【摘要】 风火山多年冻土隧道是青藏铁路的重点工程,隧道施工中对多年冻土的保护是一项关键技术。施工爆破对冻土的影响主要有两个方面:一是爆破造成围岩损伤,使围岩产生裂隙或使原有裂隙进一步扩展甚至贯通;二是炸药爆炸后产生高温、高压的爆生气体,巨大的热能影响冻土的热平衡关系。为了减小施工爆破对冻土的影响,根据理论分析及现场试验,研究相应的爆破方案,提出在明洞段采用预裂爆破,洞身段采用光面爆破,洞身段IV级围岩采取全断面开挖、V级围岩采用正台阶开挖的合理爆破方案,并优化爆破参数,提出在隧道掘进中对围岩最大爆破振动速度控制在5～10cm/s为宜。为解决施工热扰动问题,采用NaCl盐水炮泥封堵炮孔来达到降温防尘的目的。研究结果表明,水介质对爆生气体的降温效果为55%,而NaCl盐水介质对爆生气体的降温效果高达70%,降温效果十分显著。更多还原

【Abstract】 The Fenghuoshan Tunnel is an important project in Qinghai—Tibet Railway.How to protect permafrost during tunnelling construction is one of key technologies.There are two kinds of influences on permafrost because of the blasting construction:(1) firstly,blasting results in the damage of the surrounding rock,producing cranny in surrounding rock or making existed cracks spreading even connecting;(2) secondly,the explosion produces gas with high temperature and high pressure,tremendous heat energy influences the heat balance of permafrost.To minimize the effects on permafrost during explosion construction,the research on relevant explosion scheme is conducted based on the theoretical analysis and in-situ test.Presplitting blasting is adopted in the hollow segment;and smooth blasting is adopted in the tunnel body segment.The whole section excavation is considered in the tunnel body segment with surrounding rock grade IV;and the face step excavation is adopted for the tunnel body segment with surrounding rock grade V.Explosion parameters were optimized finally.The maximal explosion vibration velocity in the surrounding rock is controlled at 5–10 cm/s.To solve the heat disturbance problem,brine mud is adopted to block up explosion holes for cool and dustproof.The research result indicated the explosion gaseous cool effect when the brine mud medium was adopted reached 70% compared with 55% when the water mud medium was adopted,so the gaseous cool effect was significant.更多还原