| Joint cracks often play an important role in controlling the mechanical properties of rock mass.The damage of single-tooth in shearing process is the failure for basic unit of shear failure of joints.This paper studies the theoretical formula of shearing strength based on a regular single-tooth joint model and the theoretical formula is verified by the indoor shear test data.The main results are as follows:1)Shear failure mode of rock joints is summarized at first.According to the damage degree between the upper and lower joint surfaces,there are mainly two damage models:wearing failure and shearing failure.For shearing failure,the shearing process must go through two stages of climbing and shearing.Therefore,it can be conclude that the climbing and shearing phenomena constitute the shear failure process of regular single-tooth joints.2)Taking the regular single-tooth shear failure process as the analysis object,the stress of the single-tooth surface during the shearing process is analyzed from the dynamic point of view,and the relationship between shear strength of the single-tooth joint model and the climbing displacement ds,the normal stress σ3,the characteristic value of horizontal stress,the undulating angle a,and the friction coefficient f along the joint surface,is deduced based on the functional relationship and the theory of limit equilibrium.3)According to the results of joint shear test,three aspects of the theoretical formula are studied:a.Discuss the regularity of the formula and find that there is a positive correlation between the shear strength r and the normal stress σ3,the undulating angle a,and the friction coefficient f.b.By comparing the experimental values of the shear strength with the calculated values obtained from the theoretical formula,the relationship of 10 times between the experimental value and the calculated value is concluded and the theoretical formula is corrected.So a modified shear strength theory formula of single-tooth joint is proposed.a.Comparing shear strength from modified theoretical formula,Ladanyi&Archambault formula and Patton formula,it is found that when using the theoretical formula proposed in this paper to estimate the shear strength of joint,the error is minimal and is distributed within 20%. |
