The criteria for the compaction control can be fixed in terms of relative density, specific value of cone resistance, modulus of deformation and soil settlements on the trial field. CPTU is particularly useful when a certain relative density over the compacted strata should be obtained. Taking into account the soil mineralogy and compressibility at a given site, the suitable correlation – established from calibration chamber tests – between the cone resistance and relative density should be applied. The improper estimation of the sand compressibility can produce the uncertainty in the evaluated relative density up to 20%. One should also remember that these correlations are established from calibration chamber tests on freshly deposited sand, their use for in-situ conditions and in aged or cemented sands gives an equivalent relative density (Schmertmann et al. , Jamiolkowski et al. ).
The choice of a specific value of cone resistance as a compaction criterion over the strata considered will produce an excessive compaction effort in the upper layers and non uniform soil densification. The better solution is to express (Massarsch and Fellenius ) compaction specification as a cone resistance value adjusted to mean effective stress. If the compaction requirement is to obtain a minimum modulus of deformation in the strata considered, then the dilatometer or pressuremeter is a very useful tool to check the compaction effectiveness. The constrained modulus from dilatometer test MDMT can be considered simply as one-dimensional, compression modulus M, because the settlement observations of the real structures (Schmertmann , Marchetti et al. ) are very consistent with those calculated with the constrained moduli from DMT (i.e., M ≈ MDMT). Values of the constrained modulus from DMT can be thus compared directly to the fixed criterion. When a minimum value of the relative density should be obtained in the compacted strata, the DMT is useless because no method is available to derive the relative density from dilatometer test data alone (Marchetti et al. ).