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What do you mean by Drillability?
Drillability can be defined as the ability of the rock to be drilled or bored. Drillability considers the influence that. intact rock properties, breakability and abrasivity, have during drilling and boring in hard rock.
What is Drillability index?
THE DRILLABILITY INDEX IS BASED ON THE PENETRATION RATE ACHIEVED BY A 3/4-INCH DIAMETER BIT DRILLING A HOLE 4 INCHES DEEP. A ROCK ABRASIVE INDEX IS ALSO PROPOSED, AND IS BASED ON THE CHANGE IN AREA OF THE BIT CUTTING-EDGE PROFILE. DRILLABILITY AND ABRASIVE INDICES HAVE BEEN DETERMINED FOR 98 ROCK TYPES.
What is drilling index?
Drilling rate index (DRI) is a measure of hardness or ease of rock drillability. DRI is determined according to suggested method developed at the Engineering Geology Laboratory of the Norwegian Institute of Technology (NTNU) of the University of Trondheim.
Can you drill a hole without a drill?
You can use rods and tubes with friction to create heat to make a hole without a drill-bit. Cutting holes with friction can even give better holes. Take a battery-operated, portable electric drill or a small stand drill and put a piece of dowel rod of 4-8mm in diameter into the chuck.
Why is the drillability of a rock important?
The drillability is actually just a normalized rate of penetration, which is low in a hard rock it and high in a soft rock because of the high drilling rate. It can be used as a log because it inherently tells us something about the properties of the rock that we drill.
What is the radius of an increase in drillability?
The region of changed rock properties (increased drillability) is defined as a radius of 6.4 m. Inside this region, the rock is more drillable and the bit goes in the direction of least resistance.
How does the drillability of a rock affect cutter life?
The final gradient (−)m can be modified by the abrasiveness of the rock, which is based on a normalized value of CLI (see www.drillability.com ). Values less than 20 rapidly reduce cutter life, and values over 20 tend to increase cutter life.
Which is a reliable indicator of drill bit wear?
Parameter for drill bitwear. It depends on the mineral composition in the rock. Quartz(SiO2) content is usually a reliable indicator of drill bit wear. % silica content: 10 – 20 Non abrasive, 20 – 40 Abrasive, >40 Very abrasive. Rock type. Quartz Content %. Amphibolite.