Visualization of pile penetration using mechanoluminescent-coated particles

Pile model penetration tests were conducted in a transparent plane strain container filled with granular mechanoluminescent-coated particles. The pile models were constructed with flat- and cone-shaped tips. Load transmission through the analogue granular soil was captured by taking images of the light emissions from one side of the container that were triggered by inter-particle force-induced mechanoluminescence during pile penetration. Time-coincident images were taken from the other side of the container using a second camera and the corresponding displacement fields computed using the digital image correlation method. Particle contact force chains at peak loads are shown to be in reasonable agreement with particle displacement fields. Differences in both displacement fields and patterns of particle contact force chains were detectable between pile models with flat- and cone-shaped pile tips. The orientations of the particle contact force chains generated at the base of the flat-tip pile model at peak pile load were in reasonable agreement with the geometry of the wedge of soil assumed from classical bearing capacity theory.