GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 Let us consider a simple vertcal strain model, made up of overlying layers (e.g., RS, LAB, etc.) in the consolidaton phase. According to such a model, the subsidence velocity (or cumulated displacement in a given tme interval) at a point is given by sum of contributons by the N layers under such point. Denotng by v such velocity value and by h j the thickness of the j-th layer, then: , (1) where C j are constants depending on the mechanical propertes of the considered layers, which can be viewed as the contributon provided by each thickness unit (e.g., 1 m) of layer. If for M wells the thicknesses h j are known, we have M equatons like (1) in which v and h j are known. Then, the constants C j can be calculated by means of multvariate statstcal analysis, e.g., by adoptng a Least Squares or a Maximum Likelihood approach. Once C j values have been evaluated, the thickness of shallow lithologies can be calculated for whatever point of the study area. This may provide a promising powerful method of geotechnical characterizaton at urban scale and at a relatvely low cost. This model may also be adapted to study variatons in subsidence velocity over tme, according to a mult-layer Terzaghi consolidaton model. In this case, Eq. 1 would be nonlinear and, therefore, the analysis would follow a nonlinear multvariate approach. Conclusion ● The A-DInSAR post-seismic data, recorded in the tme range 2010-2021, revealed a subsidence phenomenon, stll ongoing, due to the concurring efect of variaton in pore pressures and secondary consolidaton of shallow and deep rocks. The correlaton analysis and the evidence illustrated in Fig. 3d allow us to conclude that subsidence velocites are mainly controlled by the propertes and thicknesses of shallower rock layers, such as RS and LAB. ● The cross-correlaton analysis highlighted a signifcant correlaton between seasonal fuctuatons in subsidence rate and rainfall variatons. ● The seasonally adjusted A-DInSAR tme series highlighted an anomaly in the subsidence trend, observable during the Amatrice-Norcia seismic sequence of 2016. The study of this anomaly deserves atenton and will be the subject of future research. ● Ground deformatons detected by means of A-DInSAR technology may provide a promising inversion criterion, enabling us to perform a geotechnical characterizaton of shallow rock layers, over large areas, at relatvely low costs. References v = N ∑ j =1 C j ∙ h j