The Frozen Depth and Its Prediction Affected by Shallow Phreatic Groundwater by Modified Berggren Equation

In order to study the influence of shallow phreatic groundwater on the maximum frozen depth of the subgrade in the seasonally frozen region, this paper verified the applicability of the modified Berggren equation predicting the maximum frost depth based on the monitoring geotemperature and air temperature in stratum whether the shallow phreatic groundwater does exist. The shallow phreatic groundwater lowers the mean geotemperature, delays it to the extreme value, and reduces the maximum frozen depth in the cold season. The shallow phreatic groundwater lowers the surface freezing index, which makes the average surface n-factor smaller. The influence of shallow phreatic groundwater on the thermal diffusivity of the stratum is small but has a significant influence on the thermal conductivity. The slope of the modified Berggren equation is almost unaffected by shallow phreatic groundwater, and the applicability of the equation predicting the maximum frozen depth is verified based on the thermal conductivity calculation, no matter the shallow phreatic groundwater does exist.