METHOD FOR DETERMINING STRAIN-AND-STRESS STATE OF MATERIAL WITH BRITTLE SKELETAL FRAME Russian patent published in 2015 - IPC E21C39/00 G01N3/00 

FIELD: test equipment.

SUBSTANCE: invention relates to test equipment, namely to engineering surveys, and can be used to determine a strain-and-stress state of rocks, and namely to determine a stage of development of deformation processes in mass of material (in rock mass, soils under an engineering facility, etc.). Essence of the invention: specimens of material with a brittle skeletal frame are taken. Loading of specimens is performed and physical and mechanical characteristics of material are recorded, and a stress-deformation curve is built up, as per which parameters characterising a precursor of material destruction are determined. At compression of specimens, coefficients $${\alpha }_p^{-},$$ α_-, α_J are determined, which characterise variation in potential energy of elastic deformation at scattered destruction of material, and the precursor of material destruction is found out by the formula: $$\omega =\alpha \_I_1+{\alpha }_{J}J+{\alpha }_p^{-}\Delta p-{\gamma }^{-},$$ where γ^- - a positive parameter setting a quadratic dependence of surface energy of an accumulated set of microcracks in brittle material, I₁ - relative variation in material volume, J - intensity of tangential deformations, and Δp - variation in intra-threshold pressure.

EFFECT: possibility of characterising a stage of material state prior to destruction, which is a precursor of material destruction, by reducing the time of measurement due to reduction of the number of test specimens.

3 cl, 3 dwg