The old iron mines of the North-West of France have geometrical and exploitation configurations appreciably similar, with dips varying between 30° and 90°. Within the framework of the establishment of risk maps related to these exploitations, the observation of subsidence in certain basins leds us to try to better know the conditions of occurrence and the consequences on the surface of these phenomena, and in particular the influence of the dip on their relevance. A modeling was thus undertaken, consisting initially of back-analysis of a subsidence trough observed and studied, in order to seek the initiating mechanism within mining work and to appreciate the influence and the degree of reliability of the parameters, and in the second time the parameterised analysis of the zones of potential failure according to the dip, the opening of the mine seam, the extraction ratio and the thickness of the overburden. The contribution of this modeling and the experience feedback of other mining basins allowed to fix the principles of evaluation of the subsidence alea, in terms of intensity and occurrence, of these deposits.