Once hard rock formations are encountered or there is a need to socket the bored piles into rock foundations due to design requirement, than the drilling will need to use tools geared for rock drilling.
Rock Auger With Bullet Teeths
As rocks have different hardness, thus drilling tools can be adapted to drill in different degree of hardness. As an example, the versatile auger can be modified and installed with bullet teeth with replaceable bullet style carbide teeth turning it into a rock auger.
Bullet Teeth with Holder
Rock augers are used under dry drilling conditions when the drilled bored pile hole is dry. However there are times when the drilling is under fluid used to stabilization fluid. In this case, the drilling in rock will make use of rock boring bucket. The purpose of using bucket is to allow the drilled materials to be collected into the bucket and disposed off.
Rock Boring Bucket
When the drilling hits very hard rocks like granites, than the drilling tools are changed. There are 3 ways to drill in very hard rocks. In dry or semi-dry conditions the drilling can make use of down the hole hammers. DTHH comes in various sizes from 100mm to 600mm. For large diameter piles ie 1m and above, DTHH can be maneuver around to achieve the required diameter.
Chisel for Rocks
When DTHH can’t be used, then the piling contractor can have the options of using chisels or coring bucket. Chisels are large heavy rectangular object with a sharpened. The chisel is lifted above the rock level to a certain height and allows it to free fall thus slowly chiseling or pounding away at the rock level. Effectiveness of this method depends on the mass, cutting tip of the chisel. The rest is the job of gravity.
Coring Bucket
The next tool is coring bucket.This tool has bullet teeth with replaceable bullet style carbide teeth arranged in a circular pattern in various diameters. Through the weight and circular action of the boring rig, the coring bucket slowly cored into the rocks. The working principle is like the cement coring. However the coring process may fractured the rock into pieces, these loose pieces are picked up using cleaning or boring bucket. As coring is under the stabilization fluid, the fluid acts as a coolant and lubricant during the coring process.
Coring Barell
The availability of tools depends on the piling or foundation contractors. An experience and established foundation contractors will have all the above tools and more at their disposal to counter any types of geological conditions.