overcompaction

Some compaction of sand fills, especially in earthquake regions, is essential to prevent flow slides (Art. 8-11). On the other hand, there is some question whether excessive compaction of any type of fill is necessary when the underlying soil is comparatively weak. It appears possible that such overcompaction may even be detrimental, since it will provide a comparatively rigid superstructure which may be overstressed while adapting itself to the deformations of the underlying weaker material.

1951, Gregory Porphyriewitch Tschebotarioff, Soil Mechanics, Foundations, and Earth Structures: An Introduction to the Theory and Practice of Design and Construction, McGraw-Hill, page 560

For adequate subgrade design, several basic principles should be followed at all times, including proper compaction of the subgrade, installation of adequate subdrains, and adequate field control. The design values which are used for the design of pavements are generally based upon the results of soaked laboratory tests. The tests should be made only after a study of the moisture-density-strength relationships of the various subgrade soils are determined. Arbitrary selection of standard densities and moisture contents gives results satisfactory for most routine work; however, a careful study should be made of all the variables affecting the strength of the soil. If the laboratory tests indicate that the subgrade will lose strength with increasing densities due to overcompaction, careful consideration should be given to closely controlling the moisture content. It may be necessary to limit the maximum weight of roller to be used.

1959, Principles of Pavement Design, John Wiley and Sons Incorporated, page 252