低海拔季节性冻土明洞隧道常不考虑冻胀对明洞的影响，但此类隧道遇到冻害的概率极大，因此研究明洞隧道保温措施对隧道正常运营及行车安全具有重要意义。以低海拔季节性冻土区汗沟2号隧道为依托工程，利用Comsol Multiphysics有限元软件建立热力数值模型，研究不同种保温层铺设位置情况下隧道明洞的围岩温度变化规律，以及不同保温层厚度和不同回填厚度对明洞温度和衬砌应力的分布影响。结果表明：在明洞结构内外铺设保温层时保温效果都较好；无保温层铺设时，拱顶围岩处于负温状态，容易导致双向冻结，拱顶衬砌所受最大峰值应力为938 kPa，设置6 cm保温层时为547 kPa，降低了71%。保温层和回填厚度越大，围岩温度分布情况越有利，衬砌应力越小。研究成果可为类似低海拔季节性冻土区隧道明洞保温方案制定提供参考和建议。

The impact of frost heave on open cut tunnels is often neglected for seasonally frozen tunnels at low altitudes. However, these tunnels are highly susceptible to frost damages. Therefore, in order to ensuring normal operation and driving safety, the researches on effective thermal insulation measures for open cut tunnels in seasonally frozen regions is significantly important. Based on the Hangou No. 2 Tunnel which is in the low-altitude seasonally frozen region, a heat-stress numerical model was established by Comsol Multiphysics finite element software and the temperature changes of surrounding rock for various locations of insulation layer was analyzed. The temperature distributions of the open cut tunnel and stress distributions of tunnel lining were studied for different insulation layer thicknesses and backfill thicknesses. The results show that the insulation effects are very good when the insulation layer is placed outside or inside of the open cut tunnel lining. When there is no insulation layer the surrounding rock temperature. at the crown is negative It is easy to result in bi-directional freezing and the maximum peak stress of the crown lining is up to 938 kPa. When 6 cm insulation layer is used the maximum peak stress of the crown lining is reduced to 547 kPa, which is decreased by 71%. The greater the insulation layer thickness and backfill thickness, the more favorable the surrounding rock temperature distribution, and the smaller the tunnel lining stress. The research results can provide references and recommendations for establishing insulation plan of similar open cut tunnels in seasonally frozen regions.