Validity of Menard relation in dynamic compaction operations

Dynamic compaction (DC) is a common soil improvement technique, used extensively worldwide. DC treatment design is usually based upon empirical relations and past experience. The common problem with all empirical relations is oversimplification of the mechanisms, and the use of parameters that are highly dependent on engineering judgement. In this paper, a developed finite-element code is used for modelling the impact behaviour of dry and moist sandy soil. The code is verified against the results of centrifuge tests. Then the validity of the popular Menard empirical relation for determination of improvement depth in DC design is investigated. The effect of initial relative density, tamper radius, number of drops, and the impact energy are studied using the developed numerical model. It was found that Menard's empirical relation yields suitable results when tamper weight and falling height are both in the ordinary ranges. However, for higher impact energies, Menard's relation overestimates the depth of improvement. The obtained results also indicate that the value of the empirical coefficient in Menard formula depends strongly on the applied energy and tamper radius. Based on this finding, a new relation for predicting the improvement depth is proposed and applied to a number of DC projects. The results show that the new relation provides better results than the old formula.