Automatic Measurement of Highway Subgrade Temperature Fields in Cold Areas

Aimed at solving the problems of complicated external environment and impossible continuous automatic measurement in the observation of highway sub grade temperature fields in cold areas, an observation system of temperature is assembled with DS18B20 temperature sensor, STC89C58 single chip, DS12C887 clock and AT24C256 external memorizer, which is powered by lithium batteries. Automatically collecting, saving and continuously observing sub grade temperature are realized by this system. According to the data collected in this measurement, temperature of sub grade is less affected by atmosphere temperature as sub grade depth increases during a period of freezing and thawing cycle. Average variation range of sub grade temperature is small and above 0°C when sub grade depth is below 2.0m. Frost depth gradually descended before the middle ten days of February, then rose after the time. Because caloric transfer coefficient of sub grade soil is rather small, caloric transfer is very slow in soil. So the variation of sub grade frost depth is a month later than that of atmosphere temperature. The measuring results can provide basis for analysis of sub grade frost-heave damages in cold areas.