Experimental Study On Shear Characteristics Of Regular Dentate Filling Joint With Series Size

The shear strength of rock joint is an important factor affecting the overall stability of rock mass.It not only has obvious size effect,but also is affected by weak interlayer.At present,the size effect of shear strength of unfilled rock joint has been studied at domestic and abroad,but there are few studies on the size effect of shear strength of regular dentate filling joint.Based on the direct shear test and the analysis of the test results,this paper studies the shear characteristics of regular dentate filling joint with series size under the condition of multiple sets of filling degree and normal stress.The main work and conclusions are as follows :(1)The indoor direct shear tests under multiple sets of filling degree and normal stress conditions were carried out by using the shear strength size effect test system of joint.The results show that the shear stress-shear displacement curves of regular dentate filling joint with series size can be divided into peak curve and sliding curve according to their morphological characteristics.Regardless of the normal stress,the curves of regular dentate filling joint with small filling degree are peak curves,and the curves of regular dentate filling joint with large filling degree are sliding curves.At the same time,under the same normal stress,the peak shear strength of the regular dentate filling joint with different filling degrees does not show obvious size effect.With the increase of filling degree,the peak shear strength,peak shear strength discrete variance and peak normal displacement of the rock joint with different filling degrees gradually decrease,and the corresponding displacement of peak shear strength gradually increases.With the increase of normal stress,the peak shear strength of regular dentate filling joint with the same filling degree does not show obvious size effect,and the peak shear strength,the discrete variance of peak shear strength,the corresponding displacement of peak shear strength and the peak normal displacement of rock joint gradually increase.(2)Based on the DIC equipment and Image-J software,the influence of different conditions on the shear characteristics of the series of regular dentate filling joint was obtained by comparing the test results.The results show that under the same normal stress,with the increase of filling degree,the high strain area of series of regular dentate filling joint shifts from the rock joint to the weak interlayer,and the density of the high strain area gradually increases.The degree of damage on the surface of the rock joint gradually decreases,and the proportion of shear damage area gradually decreases.With the increase of normal stress,the intensity of the high strain area of the series of regular dentate filling joint with the same filling degree series size gradually decreases,and the damage degree of the structural plane sample surface gradually increases,and the proportion of shear loss area gradually increases.(3)Based on the experimental process and theoretical analysis,the influence mechanism of filling degree on the shear of the series of regular dentate filling joint is discussed.Based on the Patton shear model,the empirical formula of peak shear strength of serrated filling structural plane under low normal stress is established.Comparing the measured values of this experiment with the calculated values of the empirical formula,the average error is 3.75 %,which basically meets the engineering needs.However,due to the limited data of this test,the influence of different weak interlayer materials,different rock joint materials,different rock joint sawtooth inclination angles and other factors are not considered.