  The description of the early stage of microfracture growth in a quasibrittle
solid with thermodynamic positions is considered. From the most general
thermodynamic performances the "principle" of minimization of free energy is
received. The account high (down to thirds) degrees in expansion of free energy
concerning parameters of a mechanical field and average microcrack energy has
allowed to write down the state equation for solids with microcracks, to find
equilibrium and nonequilibrium values of their average energy. From positions
of a developed formalism the reason of high stability of work developments on
small depths and mechanism of loss of their stability on the large depths is
explained. From the fact of presence of qualitatively various behaviour of a
material on the large depths the additional estimated connection between
parameters of the theory is established.
