Fracture mechanics of mining dragline booms

Mining draglines are large mining machines which have a booms of about 100 m in length. The booms are tubular structures made up of three large chords connected by smaller lacing tubes. There is a regular cracking phenomenon at the welds which means that the cracking must be remotely detected, exactly located and repaired. This paper describes the cracks which grow in the welds joints (called clusters) and the system by which the booms are protected from catastrophic collapse and the maintenance and repair techniques used to keep them in service.