1,721,091 research outputs found
Influenza della granulometria, della densità e della modalità di preparazione sulla ritenzione idrica degli inerti di Stava
No full textL’articolo presenta i risultati di una campagna di prove di laboratorio effettuata su sterili minerari (tailings) al fine di analizzarne il comportamento idraulico in condizioni non sature. Per una corretta progettazione e analisi di stabilità dei bacini di decantazione realistiche, un’approfondita caratterizzazione geotecnica dei materiali riveste infatti un ruolo fondamentale. Le prove, condotte presso il Laboratorio Geotecnico del Politecnico di Torino, sono state effettuate su sterili fuoriusciti in seguito al collasso dei due bacini della miniera di Stava (Italia) occorsa nel 1985. Il comportamento idraulico in condizioni non sature è stato studiato mediante prove nelle quali la suzione era imposta ed il contenuto d’acqua misurato (tecnica della traslazione degli assi e dell’equilibrio di vapore) e prove nelle quali il contenuto d’acqua era imposto e la suzione misurata (tecnica del punto di rugiada). Al fine di considerare l’eterogeneità del materiale deposto in sito, è stata studiata la dipendenza della ritenzione idraulica (WRC) dalla distribuzione granulometrica, dalle tecniche di preparazione del campione e dal suo indice dei vuoti iniziale
Static liquefaction response of silty tailings in nearly saturated conditions
No full textTailing storage facilities are complex geotechnical systems characterized by a wide surface exposed to the atmosphere whose interaction governs the position of the water table within the basin, and so the extension of the unsaturated zone above the phreatic surface. A detailed knowledge of the hydro-mechanical response of the tailings is fundamental to reliably assess the stability of the tailing dams to exclude the onset of static liquefaction which has been recognized as one of the major causes of dam failure.
This research gives the main overcomes of an experimental campaign to study the static liquefaction behaviour of silty tailings collected after the failure of the Stava basins. Monotonic triaxial tests were performed to investigate the static liquefaction response of tailings in nearly saturated conditions in terms of stress-strain behaviour. The dependency of the static liquefaction strength on the sample preparation technique, the void ratio and the degree of saturation was investigated. The degree of saturation and the sample preparation method were proved to affect their static liquefaction strength while, upon certain values, the initial density was not the main factor affecting the hydro-mechanical behaviour of tailings under investigation. Some theoretical relationships between the –B Skempton parameter and the degree of saturation with the respective experimental values were also compared. The experimental data collected in the present research during the saturation phase of the sample were in good agreement with the theoretical formulations proposed by Reuss and with those given by Lade and Hernandez. The Critical State Line (CSL) of the nearly saturated Stava tailings was successfully compared with those obtained by the same soil in saturated conditions
STUDIO SPERIMENTALE DELLE RELAZIONI TRA IL PARAMETRO-B DI SKEMPTON E IL GRADO DI SATURAZIONE DEGLI INERTI DI STAVA IN CONDIZIONI NON SATURE E PROSSIME ALLA SATURAZIONE
No full textLa nota presenta i risultati di una campagna di prove sperimentali realizzata presso il Laboratorio Geotecnico del Politecnico di Torino su materiali di risulta di coltivazioni minerarie (tailings) in condizioni non sature e prossime alla saturazione. Ai fini di ottenere una stima attendibile del grado di saturazione a partire dal valore del parametro-B di Skempton, il presente studio analizza differenti relazioni teoriche tra le due grandezze, confrontandole quindi con i valori sperimentali del parametro-B misurato in cella triassiale ed il grado di saturazione valutato a ritroso
Water retention response of unsaturated Stava tailings
No full textTailing dams are geotechnical structures with a pronounced surface interaction with the atmosphere which leads to a large portion of material in unsaturated conditions. Due to the hydro - mechanical coupling, an accurate prediction of the hydraulic behaviour within the unsaturated layers has a significant effect on the mechanical behaviour, particularly in terms of the stability of tailing dams both during mining activities and after operations cease.
This research provides the results of an investigation on the hydraulic behaviour of tailings collected from the Stava basins. The hydraulic response was studied by means of water retention tests where the suction was imposed and the water content was monitored, and tests where the water content was imposed and the suction was measured with psychrometer. The dependency of the water retention relationship on the particle sorting, the preparation technique and on the initial void ratio was studied to account for the in-situ heterogeneity of tailings. Looser specimens showed a lower water retention behaviour than that denser specimens. Similarly, the decrease of the fine content was demonstrated to reduce the water retention capability. Slurry Stava tailings reveal higher retention capability than the statically compacted samples, thus confirming the importance of the preparation technique in determining their hydro - mechanical response as previously demonstrated for standard soils
Evaluation of Stress and Strain Induced by the Rock Compaction on a Hydrocarbon Well Completion Using Contact Interfaces with Abaqus
No full textStoccaggio di CO2 nel sottosuolo: determinazione della pressione capillare di soglia col metodo residuo
Full text linkSome remarks on single- and double-porosity modeling of coupled chemo-hydro-mechanical processes in clays
Full text linkActive clays are known to possess an aggregated structure, which justifies the use of double-porosity models to reproduce their behavior. Simulation of chemo-mechanical processes requires instead the introduction of a relevant number of coupled mechanical and transport laws. It follows that double porosity models for coupled chemo-hydro-mechanical require a relevant number of parameters, which are twice those needed by single porosity models. The aim of this work is to evaluate the consequences of using single- and double-porosity frameworks to simulate the transient chemo-mechanical processes in active clays, showing how models based on simple microstructural considerations can help in performing simulations which are a reasonable trade-off between simplicity and accuracy. In particular with single porosity models, it might be necessary introducing parameters having a doubtful meaning to describe adsorption-desorption processes. This type of assumption is not required by double porosity models. While for compacted clays these conclusions are corroborated with microstructural observations, the same hold also when reproducing the behavior of an active clay at a remolded condition. In this latter case the delay of swelling with respect to desalinization, typical of remolded conditions, was satisfactorily reproduced only with double porosity models
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