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Keywords: digital image correlation, rock joint, joint roughness coefficient.

Summary

The joint roughness coefficient (JRC) is used to estimate the influence of rock joint roughness on shear strength. The traditional methods to evaluate the JRC are stylus and laser profilometers. They can scan the profile of the rock joint point by point. Then the three-dimensional coordinates obtained can be used to evaluate the JRC value. The disadvantage of these traditional methods is that they cost much time or the cost of the instrument is too high. They are not suitable for in-situ testing. Therefore a simple three dimensional digital image correlation (DIC) method is developed in this research to evaluate the JRC.

All of the traditional three dimensional DIC methods use two cameras to capture the images. The first process of these methods is to calibrate the positions of the cameras. There are many different methods to calibrate the positions of the image acquisition instruments. The precision of the calibration will influence the measurement results. In this research, a simplified three-dimensional DIC method is proposed. In this method, only one camera is used. The specimen is put on an X-Y-Z table. The movement of this table can be precisely controlled. The position of the camera must be calibrated at first. A calibration parameter is determined in the experimental process. Then this parameter will be applied to calculate the z coordinates of the joint surface.

The specimen will be moved for a certain displacement horizontally. The images of the specimen before and after movement will be captured. These two images are captured by the same image acquisition instrument. That is to say, the optical characteristic by capturing two images will not be changed. This can reduce the errors of the measurement. Then these two images will be analyzed. The profile of the rock joint and the JRC can be evaluated. The advantages of this method are that the cost of the necessary instrument is relatively low, it has no complicated calibration processes and it is suitable for the in-situ test.

The following conclusions can be drawn according to the analysis results:

The DIC method is a non-contact measurement technique. It will not disturb the specimen. Therefore it can avoid damaging the specimen. Then the measurement error due to specimen damage can also be ignored.
The analysis results show that the JRC value measured by three-dimensional DIC method very close to the JRC value measured using a three-dimensional laser scanner. It shows the correctness of three-dimensional DIC method.
The three-dimensional DIC method can be used to measure the JRC value of different scales. It can also be applied to measure the in-situ joint roughness. Therefore the three-dimensional DIC method has more utility value than the three-dimensional laser scanner.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 91 PROCEEDINGS OF THE TWELFTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING Edited by: B.H.V. Topping, L.F. Costa Neves and R.C. Barros Paper 229 Evaluation of the Joint Roughness Coefficient using the Digital Image Correlation Method S.H. Tung¹, M.H. Shih² and J.C. Kuo³ ¹Department of Civil and Environmental Engineering, National University of Kaohsiung, Taiwan ²Department of Construction Engineering, National Kaohsiung First University of Science and Technology, Taiwan ³Department of Materials Science and Engineering, National Cheng-Kung University, Tainan, Taiwan doi:10.4203/ccp.91.229 purchase the full-text of this paper Full Bibliographic Reference for this paper S.H. Tung, M.H. Shih, J.C. Kuo, "Evaluation of the Joint Roughness Coefficient using the Digital Image Correlation Method", in B.H.V. Topping, L.F. Costa Neves, R.C. Barros, (Editors), "Proceedings of the Twelfth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 229, 2009. doi:10.4203/ccp.91.229 Keywords: digital image correlation, rock joint, joint roughness coefficient. Summary The joint roughness coefficient (JRC) is used to estimate the influence of rock joint roughness on shear strength. The traditional methods to evaluate the JRC are stylus and laser profilometers. They can scan the profile of the rock joint point by point. Then the three-dimensional coordinates obtained can be used to evaluate the JRC value. The disadvantage of these traditional methods is that they cost much time or the cost of the instrument is too high. They are not suitable for in-situ testing. Therefore a simple three dimensional digital image correlation (DIC) method is developed in this research to evaluate the JRC. All of the traditional three dimensional DIC methods use two cameras to capture the images. The first process of these methods is to calibrate the positions of the cameras. There are many different methods to calibrate the positions of the image acquisition instruments. The precision of the calibration will influence the measurement results. In this research, a simplified three-dimensional DIC method is proposed. In this method, only one camera is used. The specimen is put on an X-Y-Z table. The movement of this table can be precisely controlled. The position of the camera must be calibrated at first. A calibration parameter is determined in the experimental process. Then this parameter will be applied to calculate the z coordinates of the joint surface. The specimen will be moved for a certain displacement horizontally. The images of the specimen before and after movement will be captured. These two images are captured by the same image acquisition instrument. That is to say, the optical characteristic by capturing two images will not be changed. This can reduce the errors of the measurement. Then these two images will be analyzed. The profile of the rock joint and the JRC can be evaluated. The advantages of this method are that the cost of the necessary instrument is relatively low, it has no complicated calibration processes and it is suitable for the in-situ test. The following conclusions can be drawn according to the analysis results: The DIC method is a non-contact measurement technique. It will not disturb the specimen. Therefore it can avoid damaging the specimen. Then the measurement error due to specimen damage can also be ignored. The analysis results show that the JRC value measured by three-dimensional DIC method very close to the JRC value measured using a three-dimensional laser scanner. It shows the correctness of three-dimensional DIC method. The three-dimensional DIC method can be used to measure the JRC value of different scales. It can also be applied to measure the in-situ joint roughness. Therefore the three-dimensional DIC method has more utility value than the three-dimensional laser scanner. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £140 +P&P)
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