1,721,180 research outputs found
Session report: Geophysics,1
Full text linkA large number of papers has been presented in the session devoted to geophysical methods, confirming their consolidated role in site characterization. Different applications and a wide variety of techniques are also discussed in the present report. For one the reliability, which can be improved with advanced interpretation strategies based on joint inversion of multiple geophysical datasets. The role of guidelines for the execution and interpretation in improving the standard of practice is finally commente
Determinazione delle Proprietà’ Dinamiche dei Terreni Mediante l’Uso di Onde Superficiali
No full textDeformation of landfill from measurements of shear wave velocity and damping - Discussion
Full text linkThe author presents a method for using in-situ seismic test results to estimate the short-term deformations of geomaterials. The effort to introduce rational algorithms for the evaluation of settlements of shallow foundations on the basis of measured physical quantities is noteworthy, considering that current geotechnical design, especially on small-scale projects, is often based on empirical correlations between
settlements and penetration test results that rarely reflect the actual site conditions. In this context the development of simple procedures based on the results of relatively inexpensive in-situ tests including seismic tests is of paramount importance.
Nevertheless it is important to account properly for the physics of wave propagation when inferring material parameters from seismic test results. In this respect, the writers would like to make some observations related to the methods used to evaluate the shear wave velocity and material
damping ratio of the solid waste from surface wave measurements. This discussion is focused on and restricted to the aspects of the paper related to the use of surface wave methods to estimate the waste properties
A new geostatistical model for shear wave velocity profiles
No full textA consistent procedure is required to deal with uncertainties in seismic hazard studies. In particular, uncertainties in shear wave velocity (VS) profiles are important for 1D numerical simulations of site response conducted within a probabilistic framework. This work proposes a new geostatistical model for shear wave velocity profiles. The main characteristic of the model is the separation of the random variables space and time. The model is calibrated using a database of surface wave tests compiled for this purpose. The flexibility of the model is then demonstrated by presenting a first prototype version for down-hole tests. The proposed geostatistical model is validated through an application to a real case study at Mirandola (Italy), one of the sites included in the InterPACIFIC project. The results show a significant improvement in the management (i.e., treatment) of uncertainties for ground response analyses, compared to the methods usually adopted for this purpose. The new geostatistical model allows for a rigorous quantification of the uncertainties introduced in the hazard study; these uncertainties depend on both the characteristics of the investigated site and the performed test. It is also shown that the randomization procedure provides a set of profiles which are fully consistent with the independent experimental “site signatures” available at the site
Porosity of Fluid-Saturated Porous Media from Measured Seismic Wave Velocities
No full textThis paper presents a novel procedure for determining
porosity in fluid-saturated porous media from measured
shear and dilatational wave velocities. The method is
developed using the theory of linear poroelasticity in the
low-frequency limit, which is equivalent to considering
the fluid-saturated porous medium as a closed (undrained)
system with the pore fluid moving in phase with
the soil skeleton. The new procedure for the in-situ measurement
of porosity has been applied at two sites in Italy
using cross-hole seismic data. The results obtained are in
excellent agreement with independent laboratory data
gathered from undisturbed soil specimens
Joint inversion of seismic and electrical data in saturated porous media
Full text linkJoint inversion strategies and physical constraints on model parameters may be used to mitigate equivalence problems caused by solution non-uniqueness. This strategy is quite a common practice in exploration geophysics, where dedicated rock physical studies are usually carried out, while it is not so frequent in near surface geophysics. We use porosity as a constraint among seismic wave velocities and electrical resistivity in a deterministic joint inversion algorithm for surface wave dispersion, P-wave traveltimes and apparent resistivity from vertical electrical sounding. These data are often available for near surface characterization. We show that the physical constraint among model parameters leads to internally consistent geophysical models in which solution non-uniqueness is mitigated. Moreover, an estimate of soil porosity is obtained as a relevant side product of the procedure. In particular, we consider a clean sand deposit and hence the appropriate formulations for the computation of porosity from seismic velocities and resistivity are implemented in the algorithm. We first demonstrate how the non-uniqueness of the solution is reduced in a synthetic case and then we applied the algorithm to a real-case study. The algorithm is here developed for one-dimensional condition and for granular soils to better investigate the physical constraint only, but it can be extended to the two-dimensional or three-dimensional case as well as to other materials with the adoption of proper rock physical relationships
Assessment of the seismic risk associated with small earth dams: a simplified approach
Full text linkSmall earth dams are characterized by a reduced height of the retaining structure and by a limited reservoir volume of water. They are often located along slopes close to populated areas, therefore the risk associated with their potential rupture could be considerable. Also for this reason, the evaluation of their seismic vulnerability is of paramount importance for Civil Protection purposes. In addition, the usual lack of technical information represents a significant further challenge. In this regards, a simplified methodology based on a reduced number of parameters was required for vulnerability assessment studies. A simplified procedure was developed to systematically classify a large number of small earth dams. The proposed methodology is based on the compilation of data-sheets that lead to a preliminary classification of structures in terms of their associated seismic risk. The application of this procedure to about a hundred earth dams in the Piedmont region allowed
identifying the most critical structures, which require a priority in the planning of further investigations and analyses
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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