The response regularity of temperature and humidity of surface soil on slopes in high-cold and humid areas

Previous studies on the temperature and humidity of slopes in cold and humid areas based on long-term in-situ monitoring are insufficient. Therefore, a soil-rock slope along the Shuangda Expressway in Gansu Province is selected as the research object, and the humidity and temperature of shallow soil and rainfall are monitored for more than two years based on the constructed remote monitoring system. Combination of the Fourier model and Pearson correlation analysis, the soil moisture-heat migration at different depths and rainfall infiltration law are explored, and the interaction relationship between temperature and humidity is analyzed. The results show that the temperature and humidity of shallow soil change periodically in a harmonic way, and the variation range decreases gradually with the depth. In March and September, the temperature curves of each soil layer showed a ‘knot’ phenomenon, which impels the slope to change from one condition characterized by hot outside and cold inside in spring and summer to another condition characterized by cold outside and warm inside in autumn and winter. The change in mean monthly temperature of soil at a depth of 2 m has a certain lag, and the lag time is about 30 days. The depth of rainfall infiltration can occur only within the depth of 50 cm in spring, while the rainfall can infiltrate into deeper soil in summer, and the moisture content of soil stays above 35% because of sustained replenishment by rain. Soil temperature and humidity have a highly positive correlation, the correlation increases with soil depth and the correlation in different periods shows a "circulating ring" effect. The research results may provide some reference for further understanding the eco-hydrological response of soil, the water-heat correlation and the mechanism of surface erosion in terms of slope.