Correlation of direct and indirect compaction tests for various soils

Abstract

Continuous testing of subgrades during the initial stages of a project is necessary to ensure that an adequate compaction degree is being achieved to develop the strength required so that the subgrade functions properly as a foundation layer of a road pavement. The test procedures can be of a direct or indirect nature. The direct method of testing consists of the standard Proctor test performed in the laboratory to determine the maximum compaction degree that such a material is able to attain on site can be confirmed. Indirect tests include the Plate Bearing test that evaluates the reaction modulus of subgrades from which an indirect indication of the degree compaction can be obtained. Through out this dissertation various construction sites were Plate bearing tests were performed were considered from which soil samples were collected and the in place density and Proctor densities were evaluated in the laboratory to obtain a direct measurement of the compaction degree. The materials considered were Type 1 and General fill material from which a soil classification based on sieve analysis and plasticity data according to DIN18196 was obtained. By doing so correlations of direct and indirect compaction tests could be verified as a function of soil characteristics from which various relations were obtained. This research also includes various correlations between different types of field tests and effects produced by the subgrade strength on the strain developed below the asphalt layer.