Ⅲ级硬岩隧道全断面光面爆破试验研究

Experimental Study on Full Face Smooth Blasting of Tunnel in ClassⅢHard Rock

光面爆破是硬岩隧道控制开挖的主要方法,由于爆破破岩机理与过程复杂,炮孔与装药参数设计粗放,因此实现隧道全断面光滑轮廓开挖较为困难。以寨山隧道Ⅲ级硬岩段工程为研究背景,首先采用大量的爆破试验和调查研究的方法,发现原爆破方案下,爆后隧道洞周轮廓拱部至边墙存在超挖、欠挖分布,以及存在盲炮、二次爆破施工等问题;其次,依据相关规范和工程经验,提出了光面爆破炮孔与装药参数的优化措施,包括减小周边眼间距、增加内圈眼数量、水袋间隔装药、炮泥堵塞和减小单孔装药量。结果表明:合理设计光爆层炮眼数量、单孔装药量,采用水袋间隔装药与炮泥堵塞,可提高装药爆炸能量的利用率,实现光爆层岩体的均匀破碎,有利于控制洞周岩体超欠挖。采用优化的光面爆破参数,爆后隧道全断面轮廓成形光滑、圆顺,炮孔残痕清晰,有利于提高隧道开挖质量和加快隧道整体施工进度。研究成果可为类似硬岩隧道全断面光面爆破开挖参数设计与优化提供一定的技术与方法借鉴。

Smooth blasting is the main method for controlling excavations in hard rock tunnels,but due to the complex mechanism and process of rock fragmentation by blasting,as well as the rough design of blast parameters,it is difficult to achieve a smooth excavation profile for the entire tunnel.This study focuses on the LevelⅢhard rock section of the Zhaishan tunnel,and through a large number of blasting tests and investigations,it was found that there were problems such as over-excavation and under-excavation,misfire,and secondary blasting construction around the tunnel profile after the original blasting plan was carried out.Based on relevant specifications and engineering experience,optimization measures were proposed for the blasting parameters,including reducing the spacing between contour holes,increasing the number of relief holes,using water bag as the charge decking and stemming,as well as reducing the amount of explosives loaded in each hole.The results showed that the optimization measures can improve the utilization of explosive energy,achieve uniform fragmentation of the rock mass,and control over-excavation and under-excavation of the tunnel perimeter rock mass.The blast parameter optimization also results in smooth and round tunnel profile with clear blast hole marks,which helps to improve the quality of excavation and accelerate the progress of tunnel construction.