Field tests to assess the effectiveness of ground improvement for liquefaction mitigation

One of the main goals of the LIQUEFACT project is the analysis of the effectiveness of some ground improvement techniques in the mitigation of seismically induced soil liquefaction risk. This aspect was addressed via a comprehensive experimental program by means of laboratory and centrifuge tests, as well as by carrying out a number of tests in a field trial located in Pieve di Cento (Italy), where a shaker was placed at ground level to generate cyclic shear stresses at ground level to induce a significant build-up of pore pressure in the shallow liquefiable sandy layer. Three series of tests were carried out: one in a zone without treatments (UN), one in a zone where horizontal drains (HD) were installed in the liquefiable layer, and one in a zone in which air was insufflated through sub horizontal pipes to partially desaturate the liquefiable soil (induced partial saturation, IPS). The paper describes in some detail the test layout and reports the results obtained during some of the tests carried out. The vibrator was able to generate high pore pressure build-up in the untreated zone, locally inducing liquefaction in one of the tests. IPS was extremely effective in reducing pore pressure increments during shaking, with values close to zero. This confirms the potential of this innovative liquefaction mitigation technology.