The method heavy tamping consists in producing an increase in the relative density of liquefiable soils by free fall from heights of up to 30-40 meters of large concrete or steel blocks weighing up to tens of tons, causing compression waves due to sudden release of energy, which generate an instantaneous increase of pore pressure, reducing the shear strength in the soil by inducing a series of subsequent liquefaction. When the excess pore pressure dissipates, the particles reach new, more stable, configurations.
The procedure normally requires 2-3 shots per m2. At the end is advisable to run a check, for example, penetration tests, in order to establish that the soil has actually achieved an increase of the relative density. The tests will be performed up to a depth of densification influence, depending on the weight of the mass W and the fall height H and is evaluated by the empirical expression:
where W is measured in tons D and H in meters.
The success of this method on natural soils is not always guaranteed, especially if there is a percentage of fine content greater than 10%; instead were obtained excellent results in densification of landfills.
The method heavy tamping is simple and quick at acceptable costs, from which it also derives a good uniformity of treatment. However, it can’t be used in the vicinity of existing structures given that the vibrations produced induce harmful effects on the structures.
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