Characterization Of Roughness Of Rock Joints Based On Sampling Interval

The rock joints controls the mechanical properties such as deformation and failure of the rock mass,and the mechanical properties of the rock mass are closely related to the surface morphology.As a characteristic parameter describing the surface topography of the rock joints,JRC has been widely concerned by the scholars.A large number of studies have shown that sampling interval has a great influence on the characterization of surface roughness of rock joints.In this paper,we use MATLAB software to study the influence of sampling interval on JRC evaluation of roughness coefficient of rock joints from statistical parameter method and fractal dimension method of the two aspects.In this paper,the influence of sampling interval on the roughness coefficient of rock mass is revealed systematically.The main results obtained include:?1?The four empirical formulas of the roughness coefficient JRC and the statistical parameters Z₂ and the sampling interval?x are established,and the upper and lower bounds of the applicable range of sampling interval are given.The empirical formula takes into account the effect of sampling interval on roughness coefficient estimation.By using this method,the JRC value corresponding to the standard profiles at different sampling intervals can be obtained quickly and simply,and the new JRC formula can be applied more widely.?2?A fractal evaluation method for roughness of rock joints under optimal sampling interval is proposed.The method take into account influence of the true length of the profile and the number of measurement times,and analyzes the relationship between the fractal dimension D and the sampling interval.The optimal sampling interval is proposed and the relationship between JRC and the fractal dimension D of the rock mass is established based on the optimal sampling interval,and the JRC value can be estimated more accurately.?3?Study on evaluation of roughness coefficient of rock mass.The effect of size effect,anisotropy and sampling interval on the evaluation of of rock joints was studied by using the calcareous slate structure in Changshan County,Zhejiang Province.The single variable principle was used in the analysis,and the remaining two factors remain unchanged.The JRC values of different sizes are calculated by analyzing the profiles of the rock joints of ten sizes?10,20,.....,100 cm?.At the interval of 15°,a total of 24 sampling directions were selected to calculate the JRC value of the rock joints in all directions.Taking 0.1 cm as the interval,the JRC value corresponding to the ten sampling interval of 0.1-1 cm are calculated.The variation law of JRC with sampling size,sampling direction and sampling interval is analyzed respectively.