Pull experiment to validate photogrammetrically predicted friction angle of rock discontinuities

Abstract The estimation of the mechanical properties of rock joints is crucial in terms of safety when it comes to design of slopes in open pit mines or caverns used for the storage of hazardous materials, for instance – nuclear waste. Photogrammetry provides a simple, objective method for joints roughness assessment, without the need for expensive and time consuming laboratory tests or subjective empirical methods. In this study, a new photogrammetric method was used to estimate the roughness, shear strength and friction angle of a discontinuity of 2 m by 1 m fresh rock joint. The estimation was done by analyzing the profiles of digital models of joint surface. Surface Length and Slope Measurement methods were used to calculate the values of Joint Roughness Coefficient (JRC) of analyzed surfaces. Next, the shear strength and friction angle of the rock discontinuity were obtained experimentally with multistage pull testing. The results obtained with both methods were analyzed and compared. JRC values from photogrammetrically created digital models of the joint surface were overestimated due to the low density of the models, which resulted in high noise to signal ratio. Shear strength obtained with photogrammetrically created models were overestimates in relation to the results of the pull test by approximately 45%. The errors made during this research are analyzed in the article and recommendations on how to improve reliability of the results are made. Main error in photogrammetric prediction was low density of the point clouds and in laboratory test too low stiffness of the test arrangement. The alternative methodology for photogrammetric studies used in previous stage of the research project was tested during this study and was proven to give significantly higher accuracy of generated digital models. The stiffness of the testing machine and proper positioning of the sample halves on top of each other were identified as the most sensitive aspects of methodology of big scale pull test when it comes to the reliability of results.

[1]  Giovanni Grasselli,et al.  ISRM Suggested Method for Laboratory Determination of the Shear Strength of Rock Joints: Revised Version , 2013, Rock Mechanics and Rock Engineering.

[2]  I. Norman,et al.  ROCK SLOPE STABILITY ANALYSIS , 2018 .

[3]  A. Karakas.  Practical Rock Engineering , 2008 .

[4]  Håkan Stille,et al.  A conceptual model for the peak shear strength of fresh and unweathered rock joints , 2014 .

[5]  Giovanni Grasselli,et al.  Shear strength of rock joints based on quantified surface description , 2001 .

[6]  A. Malinverno.  A simple method to estimate the fractal dimension of a self‐affine series , 1990 .

[7]  J. Zhao,et al.  Joint surface matching and shear strength part A: joint matching coefficient (JMC) , 1997 .

[8]  Changchang Wu,et al.  SiftGPU : A GPU Implementation of Scale Invariant Feature Transform (SIFT) , 2007 .

[9]  H. R. Pratt,et al.  The effect of speciment size on the mechanical properties of unjointed diorite , 1972 .

[10]  L. Uotinen,et al.  Photogrammetric calculation of JRC for rock slope support design , 2016 .

[11]  Pinnaduwa Kulatilake,et al.  New peak shear strength criteria for anisotropic rock joints , 1995 .

[12]  N. Barton,et al.  The shear strength of rock joints in theory and practice , 1977 .

[13]  Dong Hyun Kim,et al.  The determination of joint roughness coefficient using three-dimensional models for slope stability analysis , 2013 .

[14]  Allen W. Hatheway,et al.  The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring; 1974–2006 , 2009 .

[15]  Lu Zhang,et al.  A new method estimating the 2D Joint Roughness Coefficient for discontinuity surfaces in rock masses , 2014 .

[16]  Quantifying loss of geometrical features in downscaling of rock joint surfaces using shear box replica series , 2016 .

[17]  Steven M. Seitz,et al.  Multicore bundle adjustment , 2011, CVPR 2011.

[18]  C. Edelbro,et al.  Small Scale Joint Surface Roughness Evaluation Using Digital Photogrammetry , 2012 .

[19]  Nick Barton,et al.  Review of a new shear-strength criterion for rock joints , 1973 .

[20]  Giovanni Grasselli,et al.  A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials. , 2009, The Review of scientific instruments.

[21]  S. Ullman.  The interpretation of structure from motion , 1979, Proceedings of the Royal Society of London. Series B. Biological Sciences.

[22]  H. Melin.  Controlling parameters for normal and shear behaviour of rock fractures-a study of direct shear test data from SKB , 2012 .

[23]  F. Johansson.  Shear Strength of Unfilled and Rough Rock Joints in Sliding Stability Analyses of Concrete Dams , 2009 .

[24]  Terry E. Tullis,et al.  Euclidean and fractal models for the description of rock surface roughness , 1991 .

[25]  Pierre Londe.  The role of rock mechanics in the reconnaissance of rock foundations , 1973, Quarterly Journal of Engineering Geology.

[26]  M. Ahola,et al.  Assessment of conventional methodologies for joint roughness coefficient determination , 1993 .

[27]  Nick Barton,et al.  Shear strength criteria for rock, rock joints, rockfill and rock masses: Problems and some solutions , 2013 .

[28]  N. Kolecka.  PHOTO-BASED 3D SCANNING VS. LASER SCANNING – COMPETITIVE DATA ACQUISITION METHODS FOR DIGITAL TERRAIN MODELLING OF STEEP MOUNTAIN SLOPES , 2012 .

[29]  Stephen R. Brown.  A note on the description of surface roughness using fractal dimension , 1987 .

[30]  Joni Sirkiä.  Requirements for initial data in photogrammetric recording of rock joint surfaces , 2015 .

[31]  David G. Lowe,et al.  Object recognition from local scale-invariant features , 1999, Proceedings of the Seventh IEEE International Conference on Computer Vision.

[32]  Richard Szeliski,et al.  Towards Internet-scale multi-view stereo , 2010, 2010 IEEE Computer Society Conference on Computer Vision and Pattern Recognition.

[33]  J. Carr,et al.  The fractal dimension as a measure of the roughness of rock discontinuity profiles , 1990 .

[34]  D. Cruden,et al.  ESTIMATING JOINT ROUGHNESS COEFFICIENTS , 1979 .

[35]  Norbert H. Maerz,et al.  Joint roughness measurement using shadow profilometry , 1990 .

[36]  Lauri Uotinen,et al.  Determination of joint mechanical parameters for stability analysis in low stress open pit mines , 2016 .