Abstract: In order to explain the failure and breakage mechanisms of structural geological materials, the plane strain compression tests of the samples of prismatic structural bodies assembled in two different patterns are conducted under different confining stresses. During the breaking process of structural bodies, it is found experimentally that the main failure modes of structural bodies are splitting, shear failure and crushing, but finally the breakage bands form; while the confining stress increases, strain softening gradually turns to be strain hardening; when the lateral stress is low, strain softening and volume expansion and lateral extrusion can be observed; however, when the lateral stress is high, strain hardening, volume contraction and lateral contraction become prevalent; whatever the confining stress is and which pattern the structural bodies are assembled by, the rotation of the structural bodies is hardly observed.

Key words: prismatic structural bodies, plane strain compression tests, breaking process, breakage bands