An excavator is defined as a power-operated digging machine and it includes different types like shovels, draglines, clamshells, backhoes, etc.
A dragline possesses a long jib for digging and dumping and it is used for digging from grade line to great depths below ground.
Its characteristic is that it does not possess positive digging action and lateral control of normal excavators.
A dragline is normally deployed for bulk excavation.
A backhoe is designed primarily for excavation below ground and it is especially employed for trench excavation works.
It digs by forcing the bucket into soils and pulling it towards the machine and it possesses the positive digging action and accurate lateral control.
A shovel is a machine that acts like a man?s digging action with a hand shovel and hence it is called a shovel.
It digs by putting the bucket at the toe of excavation and pulling it up.
Though a shovel has limited ability to dig below ground level, it is very efficient in digging above ground like digging an embankment.