1,721,029 research outputs found
Shear strength of a pyroclastic unsaturated soil from suction-controlled direct shear tests
No full textHydraulic Behaviour of Unsaturated Pyroclastic Soil Observed at Different Scales
No full textProper soil water retention curves (SWRCs) and hydraulic conductivity functions (HCFs) are necessary for a fair analysis of groundwater flow in unsaturated slopes. In principle SWRC is hysteretic; as a consequence, laboratory characterization may not be sufficient to determine the scanning curve and the hydraulic parameters operating in situ. In this paper some results obtained by tests at different scales (testing on laboratory specimens and physical prototype and measuring in an experimental field) are presented in order to explore the hydraulic behaviour of pyroclastic soils. As regards HCF, in the paper the comparison between the hydraulic conductivity functions obtained from inverse analysis of evaporation lab tests, and the conductivity values estimated on the basis of both in situ measurements and results of tests on the aforementioned physical model is proposed. From these results, the physical prototype size (medium scale) seems to be acceptable for determinations of both SWRC and HC
Monitoraggio di grandezze rilevanti per lo studio dell’innesco di colate di fango in terreni piroclastici
No full textRegime idrico in un pendio di piroclastiti parzialmente sature. Monitoraggio di un sito sperimentale
No full textAN EXPERIMENTAL TECHNIQUE FOR DETERMINING THE HYDRAULIC PROPERTIES OF UNSATURATED PYROCLASTIC SOILS
No full textThe experimental technique proposed in the paper was designed to rapidly and reliably determine both the water retention curve and the permeability function of undisturbed natural pyroclastic soil samples. The technique was developed in the framework of an experimental research project on mudflows in pyroclastic soils in the southern Italian region of Campania (Italy). Grain-size distribution and void ratio of the particular pyroclastic soils suggested investigation of the hydraulic behavior for matric suction values in the range between 0 and 100 kPa. Our experimental technique consisted of a sequence of testing phases to be conducted on a single undisturbed soil sample: A constant head permeation test, a forced evaporation test, and finally a drying test in a pressure plate apparatus. Interpretation of the experimental data was based on inverse modelling and allowed both water retention curves and permeability functions to be determined. The six parameters of the Mualem–van Genuchten model were adopted to describe the hydraulic behavior of the tested soils. Each testing phase supplied experimental data to be used in the interpretation proce- dure: The permeation phase provided a matching data point for the permeability function near saturation; the forced evaporation test was related to the hydraulic behavior for matric suction values ranging from a few kPa to less than 80–90 kPa (i.e., mini-tensiometer functioning range); and the drying steps in the pressure plate apparatus provided information about the retention properties for matric suction values up to 1 MPa. The results shown in the paper clearly confirm the goodness of the experimental design and the interpretation procedure
The hydro-mechanical behaviour of unsaturated pyroclastic soils: An experimental investigation
No full textAn experimental investigation into the hydro-mechanical behaviour of a pyroclastic silty sand was carried out in the framework of a research project on flowslides in pyroclastic soils in the Campania region (Italy). Undisturbed soil samples were taken from the subsoil layers of a test site on a limestone relief mantled by a pyroclastic unsaturated soil cover. The lab investigation was focused on the hydro-mechanical behaviour of a pyroclastic silty sand originated from the Ottaviano eruption of the Somma-Vesuvius volcano some 8000. years ago. The main features of the hydraulic hysteresis domain were evaluated and the matric suction range showing the peak saturation rate with respect to suction was identified using water retention data obtained by means of evaporation and soaking tests. The mechanical behaviour of Ottaviano pozzolana emerged from stress-path controlled triaxial tests on saturated specimens and stress-path and suction controlled triaxial tests on unsaturated specimens. Average soil skeleton stress and matric suction were adopted as stress variables to present and interpret the experimental results. The effects of the unsaturated state on isotropic compressibility and on critical state shear strength are presented and discussed. © 2015 Elsevier B.V.
Caratterizzazione in condizioni di parziale saturazione di una serie stratigrafica di terreni suscettibili di colata di fango
No full textElementi di meccanica dei terreni parzialmente saturi (Collana di Ingegneria Geotecnica)
No full textLa monografia tratta i principi del comportamento idraulico e meccanico dei terreni non saturi, presentando le variabili ed i modelli utili all'inquadramento dei fenomeni in cui tali terreni possono essere coinvolt
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