An excavator is in-fact a perfect drilling rig. With it's crawler base and hydraulic powered system. these two factors made it a good candidate to be converted into a versatile and self mobile drilling rig.
And as a drilling rig, it can be used to drill holes for piles and a well known application will be bored piles and micropiles. The drill head is powered by the on board hydraulic system with out much or major modification required.
The use of an excavator modified to drill micropiles has another advantage and this is the ability of the same machine to lift the micropile reinforcement and place it into the drilled hole before grouting. Thus this dispense the need of a second crane.
By the way we mentioned micropiles and these are use as foundation known as micropiles foundation. Below is a picture of a drilling rig modified from an excavator.
The above picture shows an excavator modified for drilling micropiles. Rather heavy duty and not likely to be used in a house backyard.
