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| Nonlinear theoretical model for describing shear mechanical behaviors of rock joints |
| SHEN Hui1，2，LIU Yaqun1，2，LIU Bo1，2，LI Haibo1，2，WU Duohua1，2，PENG Bo1，2 |
| (1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. University of Chinese Academy of Sciences，Beijing 100049，China) |
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Abstract Direct shear tests on artificial joint specimens under different normal stress conditions were carried out. Based on the nonlinear characteristics of the experimental results，the linear Goodman shear model was modified，and a nonlinear full-scale shear model was proposed. Most parameters of the model can be obtained from experimental data. The new model can accurately describe the nonlinear relationship between the shear stress and the shear displacement during joint slipping. Referring to the method of determining tangential and normal coupling stiffness coefficients proposed by Saeb and Amadei，a new mathematical formula of the tangential coupling stiffness coefficient，which can describe the nonlinear characteristics of joint slipping，was deduced on the basis of the proposed nonlinear full-scale shear model. A novel incremental shear model was then established. The new model can simultaneously simulate the tangential and normal deformation behaviors of the joints. The incremental shear model was respectively solved by computer programming under the boundary conditions of constant normal load(CNL) and constant normal stiffness(CNS). The results obtained by the nonlinear full-scale model were compared with the available laboratory results，showing an excellent consistency and verifying the suitability and reliability of the proposed full-scale model. Considering both the CNL and CNS boundary conditions，the simulation results of the proposed incremental model were compared with the available laboratory results as well as those of the Saeb-Amadei shear model. The shear stress obtained by the incremental model shows better agreement with the experimental results. It is indicated that the proposed incremental model is more appropriate than the Saeb-Amadei shear model in describing the shearing behaviors of joints. The normal stress and normal displacement calculated by the incremental model are in agreement with the experimental results，indicating the proposed model can generally illustrate the normal mechanical behavior of joint shearing. Therefore，the proposed incremental model can predict both the tangential and normal deformation behaviors of the joints during the shearing process，which verifies the applicability and reliability of the incremental model under different boundary conditions.
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2021, Vol. 40 
