Grigoryan is a versatile scientist and has enriched modern mechanics and allied branches of science with his outstanding scientific achievements. In the 1960s he developed a mechanical and mathematical theory for the quantitative description of processes of motion, deformation and fracture of soils and rocks, long before similar studies abroad. Under his guidance and with his direct participation, specialists of many organizations have carried out laboratory and field experiments making it possible to specify the material functions and parameters which occur in the general theory and thereby transform it into a tool for specific practical applications. On this basis, in particular, the main problems concerning the effect of powerful explosions in soils and rock, and concerning the force and kinematic action of seismic explosive waves on objects and buildings located in such media, have been formulated and effectively solved. This has been used to ensure the necessary rate of development of both the scientific level of applied studies and technical developments in specialized establishments and departments of the defence complex of the country. His pioneering research played a leading role in this and has been generally recognized.