Quantitatively Estimating The Joint Roughness Coefficient Value Of Rock Structural Plane Based On Three-Dimensional Scanning

In rock mass engineering,the distribution characteristics of the structural plane and its shear strength are the most important factors controlling the stability of rock mass.Among them,the shear strength of the structural plane usually needs to be obtained through laboratory tests or in-situ tests,but these works also have its insufficiency,such as in-situ test will be subject to site conditions.The Barton shear strength formula is a widely used calculation method,but the joint roughness coefficient(JRC)is difficult to determine accurately.The purpose of this thesis is to quantitatively estimate the JRC of the rigid structural plane.Based on the three-dimensional scanning,direct shear test and rebound test of the structural plane,the three-dimensional topographical features of the rock mass are analyzed,and the method of quantitatively estimating the JRC is obtained.The research contents in this thesis are as follows:(1)The three-dimensional morphological features of the structural plane are obtained by three-dimensional scanning,and ten profiles are uniformly taken along the shearing direction on the scanned structural plane,and the curve features(point coordinates)of the respective profiles in the shear direction are obtained,and further obtain the climbing angle i_i,the climbing height h_i,the area S of each profiles,and then obtain the average value of the 10 profiles climbing angle and the climbing height;(2)The JRC of each profile of structural plane which had been back-calculated based on the shear test results and the Barton shear strength formula.then,the back-calculated JRC is taken as the true value;(3)By using the curve characteristics of each profile in the shear direction and the back-calculated JRC which had been taken as true value,the formula of the relationship between the structural surface topography and the JRC quantitative estimation considering the shear direction is obtained through comparative analysis.The results show that when the combination of area ratio,climbing height and climbing angle are used,the JRC maximum error calculated by the fitting equation is 1.7 which is very small.Therefore,these parameters can be used to quantitatively estimate the JRC.