GNGTS 2016 - Atti del 35° Convegno Nazionale

GNGTS 2016 S essione 2.2 357 Numerical simulations of RSL performed at Casentino used strong motion records of seismic events recorded at seismic stations belonging to national and international networks. In this study 1D and 2D numerical analyses have been carried out using the seismic input of the L’Aquila earthquake of April 6, 2009 (Pace et al. , 2011). Two-dimensional numerical simulationshavebeenperformed by the FEM commercial code LSR 2D (Stacec, 2015). Results from FEM simulations are reported in Fig. 2: as can be noted the Casentino site amplifies the input accelerations up to 5 times. Compared with the spectra suggested by the Italian technical code (NTC08), 2D numerical analyses show higher amplifications for large period intervals, ranging between 0.2 and 0.9 s. The amplifications have been calculated according to factors suggested by “Indirizzi e Criteri per la microzonanzione sismica” (ICMS, 2010), in terms of the amplification factors FA. Considered Housner’s Spectral Intensity H A X : where SA is the acceleration spectra and Ti and Tf are the lower and upper limits of the range of periods, the amplification factor FA is defined as the ratio between Housner’s Spectral Intensity of the output divided by the input at different calculation points: The FA values calculated through 1D simulations range from at least 1.6-1.8 up to at most 3.8- 4. These results enable to state that the sections with a non-horizontal ground surface, show different amplification values depending on the investigated point. 1D simulations assume the ground conditions can be modelled as axial symmetric ones (both geometric and material). Whenever the preceding assumption is not properly verified 2D simulations must be undertaken. For this reason the present authors performed 2D numerical analyses alongside two representative sections (Fig. 1). The highest amplifications values have been calculated where topographic slopes change or where complex buried geometries are modeled. Seismically-induced rock falls instability. For studying the slope stability of the limestone rocky wall (named MuroMurato), a survey of the falls or likely to fall rocky boulders has been undertaken. Thus, the study at the first step focused on the geometric characteristics of the rocky blocks and the downwards kinematic energy associated to the rolling and falling Fig. 2 – Localization of the most important amplifications drawn from 1D and 2D numerical analyses.