The testing sites are chosen on the basis of the following main criteria:
- availability of geological and geotechnical data,
- presence of liquefiable soil deposits where liquefaction manifestations possibly occurred during past earthquakes,
- representativeness of different geological setting, populated areas.
Emilia region in Italy
Lisbon area in Portugal
Ljubljana area in Slovenia (by the Lower Sava river)
Marmara region in Turkey
Specific sites within the above four regions will be purposely selected and characterized from the geomorphological, geological, hydrogeological, seismological, geotechnical, and geophysical viewpoint.
Existing data on quaternary deposits and man-made landfill, geomorphological maps, trench pits, boreholes, piezometric, geotechnical (in situ and laboratory) and geophysical data will be collected. Data obtained from past investigation campaigns performed by some partners of the consortium (e.g. UNIPV in Emilia region) will be made available and used. All these data and metadata will be stored and analysed, within a GIS environment, in order to identify homogeneous geological units (areas that may be regarded as homogeneous from the engineering geology point of view) susceptible to liquefaction. Based on the quality and quantity of the gathered existing data, complementary ground investigation campaigns will be purposely planned and executed at the case study sites focusing the study on local sands, silty-sands or even non-plastic sandy-silts deposits, in view of a fundamental evaluation of their susceptibility to liquefaction.
Among the in-situ geotechnical tests that will be included in the complementary ground investigation
campaigns are the cone penetration tests (CPT) with acquisition of the excess pore pressure (CPTu) and the shear wave velocity Vs (SCPTu), flat dilatometer tests (DMT) with acquisition of Vs through the seismic dilatometer (SDMT), standard penetration tests (SPT), pressuremeter tests (PMT). Furthermore, geophysical tests such as spectral analysis of surface waves, SASW, multi-channel analysis of surface waves, MASW, down-hole, cross-hole, and electric tomography are also included in the plan of the complementary investigation campaign at the case study sites. Geophysical prospecting will allow the “illuminating” of large volumes of soils thereby permitting the correlation of the results obtained at different locations from the conventional geotechnical tests.
Although, the actual execution of the complementary experimental tests at some regions would be
subcontracted, the project partners will take full responsibility for the planning, coordination, surveillance and interpretation of the results. Depending on the available data, ground characterization may also include laboratory tests on specimen sampled at the selected sites. Given the granular nature of sandy soils, undisturbed sampling may be difficult. High-quality undisturbed samples will be retrieved using innovative and cost-effective techniques such as the “gel-push sampler”. The undisturbed samples will be tested using different devices, including the cyclic triaxial (CTx), cyclic direct simple shear (CDSS), and conventional triaxial compression (Tx-BE) tests, with P and S wave measurements to identify some of the factors that control soil behaviour, particularly under seismic excitation. As described in WP4, one of the four selected sites for the case studies (Emilia, Italy site) will be treated to investigate the effectiveness of different liquefaction mitigation techniques. At this case study pilot site, a suitable set of geotechnical and geophysical tests will be performed to assess the efficacy of soil treatment.