PHYSICAL MODEL TESTING OF TEMPORAL VARIATION OF SOIL TEMPERATUE IN DEPTH

A physical model experimental system is developed in order to investigate the temperature variation with time in soil depth profile.The thermal conduction characteristics in soil profile with different surface covers but under the same heat source are compared and analyzed.The obtained results show that (a)the soil temperature increases quickly at the beginning stage and then tends to a relative stable value; (b)with increasing depth,the initial temperature increase rate of soil decreases exponentially; and (c)the final equilibrium temperature of soil also decreases with increasing depth.It is observed that the damping and retarding effects of soil temperature with depth are obvious.By comparing with bare soil,the initial temperature increase rate and final equilibrium temperature of soil with surface concrete plate cover are higher.The thermal flux in soil profile,which is measured by thermal flux plate,reflects the thermal conduction characteristics in time,and directly depends on the variation of temperature gradient between soil layers.