To verify the persistence of the partial saturation condition, periodic monitoring is deemed necessary by measuring the propagation speed of elastic compression waves in the soil, whose value is particularly sensitive to the degree of saturation as shown in Septic Tank Installation.

Finally, periodic restoration interventions could be required if the ground becomes saturated, for this reason the injection pipes must be well protected against accidental breakage and be accessible and reusable over the years. The mixture percolates and diffuses into the soil releasing small bubbles of oxygen, which are trapped in the pores between the sand particles without disturbing the soil.

IPS techniques are much less expensive than active techniques, but to be used in the sites in question, they must be calibrated using a test field. The drainage technique can have the dual effect of limiting the occurrence of the liquefaction phenomenon, favoring the dissipation of the interstitial overpressures that are the cause, and reducing any induced deformations.

In particular, in sites where a low permeability layer present above a liquefiable layer can cause the entrapment of water under pressure with the formation of an interface of very low resistance or even of a water film, the dissipation and the redistribution of interstitial overpressures by the drains can be fundamental in preventing creep breaks and reducing lateral deformations.

The effectiveness of the drainage technique depends on the permeability and density of the soil, the wheelbase and vertical permeability of the drains, the type of filter used, the distance between the free surface of the water table and the drainage area of the drains, from the speed of the seismic load with respect to the liquefaction resistance of the soil.

Drainage does not produce any significant improvement in the mechanical characteristics of the affected soils. The use of drains without the simultaneous thickening of the soil may not be sufficient to dissipate interstitial overpressures during the most intense phase of the earthquake. In some cases the draining effect can be coupled with the consolidating effect through the creation of columnar elements of coarse-grained materials that are strongly thickened as shown in Septic Tank Installation.

If the geological-technical relationship identifies a terrain that is not able to withstand the loads and design stresses, then it may be convenient to improve the terrain itself by means of deep vibrocompaction procedures. They are applied in the most diverse soils and for the necessary depths.

The shape of the vibro tools is approximately cylindrical, their length is between 3e5m, their weight varies from approx. 2 t. The characterizing element of the vibro is the presence of an eccentric, housed at the lower end of the tool and driven by an electric motor. The vibrations transmitted to the ground have a prevalent horizontal component.