It is hardly possible to find a single rheological law for all the soils. However they have mechanical properties (elasticity,plasticity,creep,damage etc. ) that are met in some special sciences, and basic equations of these disciplines can be applied to earth structures. This way is taken in this book. It represents the results that can be used as a base for computations in many fields of the Geomechanics in its wide sense. Deformation and fracture of many objects include a row of important effects that must be taken into account. Some of them can be considered in the rheological law that, however, must be simple enough to solve the problems for real objects. On the base of experiments and some theoretical investigations the constitutive equations that take into account large strains, a non-linear unsteady creep, an influence of a stress state type, an initial anisotropy and a damage are introduced.