THEORETICAL AND PRACTICAL ASPECTS OF THE THERMAL CONDUCTIVITY OF SOILS AND SIMILAR GRANULAR SYSTEMS

Abstract

THE THERMAL CONDUCTIVITY OF SOILS AND ALLIED PHENOMENA PLAY A MAJOR ROLE IN SEVERAL ENGINEERING FIELDS. A FEW EXAMPLES ARE THE FROST PROBLEM IN HIGHWAY ENGINEERING, THE DISSIPATION OF THE JOULE HEAT FROM BURIED ELECTRIC CABLES, AND THE THERMAL EXCHANGE IN HEAT PUMP SYSTEMS. IT IS NOT TOO DIFFICULT TO MEASURE ACTUAL HEAT CONDUCTIVITIES OF PARTICULAR SOILS AT SPECIFIC MOISTURE, DENSITY, AND STRUCTURAL CONDITIONS. HOWEVER, THE VALUES OBTAINED CAN BE USED FOR PURPOSES OF PREDICTION WITH REGARD TO THE NORMAL WEATHER -- AND SEASONALLY CONDITIONED CHANGES IN SOIL PROPERTIES ONLY BY MEANS OF ADEQUATE HYPOTHESES AND THEORIES. THE MORE CLOSELY THE THEORETICAL CONCEPTS DEPICT THE ACTUAL MECHANISMS OF HEAT TRANSMISSION IN SOILS, THE FEWER HEAT CONDUCTIVITY MEASUREMENTS MUST BE MADE AND THE MORE USEFUL TO THE ENGINEER ARE THOSE THAT ARE MADE. SOILS NORMALLY CONSIST OF SOLID, LIQUID AND GASEOUS PHASES, AND THE MECHANISM OF HEAT TRANSMISSION DIFFERS FOR THESE DIFFERENT STATES. THEREFORE, THE PAPER DISCUSSES THERMAL TRANSMISSION IN SOLID, LIQUID AND GASEOUS PHASES BEFORE TREATING THE MORE COMPLEX SOIL SYSTEMS. THE VARIOUS THEORETICAL AND EMPIRICAL EQUATIONS AVAILABLE FOR THE SIMPLE AND COMPLEX SYSTEMS ARE ANALYZED AND RESULTS OBTAINED WITH THEM ARE COMPARED WITH ACTUAL EXPERIMENTAL DATA. THE INADEQUACY OF THE PRESENT THEORIES CONCERNING THERMAL CONDUCTIVITY IN SOILS IS POINTED OUT AND WAYS TOWARD CORRECTING SOME OF THE DEFICIENCIES ARE INDICATED. /AUTHOR/