Abstract: There are many challenges in the construction of long tunnels in high altitude areas. Ventilation in the construction of long tunnels at high altitude under the conditions of low pressure and low oxygen content is an important research topic. In the existing engineering practice of construction ventilation of long tunnels at high altitude, the ventilation mode of combination of the forced type and roadway type was mostly adopted, and the length of forced ventilation section was determined only by construction experience and construction task. The theoretical research on the demarcation of length between the forced type and roadway type was rare. At present, the research on the forced ventilation distance mainly focused on the analysis of the limit ventilation distance under specific conditions, which was a lack of direct calculation of the forced ventilation length without considering the construction process. Based on the principle of flow conservation, combining with the experience of the forced ventilation in tunnel construction in low altitude areas, the optimal length correction formula of tunnel forced ventilation in high altitude area was obtained. Based on the theoretical formula used in the construction of Mila Mountain Tunnel Project, the ventilation scheme was developed, and the dust concentration and CO concentration in the tunnel at 30 minutes after excavation and blasting were monitored and recorded on site. The feasibility of the theoretical formula was verified by analysis.

Key words: tunnel engineering, high altitude tunnel, construction ventilation, forced ventilation, optimal ventilation length

摘要： 高海拔地区长大隧道的建设面临诸多挑战，在低气压、低氧气含量条件下的高海拔长大隧道施工通风问题是其中一项重要的研究课题。现有高海拔长大隧道施工通风的工程实践多采用压入式与巷道式相结合的通风模式，且仅靠施工经验及施工任务来确定压入式通风段的长度，关于压入式与巷道式之间的长度界限划分的理论研究还较少见。目前关于压入式通风距离的研究主要是特定条件下的极限通风距离分析，存在未考虑施工工序导致无法直接计算出压入式极限通风长度的不足。基于流量守恒原理，结合低海拔地区隧道施工压入式通风经验得到高海拔地区隧道压入式通风的合理长度修正公式，依托在建米拉山公路隧道工程运用理论公式制定通风方案并在现场对开挖爆破30 min后隧道内粉尘浓度和CO浓度进行实时监测记录，分析验证了理论公式的可行性。

关键词: 隧道工程, 高海拔隧道, 施工通风, 压入式通风, 合理通风长度