Several models were proposed in the literature for the extremely complex process of ground freezing, characterized by the migration of water from the underground water table to the freezing front. The consequence is that frozen soil is pushed upwards (heaving). These models can roughly be grouped in two categories: the ones with a sharp interface between frozen and unfrozen regions (sometimes called of primary type), and the models in which ice formation occurs across a thin layer hosting a complex of thermodynamical processes (secondary type models). The present paper illustrates the general principles of primary frost heave models, making a comparison among various models, pointing out some inconsistency contained in some of them, and presenting the set of equations which are believed to describe the phenomenon in the correct way, once the basic assumptions on the behaviour of the system are stated. The one-dimensional case is examined in detail, and the explicit solutions of the quasi-steady approximation are studied, emphasizing the conditions under which the forcing ice can break the soil producing layers of pure ice (ice lensing).