The analysis of comparative digital photographs by Particle Image Velocimetry (PIV) offers a powerful technique for the demonstration of deformation mechanisms in soil models. Where small-scale models can be tested in a geotechnical centrifuge at a sufficiently uniform acceleration to broadly recreate full-scale stresses, it will follow that soil stiffness and strength will equally be appropriate to the full scale. If sufficient attention has been paid to the creation of appropriate boundary conditions, and to the actuation of a representative construction and loading sequence, the observed mechanism can be used to deduce the characteristic features of similar processes in the field. This requires a further step of simplification and mathematical characterization. Any recommendation for the use of such a mechanism in design should depend on a consistency check of the conservation of energy in the model, leading to sufficiently accurate predictions at model scale. Such a demonstration is consistent with the Mobilizable Strength Design (MSD) method which has been shown to serve as an efficient means of predicting and controlling ground deformations. Examples will be given of the behavior of tunnels, deep excavations and slopes.