Abstract: Experiments were carried out to investigate the marble specimens with medium and coarse grains under conventional triaxial compression by the RMT-150B servo-controlling testing machine. Based on the experimental results, the strength and deformation properties of marble specimens with medium and coarse grains under conventional triaxial compression were studied. The results show that marble will manifest the property of strain softening when the material in the rock does not tend to uniform under the lower confining pressure. However, marble will show the property of plastic flowage when the material deformation becomes uniform under the higher confining pressure. The peak strain of rock material has a positive linear relation with the confining pressure. Although marble specimens with medium grains are different from that with coarse grains, the internal friction coefficient can show the mechanical property of material, and has no distinct relation with the grain size. The sensitivity of residual strength on the confining pressure is higher than that of peak strength.

Key words: rock mechanics, marble, strength, deformation, experimental investigation