments of PMMA plates with the spacing-burden ratios of 1.7,2.5,3.5 and 4.5 were carried out based on related rock fragmentation mechanism at home and abroad.Meanwhile,a blasting calculation module was developed to study the crack propagation process and the response law of displacement based on the principle of near-field dynamics of conventional modes.The results show that the radial cracks present the character of branching to the corner of the free face and finally form the main cracks of a funnel shape,affected by the reflected tensile stress wave.Under the condition of fixed minimum resistance line,the stress reduction area gradually increases with the in-crease of the spacing-burden ratio,and the radial cutthrough cracks between the blastholes in the same row disap-peared.An excessive spacing-burden ratio will further cause the disappearance of the cutthrough cracks between two rows of holes,and finally lead to the occurrence of individual hole blasting.The displacement results further confirm the above rule,and the rock ridge left by the front row of holes is just broken by the rear row of holes when the spac-ing-burden ratio is small.This breaking effect gradually decreases with the increase of the spacing-burden ratio.It is suggested that the spacing-burden ratio should be appropriately adjusted according to the mechanical properties of rock mass,geological conditions and blasting purposes to reduce explosive consumption and boulder yield in practical projects.
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