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Experimental study on waterjet-assisted percussive rock excavator
Percussive excavating method is used in hard or medium-hard rock formations. This method can be problematic when a large hole needs to be created. One such problem is the reduced lifespan of the drill bit due to uneven abrasion on the blades of percussion tools. If the uneven abrasion on the blades can be reduced, the life of a drill bit can be prolonged, leading to improve excavation rates. Waterjet-assisted rock excavation with percussion tools is expected to reduce the burden on percussion tools and improve the excavation rate. The authors have experimentally studied applications of percussive drills assisted by a water jet to develop an efficient rock excavator for hard rock formations. Two types of excavation are considered. One is working the water jet onto the rock surface where adequate impact beforehand develops cracks in the rock mass, causing hydrodynamic pressure - a so-called 'water wedge' - to appear in the rock mass caused by water invading cracks in the rock mass; then, this hydrodynamic pressure breaks up the rock mass in the direction of the free surfaces. The other is cutting slots on the rock surface first using a water jet to form free surfaces; then dropping bits near the pre-slotted area to break up the rock mass. Experiments showed excavation performance to be improved 2 to 5 times with jet assistance in the first method above. Test data also indicated that slotting the rock surface extensively improved performance in the second method.
Experimental study on waterjet-assisted percussive rock excavator
Percussive excavating method is used in hard or medium-hard rock formations. This method can be problematic when a large hole needs to be created. One such problem is the reduced lifespan of the drill bit due to uneven abrasion on the blades of percussion tools. If the uneven abrasion on the blades can be reduced, the life of a drill bit can be prolonged, leading to improve excavation rates. Waterjet-assisted rock excavation with percussion tools is expected to reduce the burden on percussion tools and improve the excavation rate. The authors have experimentally studied applications of percussive drills assisted by a water jet to develop an efficient rock excavator for hard rock formations. Two types of excavation are considered. One is working the water jet onto the rock surface where adequate impact beforehand develops cracks in the rock mass, causing hydrodynamic pressure - a so-called 'water wedge' - to appear in the rock mass caused by water invading cracks in the rock mass; then, this hydrodynamic pressure breaks up the rock mass in the direction of the free surfaces. The other is cutting slots on the rock surface first using a water jet to form free surfaces; then dropping bits near the pre-slotted area to break up the rock mass. Experiments showed excavation performance to be improved 2 to 5 times with jet assistance in the first method above. Test data also indicated that slotting the rock surface extensively improved performance in the second method.
Experimental study on waterjet-assisted percussive rock excavator
Experimentelle Untersuchung einer wasserstrahlunterstützten Schlagbohr-Steinbruchanlage
Handa, K. (author) / Kiyohashi, H. (author)
2000
4 Seiten, 6 Bilder, 4 Quellen
Conference paper
English
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