Soil grouting for the seismic protection of existing buildings

Seismic risk is one of biggest challenges for civil engineers, and over the years a number of mitigation strategies have been developed with reference to existing or new buildings. Currently in 2014, there are refined techniques based either on structural reinforcement or seismic isolation that aim to protect new and existing structures from seismic shaking. Some results of a research activity that is in progress at the University of Napoli Federico II (Italy) are presented. The study aimed to check the effectiveness of an innovative approach for reducing the seismic risk by using soft grouting mixtures installed at an optimum depth in the foundation soil. The basic idea is that a thin grouted layer, with dynamic impedance that is much smaller than that of the surrounding soil, will filter and reflect most of the seismic ground motion, with very little energy being transmitted to the overlying soil. The effectiveness of the insertion of a soft grouted layer in the range of frequency affecting the response of squat buildings was numerically tested via parametric analyses, with reference to a simplified one-dimensional scheme.