关键词: 温度示踪, 浅层地温场, 热对流, 傅立叶级数

Abstract:

The study areas of temperature tracer method are mostly concerned with shallow layer, its temperature is mainly influenced by weather and groundwater. Fluctuation of air temperature can be accurately expressed by Fourier series. How surface temperature and vertical groundwater flow influencing temperature field were demonstrated with a transient analysis model. The analytical solution is obtained by Laplace transform and numerical solution by FEM. The results indicate that shallow ground temperature field also has seasonal fluctuation; but the decay rate of amplitude mitigates singnificantly; and fluctuation of air temperature can influence deeper in groundwater recharge district: while in discharge district, amplitude of temperature waves decays faster. Besides, a transient temperature field near horizontal strong leakage layer is simulated. It is found that because heat transfer ability of convection is much stronger than conduction, the temperature within strong leakage zone is consistent with recharge source quickly and then temperature field in a wider range is changed by conduction. Geologic bodies near low temperature source are cooled faster and changed more, vice versa, slower and less. Therefore, the potential leakage zone can be traced accurately in this way.

Key words: temperature tracing, shallow ground temperature field, thermal convection, Fourier series