Study on the evaluation method of heat transfer characteristics of rocks with cracks for the development of the deep ground.

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A personal computer system and a program to capture thermographs was developed for the analyses of laboratory experiment of the heat flow in the ground and then the heat transfer in the porous media saturated by pore water was examined using a small model ground. In this experimental equipment the ground with different permeability can be constructed and any amount of ground water flow can be given by changing the water head. A FEM program was also developed to analyze the experimental results and to evaluate the thermal constants of the constituents. Comparing the theoretical results and experimental ones, effect of water flow to the apparent heat conductivity of soil was studied, and it was found that there are strong effect of convection of heat by pore water on the heat conductivity of soil as a whole and an empirical equation proposed by De Vries gives an accurate values of heat conductivity of the soils.Application of percolation theory and equivalent inclusion method to the estimation of thermal constants of soils were examined last year and it was already concluded that these theories are not always convenient to evaluate the thermal constants of soils because the theoretical estimation always contains errors caused by assumption of structures and averaging procedures. In addition to that it was found that the proposed method of FEM calculation gives enough accurate results compared to the values estimated from these two theoretical assumptions. Therefore analytical studies by use of percolation theory and equivalent inclusion method was excluded from the studies of this year.