Simulating the overturning of mobile crane caused by punching failure of ground

This study focuses on instability of ground affecting the overturning of mobile cranes. The mobile crane is a truck comprising machinery for hoisting equipment. The mobile crane is usually kept level during the hoisting operations by supported from four outriggers, which are located at each comer. When the outriggers penetrate due to failure of the ground, however, the crane becomes unstable. Model tests using a 1/20-scale model mobile crane were carried out in a centrifuge to investigate the interrelationship between failure characteristics of the ground and instability of the mobile crane, ensuring equivalence of pressure on the outrigger between prototype and model. It was found that the mobile crane became unstable due to rapid penetration of the outriggers caused by brittle failure of the ground. Back-analysis of experimental records was undertaken to ascertain the kinetic conditions for overturning, and this shows that mobile cranes can fail due to kinematic conditions where rapid penetration occurs, prior to reaching the limiting static equilibrium. This result indicates the need to classify stability of mobile cranes according to specific ground conditions.