Effects of diurnal temperature rhythm on the geothermal regime under the embankment in Qinghai–Tibet plateau

Abstract

The objective of this study was to investigate the effects of diurnal temperature fluctuation amplitude (DTFA) on the geothermal regime of the embankment on the Qinghai-Tibet plateau. The investigation was simulated by respectively denoting the diurnal temperatures at the embankment surface, embankment slope, and natural ground surface with sinusoidal waves. The amplitudes of the waves were denoted by 0°C, 5°C, 8°C, and 12°C, respectively. The numerical result shows that the DTFA cannot vary the frequency of the seasonal temperature fluctuation of the underlying soil, but can significantly change the magnitude of the soil's temperature. The changes include: (1) The high DTFA, such as 12°C, can significantly lead to the warming of the soil under the embankment. (2) Interestingly, when the DTFA at ground surface is 5°C, the underlying soil is in a cooler stage compared to when such DTFA is 0°C, 8°C, or12°C. This interesting result means that the documented model which ignores the diurnal temperature rhythm overestimates the warming of the underlying soil at the low DTFA region and underestimates such warming at the high DTFA region. This result also suggests that the soil under the embankment can be cooled down if the DTFA on the ground surface was maintained at or approximately at 5°C.

A heat-flux upper boundary for modeling temperature of soils under an embankment in permafrost region

“…Equation ( 2 ) considers the daily temperature only, although some models occasionally take the daily temperature pattern into account 14 . As the ground-surface temperature is difficult to be measured directly, T 0 and A are coarsely estimated from the annual air temperature (data from the nearly weather station) according to the adhesive layer theory 15 .…”