1,721,031 research outputs found
Previsione probabilistica dei tempi e dei costi di scavo di gallerie in masse rocciose con eterogeneità localizzate
No full textCaratteristiche Geomeccaniche delle Rocce e Scavo di Gallerie: Sintesi dei Dati Raccolti in Varie Realizzazioni
No full textMonitoring Mining Subsidence During Backfill Operations in the Old Mine of Masua – Acquaresi
No full textImprovement of Disc Cutter Performance by Water Jet Assistance
No full textAbstract This article deals with the problem of assisting
disc cutters by means of high-velocity jets of water, with
the aim of increasing the excavation rate while improving
the working conditions, with particular reference to wear.
The results of an experimental research undertaken at the
Waterjet Laboratory of the University of Cagliari on a
medium–hard abrasive rock clearly show that a higher
removal rate is achieved owing to the weakening action of
a jet directed on one side of the disc, causing deeper
penetration. This outcome is interpreted on the basis of the
scale formation model, which explains why smaller scales
are obtained on the water jet’s side of the groove.
Accordingly, it is suggested that the results can be further
improved if the jet is directed ahead of the tool along the
same path, since, in this way, larger scales can be produced
on both sides
Improvement of the excavation performance of PCD drag tools by waterjet assistance
No full textABSTRACT: The possibility of increasing the performance of mechanical tools with the assistance provided by a high-velocity water jet has been explored in the last twenty years. The results of past research have often been controversial and found to vary within a wide range, mainly due to the different experimental conditions adopted. A number of hypotheses have been advanced to explain the variability of the results as well as to disclose the mechanism of water jet assistance. In this paper, after a discussion of the main issues regarding the assistance of mechanical excavation with water jet, the results of an experimental work carried out at the University of Cagliari are illustrated and discussed. The research was aimed both at studying the processes by which mechanical excavation is improved and at quantifying the increment of the excavation performance parameters with water jet.
In particular, the mechanisms involved in the rock-tool-water jet interaction have been studied with the goal of putting into evidence the contribution of the jet both as a way to weaken the rock and to increase the stress leading to scale formation. The better knowledge achieved will be useful for the development of the technology up to a commercial scale
Three-Dimensional Simulation of a Subway Station Segment Comparing the Experimental Results Using Abaqus
No full textLa Subsidenza nelle coltivazioni sub level stoping: il caso della miniera di Acquaresi (Sardegna)
No full textThe article illustrates the study of the subsidence phenomenon occurred in the Acquaresi mine district (South west of Sardinia) and the monitoring program set up for its control. The analysis has been developed on the base of the investigations carried on in the last 15 years together with the aim of the numerical simulation. Two different mechanisms of collapse have been finally individuated: the slipping of the limestone blocks constituting the horizontal pillars of the mine rock structure and the collapse of the vertical walls of the extraction chambers. The system adopted for monitoring the stability evolution of the rock pillars is based on the measurement of the energy released during the slipping process in the form of micro seismic waves. After 5 years, the monitoring system has proved to be suitable for controlling the behaviour of the pillars stability but its reliability has still to be improved
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