Study on the geometric parameters of elbow ventiduct embankment in permafrost regions along the Qinghai-Tibet Engineering Corridor

Abstract Using cold air to cool down infrastructures in permafrost regions is a common technique, but the horizontal ventiduct method has defects. This paper presents the elbow-shaped ventiduct and focuses on its designing parameters, considering the regional climate along the Qinghai-Tibet Engineering Corridor. Based on the natural convection principle, a program for calculating the parameters of the elbow ventiduct of embankment is compiled. By using this program and according to the climatic conditions, the required freezing radius of elbow ventiduct is calculated, and the specific thermal parameters of elbow ventiduct in different climatic regions are calculated. Results show that the lower the average temperature is, the smaller the required freezing radius is. The required freezing radius at Anduo, Kaixinling, Liangdaogou, and the Buqu Valley are 2.45 m, 1.7 m, 1.13 m, and 0.54 m, respectively, and the corresponding longest horizontal pipes that can be used are 32 m, 101 m, 228 m and 799 m, respectively. The regions where the elbow-shaped ventiduct are not suitable or not necessary are figured out. Results also show that the bigger the pipe diameter, the longer the maximum allowable length of horizontal pipe; the higher the vertical pipe length, the longer maximum allowable length of horizontal pipe.