The changes of engineering-geological conditions occurring during the construction and operation of buildings and structures are considered. Engineering-geological surveys and studies to justify repair and reconstruction projects, which must take into account such changes, is a separate section of engineering geology.

The strength of clay rocks is largely determined by their water content and the proportions of its various categories. At present, most authors consider water categories from the standpoint of their formation under the influence of the energy field of the clay particle. It is known that the intensity of any energy field decreases approximately exponentially, and therefore the transition of water from one category to another is gradual and smooth. When the particle field is superimposed on water, its structure is distorted as a result of changes in the character of the translational motion of water molecules.