Rock and Soil Mechanics ›› 2022, Vol. 43 ›› Issue (1): 51-64.doi: 10.16285/j.rsm.2021.5832

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Establishment of constitutive relation of shear deformation for irregular joints in sandstone

CHENG Tan1, GUO Bao-hua1, 2, SUN Jie-hao1, TIAN Shi-xuan1, SUN Chong-xuan1, CHEN Yan1   

  1. 1. School of Energy Science and Engineering, Henan Polytechnic University, Jiaozuo, Henan 454000, China 2. The Collaborative Innovation Center of Coal Safety Production of Henan Province, Henan Polytechnic University, Jiaozuo, Henan 454000, China
  • Online:2022-01-11 Published:2022-03-23
  • Contact: GUO Bao-hua, male, born in 1979, PhD, Professor, research interests: rock fracture deformation and seepage.
  • About author:CHENG Tan, male, born in 1993,,PhD candidate, focusing on rock fracture deformation and seepage.
  • Supported by:
    the National Natural Science Foundation of China (51904092, 52104127), the Fundamental Research Funds for the Universities of Henan Province (NSFRF180336, NSFRF210303), the Natural Science Foundation of Henan (202300410183) and the Key Scientific Research Projects of Colleges and Universities in Henan Province (21A440003).

Abstract: The shear deformation of rock joints is significant for the safety and stability of rock engineering. In order to study the constitutive relation of shear deformation in jointed rock mass under a normal stress, the direct shear tests under different normal stresses were carried out on the sandstone specimens with irregular joints using the RDS-200 rock direct shear test system. Based on the shear stress-deformation curve of the jointed rock, it can be divided into four stages including pre-peak compaction stage, linear stage, yield stage and post-peak softening stage. The post-peak softening stage can be further divided into three types including platform type, gradual decline type and drop type based on the decreasing magnitude and rate of shear stress at the post-peak period. The shear deformation constitutive model of the sandstone with irregular joints was established using piecewise function based on the shear deformation characteristics at different stages. Compared with the existing constitutive models, the new proposed shear deformation constitutive model of the jointed rock mass has a much higher fitting accuracy for the experimental results, which can better describe the deformation characteristics of the jointed rock in the whole shear process. The shear stress-shear displacement curve of irregular joints with different roughness coefficients under different normal stresses can be predicted after determining the relevant model parameters in the corresponding empirical formula after some direct shear tests. The research is practical for understanding the shear deformation of joints in rocks by numerical simulation and the safety evaluation of engineering.

Key words: rock mechanics, rock joints, shear deformation, constitutive relation, empirical formula