开挖隧洞时,由于钻孔爆破及架立支撑等原因,使隧洞不可能获得准确的设计轮廓并引起某些开挖量的增加,这种增加的开挖量称之为岩石的超挖。由于架立临时支撑和布置开挖的施工机械设备而引起的超挖谓之“被迫的超挖”,由于岩石开挖方法所引起的超挖谓之“不可避免的超挖”,它们总称为“生产超挖” When excavating a tunnel, due to drilling blasting and erecting support, it is impossible to obtain the accurate design outline of the tunnel and cause some excavation volume to increase. This increased excavation quantity is called rock overbreaking. Due to the “temporary overthrowing” caused by the temporary support and arrangement of construction machinery and equipment for excavation, the “overbreak” caused by the rock excavation method is called “inevitable overbreak” For “production over digging”