The researchers used computer simulations to study how adding insulation to tunnels in cold areas can prevent frost damage. They found that using a certain type of insulation material and laying it in a specific way can significantly reduce heat loss and protect the tunnel structure from freezing. They recommend using a wall-attaching style insulation layer that is at least 5.5 cm thick and has a thermal conductivity coefficient between 0.025 and 0.04 (W/m.k). Additionally, when temperatures drop below -17 °C, extra insulation measures should be taken to ensure the tunnel remains frost-resistant.