The paper presents results from an extensive experimental model study of response of dry sand to impact of a rigid tamper. In the laboratory tests a circular steel tamper was repeatedly dropped on sand contained in a large tank. Measurements included tamper acceleration aud soil pressure at impact, tamper settlement, aud soil densities and strains. Effects of tamper drop height, weight and contact area were investigated. A method is presented for the evaluation of global dynamic stiffness of the soil mass affected by the impact by calculating a dynamic settlement modulus (DSM). The DSM values are determined from integration of the impact acceleration record with respect to time using measured integration constants. DSM values show good correlation to soil densities and corresponding elastic moduli obtained from laboratory tests for loose sand. However, for dense sand, results indicate apparent discrepancies between elastic modulus and the higher DSM values. Analyses of normalized impact energy and the resulting densification in the sand in terms of normalized dimensions of volumetric strain (relative density) contours show unique correlations which are used for a proposed rational design method for dynamic compaction in dry sandy soils.
