隧道掘进中岩体质量对爆破质量的影响

定义了描述隧道掘进中爆破质量的参数———炮孔利用率(η)、超挖(OB)和半孔率(HCF),考查了岩体质量对这些参数的影响。按照Bieniawski准则,以RMR作为岩体质量的指标,而按照Hoek Brown准则,以Ram作为岩体质量的指标。根据对不同地质条件、不同开挖技术的17个隧道掘进段的研究,确定了RMR和Ram与η、OB以及HCF之间的关系。研究表明,在必须为隧道爆破作业规定质量参数临界值时,岩体构造有不可忽视的影响。研究发现,当岩体质量较差时,使用先进的钻孔方法或昂贵的设备对提高爆破质量不会有任何好处。同时还发现,HCF是一个敏感的爆破质量指标,随着岩体质量的提高,该指标显著增大。

ON THE INFLUENCE OF ROCK MASS QUALITY ON THE QUALITY OF BLASTING WORK IN TUNNEL DRIVING

After defining the parameters describing the quality of blasts in tunnel driving-the efficiency,the over-break and the HCF factor,the paper examines the influence of the quality of rock mass on said parameters. As indicators of the quality of the rock, the RMR according to Bieniawski and the rock mass strength according to Hoek and Brown criterion are assumed.On the basis of observations in more than 17 stretches of tunnels in different geological conditions and excavated with different techniques,it has been possible to outline the relationships between RMR and rock mass strength and the blasting efficiency,the over-break and the HCF.It is concluded that the rock mass structure has a not negligible influence when a quality threshold has to be set for a tunnel blasting operation;the threshold values as suggested by observation are indicated.Moreover,it has been found that the use of sophisticated drilling systems,using expensive equipment,does not provide advantages in cases of rock masses of poor quality.Finally,it has been found that HCF is a sensitive indicator of the quality of blasting,and that the same factor increases in an evident manner as the rock mass quality improved.