The following narrative and images capture a selection of the most commonly used plant operating on earthworks construction projects at the present time. It expands on the text by Horner (1988), which was included in the first edition of this book, and Dumelow (2012). The details given for specific items of plant are typical only and for more accurate descriptions manufacturers’ websites should be consulted.
Backacters comprise a bucket on the end of an articulated boom, set on a pneumatic-tyred or crawler tractor unit. The boom, bucket arm and bucket are usually controlled by hydraulic rams. They operate by digging towards the machine in an arc from a small distance above the surface on which the machine stands to a position vertically below the outer edge of the machine. Loading is generally carried out by lifting the bucket, and swinging the boom away from the working face to the awaiting haulage vehicle. Alternatively, material can be dumped adjacent to the machine.
