Abstract: A series of high-strength silicon powder mortar material model specimens with single joint which containing the specific size and the particular inclination are made in the laboratory, the failure modes and characteristics of the single jointed specimens are researched by means of the conventional triaxial compression test. Three typical cracks are observed during the test; they are stretching mode crack (Ⅰ), sliding mode crack (Ⅱ), tearing mode crack (Ⅲ). Ⅱ, Ⅲ cracks are ubiquitous and Ⅰcrack is only local existing. The main failure modes are X-shaped shear failure; and the pure shear failure mode is found under specific conditions. The results show that: the expanding regularity of fault cracks has close ties with the preexisting fissures; the confining pressure is the main influencing factors that the failure modes of the single jointed specimens under the conventional triaxial compression test; the preexisting length mainly affect the size of the fracture extension and joint inclination is the cause of the crack initiation.

Key words: rock mechanics, model material, conventional triaxial compression test, failure characteristic, tearing mode crack