DROP MASS COMPACTION OF SOIL

In one aspect, the invention concerns a method of compacting soil which involves the steps of repeatedly raising a mass (28) above the soil surface and then dropping it to apply impacts to the soil surface. Indications of one or more instantaneous properties of the soil are periodically derived from the impacts on the soil surface. In accordance with these indications, the number of subsequent impacts and/or the energy imparted to the soil at each impact and/or the frequency of the impacts is or are controlled automatically by a controller typically in the form of a PLC in order to achieve in the soil one or more predetermined properties. In another aspect the invention concerns a soil compaction apparatus (10) that includes a drop mass soil compactor having a mass (28) and means (30) for repeatedly linearly raising the mass above the soil surface and then dropping it to apply impacts to the soil surface. The apparatus also has a monitoring means (42) arranged to provide periodic indications of one or more instantaneous properties of the soil; and the abovementioned control means (44). Still further invention concerns a method and apparatus for measuring instantaneous soil properties on a site.