Structural engineers often ask geotechnical engineers if the insitu liquefiable soil (site class F) in a project site can be improved so that the foundation soil is classified as E or D. In order to answer this question, the geotechnical engineer should evaluate the soil condition and find a method to mitigate liquefaction. There are many efficient ground improvement (GI) techniques by which liquefaction can be mitigated.

GI techniques such as vibro-densification, stone column, rapid impact compaction, and deep dynamic densification mitigate liquefaction by densifying soils and increasing insitu lateral stresses. This will result in significant increase in soil cyclic resistance ratio (CRR). By the increase of CRR, factor of safety against liquefaction becomes greater than 1.0, i.e., low potential for liquefaction. By the mitigation of liquefaction, soil can be classified as E or D depending on the magnitude of V_{s,30}.

Another approach to modify site class is installation of deep soil mixing (DSM) columns in a cellular pattern. This technique does not densify the soil or increase lateral stresses. The DSM cells constrain the soil inside cell and because of its large stiffness, the cell prevents excessive deformation of the soil. Due to small shear deformations of the soil, pore water pressure slightly builds up during seismic shaking. Therefore, soil does not liquefy, and it can be classified as E or D depending on the magnitude of composite V_{s,30}.

Note that all of the above-referenced techniques have some limitations. All densification techniques  would be less effective if the liquefiable soil contains too much fines content ( >20%). In fine sands or silts densification will not occur as a result of any source of vibration. Cellular pattern of DSM columns are effective in any type of soil but they can be very expensive ground improvement solution.