基于多尺度直剪试验的岩石模型结构面抗剪强度特征研究

开展岩石模型结构面抗剪强度特征的多尺度（尤其大尺寸）直剪试验研究对于理解岩石结构面力学特性具有重要的理论价值和实践意义。首先，基于多尺度直剪试验仪(MSJ-DST)，对20 cm×20 cm、40 cm×40 cm、60 cm×60 cm、80 cm×80 cm和100 cm×100 cm的岩石模型结构面试样采用法向应力分别为200～1 000 kPa进行直接剪切试验；然后，研究不同尺寸岩石模型结构面抗剪强度的特征。结果表明：不同法向荷载作用下模型的受力变形特点相近，峰值剪切位移总体上随着某一数值附近上下浮动；在同一法向应力作用下，不同尺寸结构面试样的峰值抗剪强度表现出在某一数值附近上下浮动的特征，残余抗剪强度则表现出随尺寸的增加有小幅度增加；5级法向应力作用下，不同尺寸的峰值抗剪强度和残余抗剪强度随着法向应力的变化规律均近似相同，抗剪强度残余值与峰值的比值随着法向应力的增大逐渐增大并趋于稳定。

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 cm×20 cm, 40 cm×40 cm, 60 cm×60 cm, 80 cm×80 cm and 100 cm×100 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.