Rock Fragmentation by High-Voltage Pulses: Review of Observations and Objectives for the Research
Résumé
The research on the rock-breaking mechanism by electrical discharge began at Tomsk University in the 1960s. Through experiments, Andres (1995) [1] proposed the dependence of the electric breakdown field strength of water, rocks, and oil on the pulse rising time. With a rising time shorter than 500 nanoseconds, the discharge plasma occurs mainly in a sandstone. Otherwise, the discharge occurs in the fluid surrounding it. For a quartzite, this limit is around 200ns, and we know that air is always more conductive than rocks and water. On the ground, after a thunderstorm, especially in deserts of sand, we observe tubes of melted pure silica (Figure 1) composed of Lechatelierite mineral [2]. At the laboratory scale, on rocks, a channel crossing the sample is created. Due to the stress caused by the expansion of the plasma channel, the rock can be fragmented (Figure 2). Several experiments performed to optimize pulse voltage, electrode gap, and the number of pulses will be presented and discussed in the function of the intended applications: drilling hard rocks or rock comminution.
Domaines
Sciences de l'ingénieur [physics]
Origine : Fichiers produits par l'(les) auteur(s)