Abstract:The uniaxial compression strength of marble specimens with diameter of 50 mm increases with their length shortening,but the strength will decrease when soft cushions are used between the specimen ends and loading heads of testing machine. It shows that there is friction at the specimen ends. However the friction effect varies with characteristics of rock. For the two marble blocks of fine crystal with grain size of 0.5~1 mm,the relations of specimen lengths to the uniaxial strength are the same. The strength increases to 130% when the ratio of length to diameter decreases from 2 to 1,and the strength increases to more than 150% when the ratio decreases to 0.6. But the two marble blocks have different strength and Young¢s modulus. The specimen with higher strength has failure crack in cone shape and the other has failure crack in plane. For the marble blocks of coarse crystal with grain size of 5 mm,the influence of their length on the strength is not apparent. The stress-strain curves are very similar after the peak stress of specimens with the ratio of length to diameter smaller than 2.5. For a specimen with diameter of 50 mm and length shorter than 50 mm,the uniaxial compression strength can also be obtained by using soft plastic cushion,which is 0.5 mm in thickness and compressed two times before use. However,as its length gets shorter,the influence of the quality of specimen ends on the strength and Young¢s modulus becomes greater.