Research On The Undulation Characteristics Of Rock Joint Based On Anisotropic Variation Coefficient

The anisotropy in the rock joint is the main influencing factor that leads to the uncertainty of the rock mass mechanical behavior.The anisotropy is due to the undulating morphology of the joint surface.Therefore,the study of anisotropic characteristics based on the undulating morphology has great theoretical significance for grasping the mechanism of joint anisotropy.At present,the joint anisotropy is basically represented by plotting the roughness parameters obtained in different directions on the polar plots,and the degree of anisotropy is determined by the ratio of the minimum roughness to the maximum roughness.This method can reflect the anisotropic variation of the structural plane to a certain extent,but there are also some shortcomings,that is,the statistical distribution of the joint anisotropy around the roughness parameters is impossible to establish internal relationship between the surface morphology and anisotropy.In addition,it is more difficult to characterize the scale variation of the degree of overall anisotropy,resulting the study of joint anisotropy remains at the stage of description of properties.In view of those concerns,we summarize the distribution law of anisotropy by investigating the anisotropic distribution maps of rock joint in the existing researches,and propose an anisotropic characterization model of rock joint based on the contribution rate of undulations.The relationship between the surface morphology and anisotropy under the different contribution rates.On this basis,the coefficient AVC?Anisotropic Variation Coefficient?for quantitatively describing the degree of structural surface anisotropy change is defined,and the theoretical anisotropic distribution function for analyzing the anisotropic variation behavior of the joint is derived.Finally,the proposed AVC is used to study the size effect law of joint anisotropy.According to the research approach mentioned above,research on characterization of rock joint surface anisotropy considering the contribution rates of undulations is carried out.The results are obtained as follows:?1?Based on the investigation of anisotropic distribution characteristics,it is found that there is a specific distribution law of joint anisotropy.This law considers that the surface morphology of the actual joint plane is composed of superposition of regular joint plane in orthogonal directions,and the anisotropic variation determined by the contribution rates.Based on the above-mentioned distribution law,the three-dimensional regular joint surface morphology function is established,and the anisotropic joint characterization model is constructed by combining MATLAB.The AVC is defined by characterizing the variable relationship between the contribution rates in orthogonal direction to reflect the anisotropic variation behavior.According to the proposed characterization model,seven different joint surfaces with AVCs equal to0,0.2,0.4,0.6,0.8,0.9 and 1.0 were constructed,and their anisotropy was measured by two-dimensional roughness parameters.It is found that AVC effectively reflects the change of joint from anisotropy to isotropic,and the smaller the AVC,the more prominent the anisotropic behavior.Therefore,the level of anisotropic variation in six different intervals is divided to effectively quantify the degree of anisotropy variation.?2?According to the assumption of anisotropic arc distribution,the influence of the variation of the roughness parameters on the anisotropy distribution in the orthogonal direction is analyzed,and the theoretical distribution function of the anisotropic variation behavior is derived.By predicting the anisotropic distribution of four composite joint surfaces based on Barton standard profiles,it is found that the actual values of the roughness parameters corresponding to different AVC values are almost consistent with the theoretical derivation values in all directions,and the average relative error is stable within 10%.It is shown that the derived function can better analyse the anisotropic variation behavior of the joint.In order to better apply to the natural joint,an adaptive algorithm that can automatically match the orthogonal directional parameters to anisotropic analysis is written.By evaluating the anisotropic behavior of two natural rock specimens,the results show that the proposed anisotropic analytical algorithm can effectively estimate the theoretical distribution characteristics of natural joint anisotropy.?3?In order to consider the three-dimensional effect of anisotropy,the anisotropic variation coefficient AVC^3D,which consider the three-dimensional shape parameters of orthogonal directions,is proposed.The AVC^3D of ten scales samples of four kinds of Slate rock joints are measured based on the full coverage of the overlapping sampling method,and the size effect law of the AVC^3D is obtained.The conclusions are as follows:the AVC^3D shows a variation law that with the increase of the size of rock joints,the AVC^3D reduce to stable.The model of attenuation can be AVC^3D and the normalized size of the rock joints show a good linear function,indicating that the size effect of AVC^3D has a fractal structure.The fractal dimension D of the AVC^3D,which does not vary with the scales,can achieve the regular statistics of the size effect of the AVC^3D.This method reveals the mechanism of the effective contact area growth rate which affects the directional change of surface topography gradually less than the sampling size.It shows that when the rock joint reaches the threshold of the anisotropic size effect,the stable anisotropy will appear.