Abstract

The seismic forces must be properly defined as required by European geotechnical design Codes. They are dependent from the morphological and stratigraphic characteristics that determine the local seismic response. The local seismic response can be evaluated using a simplified approach which is based on the classification of the subsoil according to the values of the shear wave propagation speed Vs. In the present case study, to complete the quay of the Rovigo Interporto (facing the River Canal Bianco), where a not negligible load is planned to be applied (50 kPa), has been designed a foundation with a large slab founded with not pre-casted reinforced concrete piles diameter 350 mm, drilled without removing soil, with vibrating casing, for settlement reduction (rafted piles as settlement reducers), on an area of approximately 6000 m2. The subsoil in this area, from geological and geotechnical point of view, is very variable and with layers of soft clay and loose sand or silt, with no presence of a dense and uniform sand layer where to transfer loads to. Moreover, the geotechnical model was complicated because of the presence of an old diaphragm wall with anchors (whose projection in plant covers around half of area) and was designed a large underground basin for hydraulic invariance. For this reason, an extensive campaign of CPTU and DMT tests, together with boreholes, sampling and laboratory tests was carried out in this area, which allowed a detailed characterization of the subsoil. Through direct measurement of seismic micro-tremors, carried out before and after the installation of the piles, has been evaluated the modification of the resonance frequency of the site, and modification of the propagation speed of the shear waves Vs induced by the slab over rafted piles over the entire area.

Abstract

A new geotechnical site investigation has been conducted in the southern breakwater basin of the Port of Barcelona, for which hundreds of in-situ and lab tests have been performed. Among these tests, this study focuses on the evaluation of triple points. That is, at the prospected locations, there are results from seismic dilatometer Marchetti test (SDMT), cone penetration tests (CPTu), and laboratory tests based on soil samples. Based on this information, the probabilistic distribution of the dynamic and geometrical properties of the soil profiles can be properly characterized. Eleven closely spaced boreholes have been used to characterise the statistical properties of the input variables. The objective of this article is twofold. First, the probabilistic generation of one-thousand soil profiles, which are statistically compatible with the data provided by the eleven aforementioned boreholes. Secondly, to analyse how the elastic properties of the generated soil profiles evolve once seismic waves have passed through them. To do so, a large set of ground motion recorded in hard soils have been employed. Results show that the dynamic response of the soil can be properly parametrized if considering intensity measures extracted from the ground motions acting at the bedrock level. From the results obtained, fragility functions have been derived for risk assessment purposes.