Research on Characteristics of Ground Temperature Variation in Tianjin

In order to meet the needs of underground space development and construction in Tianjin, the changes of ground temperature were analyzed and studied based on 38 sets of ground temperature test data of the subway project, and the law of ground temperature changes with environmental temperature and stratum burial depth were found out. The method for determining the depth of the constant temperature layer in this area and the fitting calculation formula of the constant temperature are given. The buried depth and temperature of the constant temperature layer in the central city, the four districts around the city and the Binhai New Area are further studied. The results show that when the ground temperature in Tianjin is stable, the average depth is 8～10 m, and the stable temperature is generally 13～17 ℃. The ground temperature varies drastically with depth in the range of 0～10 m, while it is relatively stable in the range of 10～25 m. The depth of the constant temperature layer in Tianjin can be determined by the minimum depth corresponding to the temperature change rate decreasing to 0.2 or below on the relationship curve between ground temperature and depth, and the constant temperature can be determined by formula calculation based on the average temperature and monthly average temperature. The buried depth of the constant temperature layer in each district is generally about 10 m on average, and the average constant temperature is 16 ℃.