Significant and widespread liquefaction effects, which caused panic of inhabitants and damage to buildings and infrastructures, were observed in various areas of Emilia-Romagna region, Italy, during the seismic events of May 20 and 29, 2012, with magnitude respectively of Ml 5.9 and Ml. 5.8. In Italian seismic literature these phenomena represent an interesting case study for a number of reasons: for the exceptional impacts, for the size of the area in which liquefaction effects were observed, for the amount of damage produced, for the rarity of soil liquefaction Italian case histories. Immediately after the earthquake of 20 May an extensive field reconnaissance was conducted through the natural and built environment to capture as quickly as possible surface evidences of liquefaction and to document the extent and the severity of damage. The most significant and widespread liquefaction impacts were found in the two settlements of San Carlo and Mirabello. With the aim of a better understanding of the observed scenarios, a detailed investigation program, including geophysical surveys and geotechnical testing (soundings, cone penetration tests, seismic cone penetration tests, cross-hole and down-hole tests as well as many cyclic laboratory tests), was planned. These investigations are now in progress and will be object of forecoming technical notes. This paper summarizes the observation of soil liquefaction effects made during field investigations and presents a first interpretation, based on available information on ground shaking and soil conditions, of the factors that may have contributed to determine the low liquefaction resistance of soils.
liquefazione
Simple considerations of liquefaction due to earthquakes and flow failures of slopes in sandy soil
This paper summarizes briefly the existing methods for the analysis and presents simple considerations of liquefaction potential due to earthquakes and flow failures of slopes made of sandy soil for eight case histories in order to indicate the accuracy and usefulness of the simple considerations in routine engineering practice. Simple consideration of liquefaction potential of slopes in sandy soil during earthquakes is based on calculation of factor of safety of slope stability before liquefaction using pseudo-static limit equilibrium method, the shear to axial stress ratio defined using the equivalent sliding block method and the empirical charts used for assessment of liquefaction potential of level ground. Simple consideration of flow failure of sandy slopes is based on Bernoulli’s equation for conservation of energy along a flow line of incompressible fluid.