Study of shear strength characteristics of simulation rock structural planes based on multi-size direct shear tests

It has important value of theory and practical significance to understand the mechanical characteristics of rock structural planes by taking direct shear tests for shear strength of simulation rock structural planes with different sizes (especially large sizes). Based on MSJ-DST, the direct shear tests of simulation rock structural planes in sizes 20 cmx20 cm, 40 cmx40 cm, 60 cmx60 cm, 80 cmx80 cm and 100 cmx100 cm are taken under the normal stresses from 200 kPa to 1 000 kPa. Then, the characteristics of shear strength of rock structural planes with different sizes are studied. The results indicate that the stresses and deformation characteristics of simulation rock structural planes under different normal stresses are similar; and the peak shear displacements are generally fluctuated in the vicinity of a certain value. Under the same normal stress, the peak shear strength values of simulation rock structural planes with different sizes are fluctuated in the vicinity of a certain value; and the residual shear strength values rise slightly as the size increases. Under five grade normal stresses, the variations of peak shear strength and residual shear strength with different sizes are approximately same; and the ratio of residual shear strength value and peak shear strength value increases and tends to be stable as normal stress increases.