独头隧道钻爆法施工爆生气体扩散过程模拟

Simulation of Diffusion Process of Harmful Gas Produced by Drill-blast Construction in One Ended Tunnel

为研究隧道钻爆法施工产生的有害气体压入式通风效果,以我国成兰铁路跃龙门隧道工程为依托,通过建立独头隧道内气体湍流流动与浓度扩散有限元模型,模拟风机出口风速13.2 m/s时,掌子面爆破作业后爆生有害气体的扩散过程,研究了不同风管布设位置与施工方法下CO浓度场时空演化规律。研究结果表明:掌子面CO浓度随通风时间呈负指数下降,CO浓度在300~900 s内到达浓度限值。对比各风管布设位置,风管拱顶布设时通风效果最好,通风600 s内CO浓度可降低至浓度限值。对比各施工方法,台阶法施工下通风350 s内CO浓度可降低至浓度限值,同时该隧道结构能够避免通风前期的CO滞留现象。

To explore the forced ventilation effect of the harmful gas produced by drill-blast construction,a finite element model is established to show gas turbulent flow and concentration diffusion in a one ended tunnel,based on the Yuelongmen tunnel project of Chenglan railway in China.When the wind speed at the exit of the simulated fan is 13.2 m/s,the diffusion process of the harmful gas produced by blasting at the working face of the tunnel is simulated.Meanwhile,the temporal and spatial evolution law of CO concentration field for different positions and excavation modes of the air duct is studied.The results show that CO concentration at the working face decreased negatively with the ventilation time,and the CO concentration reached the concentration limit within 300~900 s.Comparing the layout position of each air duct,the ventilation effect is best when the duct arch is laid,and the CO concentration within 600 s of ventilation can be reduced to the concentration limit.Comparing the construction methods,the CO concentration in the 350 s ventilation under the bench method can be reduced to the concentration limit.At the same time,the tunnel structure can avoid the CO retention phenomenon in the early stage of ventilation.