1,721,135 research outputs found
Metodo di rilevazione di elementi solidi trascinati da una correntedi un alveo di un corso d'acqua e dispositivo di rilevazione relativo
No full textUncertainty propagation using some common mixing rules for the modelling and interpretation of electromagnetic data
No full textThis study deals with the calculation of the uncertainty that occurs when one wants to estimate the porosity of a mixture from its electric and electromagnetic response. The uncertainty when estimating the electric and/or electromagnetic response (conductivity, permittivity or magnetic permeability) of a saturated granular medium, from the responses of its components has also been calculated. Some of the most common mixing rules used in geophysics have been analysed. Particular attention has been paid to the uncertainties that can be encountered in field surveys in order to make the user aware of the range of variability of the results. A comparative analysis shows that in the porosity range (10% < ϕ <25%), some commonly used mixing rules can lead to results that differ by even 100%. In the same porosity range, when uncertainty bars are considered, some mixing rules show such overlapped uncertainty bands that the choice among different mixing rules seems to depend more on the achievable uncertainty than the physical hypotheses on which they are built. In fully saturated materials, such as in river bed sediments or in the saturated zone of aquifers, the estimation of the water content can easily be affected by an uncertainty of 10%. Particular attention should therefore be paid when dealing with multi-phase materials: the Archie mixing rule, for example, when applied to low saturated, loose material, may give rise to high uncertaintie
Erratum: Uncertainty propagation using some common mixing rules for the modelling and interpretation of electromagnetic data (Near Surface Geophysics (2009) 7: 4 (297))
No full textTheoretical Derivation of a Peak Particle Velocity-Distance Law for the Prediction of Vibrations from Blasting
No full textI would like to suggest a theoretical justification for the mathematical structure of some laws for predicting the maximum particle velocity vibration from blasting operations in the light of some basic notions of elastic and anelastic wave theory. Within this point of view, in dimensionally correct expressions, the terms pertaining to the rock, to the blast and to the seismic wave become evident and recognisable. A law is presented that can be used to forecast the maximum particle velocity on the basis of some blast design and rock parameters. Four tests of the proposed law performed with real data sets seem to confirm fairly well its reliabilit
A geophone apparatus having an increased sensitivity to horizontally polarized shear waves
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Estimation of thin fracture aperture in a marble block by GPR sounding
No full textIn order to optimize the cutting of the marble blocks to be used in the restoration of the dome of the Holy Shroud Chapel of Turin cathedral, some GPR tests have been done in a laboratory to detect thin fractures in a marble block. We made some preliminary measurements to estimate the GPR wave velocity in an intact block and to calculate the permittivity of the marble. Then, the block was cut and GPR measurements with different fracture fillings and fracture apertures were performed. The results demonstrate that with at 2 GHz in antenna a fracture, a millimeter open, can be detected. An analysis carried out on the experimental reflection coefficients with the thin layer theory, allowed us to estimate the different fracture apertures. We found the possibility of estimating fracture apertures ranging from 1/10 to 1/5 of the wavelength at 2 GHz in air. The phase and the amplitude of the reflected signals with different fillings demonstrated the possibility of detecting thin fractures and discriminating between dry- or water -saturated filling
Case study: A GPR survey on a morainic lake in northern Italy for bathymetry, water volume and sediment characterization
Full text linkWe carried out an extensive waterborne GPR survey consisting of 50 profiles with a total length of nearly
37 km on the morainic lake of Candia northerly Turin (Italy). Our aim was to test the capability of GPR to estimate
the bathymetry, the water volume and the sediment type. We enhanced and controlled the GPR data
processing and interpretation with bathymetry acquired with an acoustic echo sounder and measured conductivity
and temperature profile of the water column with a multiparametric probe. We also analyzed the
diffraction hyperbola that originated within the sediments in order to estimate the velocity and relative permittivity.
With the permittivity and dielectric mixing rules, we estimated the porosity of the sediments above
the diffracting objects and drew a map of the bottom lake porosity
Fast ERT to estimate pollutants and solid transport in water flow: a laboratory experiment
No full textThe understanding and evaluation of the phenomena related to pollutants diffusion, solid transport or lithic material deposition within a river have a prominent role in hydraulics and fluvial geomorphology. In this respect, the direct measurement of the amount of transported material is certainly one of the most difficult tasks in the field of river hydraulics due to the heterogeneity and representativeness of the samples. In this paper, we investigate the applicability of a very fast (about ten seconds or less), non-invasive electrical resistivity tomography to identify and estimate pollutant and solid transport variations in a fast water flow. To do this, three experimental tests, in a laboratory channel with a flow rate of 0.5 m/s, are presented using both a pollutant flow and different types of solid transport (fine and coarse sands). Data are interpreted by means of classical models that relate the variation in electric conductivity to variations in concentration or in volume fraction of suspended material. Whereas the identification and positioning of the pollutant or solid transport is successful, the estimation of governing parameters still remains mainly qualitativ
Applicazione del georadar nel campo dei controlli non-distruttivi ed in campo geologico-tecnico
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