The sinkage of tracked vehicles on soft ground

The depth of the rut made by a tracked vehicle when crossing soft ground (the ‘sinkage’) is an index of the difficulty experienced by the vehicle. Sinkage is due to plastic flow of the soil under the imposed stresses and can be related to the shear strength of the soil and the characteristics of the vehicle. Two distinct theories are given, one by Micklethwait and Sherratt based on deductive reasoning, and a simpler inductive method by the author.