Study on the Variation Rule of the Shallow Ground Temperature in Chongqing

In order to obtain the ground temperature variation rule (0 ~ 100m) of Chongqing, the annual monitoring of shallow ground temperature in multiple locations in the main urban area of Chongqing was carried out, and the ground temperature monitoring data are sorted and analyzed. The error and application scope of two common formulas in ground temperature prediction were analyzed, and the formulas in the domestic manual are optimized. The results show that the monitoring depth range of 0 ~ 100 m can be roughly divided into variable temperature zone (0 ~ 20 m), constant temperature zone (20 ~ 40 m) and increasing temperature zone (40 ~ 100 m). In the variable temperature zone, the temperature fluctuates regularly in a year. With the increase of depth, the temperature has the characteristic of hysteresis. The two commonly used formulas at home and abroad can predict the temperature in the variable temperature zone well. For constant temperature zone and increasing temperature zone, after introducing the local geothermal gradient into the formula in the domestic manual can make it has better accuracy. The average temperature of the constant temperature zone is 1.2 ℃~ 1.7 ℃ higher than the local annual average temperature, the ground temperature gradient in the increasing temperature zone is 1.4 ~ 2.1 ℃/100 m.