RELATIONSHIP BETWEEN TYPE AND CONDITION OF SOIL IN THE SUBGRADE AND THE DYNAMIC E-MODULUS (MEAN MODULUS) OF THE SOIL DURING DIFFERENT SEASONS OF THE YEAR. A PRELIMINARY INVESTIGATION

The aim was to obtain information on the loadbearing capacity, expressed as a dynamic e-modulus value, of different types of soil and the way in which the e-modulus varies with the condition of the soil when this constitutes the subgrade for a gravel road pavement. The e-modulus value has been estimated from falling weight tests. Ground investigations, water ratio analysis and measurements of frost depth have been made in order to describe the various types of soil and their condition. The results of the investigation indicate the following: (1) e-modulus values vary during ground thaw between 14 mpa for a subgrade of silt on clay and 143 mpa for a subgrade of sand with inclusions of coarser material, (2) unexpectedly high e-modulus values for morainic subgrades during ground thaw were obtained, (3) an unexpectedly small decrease was found in the e-modulus value during ground thaw. The largest decrease was found in silt on clay, (4) a clear relationship between the e-modulus and particle size distribution was found in the sedimentary subgrades but not in the morainic subgrades, (5) no clear relationship was established between the e-modulus and the water ratio in each type of soil. These results have been obtained during one year studies. The measurements will continue so that the significance of the results can be clarified. (Author/TRRL)