NUMERICAL SIMULATION OF THE END FRICTIONAL EFFECT OF ROCK SPECIMENS

The end frictional effect of a specimen can influence the plastic equivalent strain, lateral displacement and element stress-strain curve in the specimen. This paper presents gradual change forms on plastic equivalent strain and lateral displacement in various frictional coefficients, which are obtained from the simulation of the influence of the end frictional effect on a plastic equivalent strain, lateral displacement and element stress-strain curve in a plane strain using contact element in ANSYS. When friction is the minimum on the contact plane, the plot of plastic equivalent strain is two X-shaped localization bands from the upper to the lower end with a uniform distribution of lateral displacement. When friction is large on the contact plane, the plastic equivalent strain localization bands increase greatly and move towards the middle of the specimen. At the same time, the lateral displacement distribution is not uniform and the displacement in the middle is larger than those near the two ends. When the lateral displacement is restricted at both ends of the specimen, i.e., the friction is very large, the plot of plastic equivalent strain change to one X-shaped localization band, the lateral displacement distribution becomes even less uniform, and large dilation occur in the middle of the specimen.