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In-situ mapping and documentation of rock faces using full-coverage 3D laser scanning techniques
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International Journal of Rock Mechanics & Mining Sciences 41 (2004) 379
SINOROCK2004 Paper 1A 23
In-situ mapping and documentation of rock faces using full-coverage 3D laser scanning techniques . Quanhong Feng*, K. Roshoff Berg Bygg Konsult (BBK) AB, Ankdammsgatan 20, Solna, SE-171 43, Sweden
Abstract A newly developed 3D laser scanning system is presented in this paper for 3D fracture mapping and documentation of rock faces. Comparing to traditional methods, the 3D laser scanner can quickly record a large amount of digital 3D information relating to an object. The scanner used in this study can rotate 360 in both horizontal and vertical directions, with a scanning radius up to 57 m. The area of the scanning field can also be adjusted by the computer program. Each scan takes a few minutes with a high-speed sampling rate of up to 625 000 points per second, with the optimal scanning resolution being about 3 mm. Each scanning point is recorded by four parameters, i.e. the 3D co-ordinates (X, Y, Z) and the reflex intensity. Therefore, the rock faces can be quickly recorded in three dimensions with a 3D digital model and image (3D gray-scale image), as shown in Fig. 1. By measuring a few reference points for each scan, the rock face can also be transformed into a geo-reference co-ordinate system, which enables the identification of any parts of a rock face in real space. Based upon the recorded co-ordinates of the scanning points, the geological information on the rock faces can be characterized. In the case study, some of the fracture parameters (i.e. dip angle, dip direction, spacing, trace length, roughness) were quantified by processing the laser scanning data with some specially developed programs. The case study shows that the orientation of the joint planes can be semi-automatically determined from 3D laser images; some of the joint parameters (e.g. spacing and persistence) can also be easily calculated from the 3D laser scanning data. In addition, large fracture surfaces can be quickly digitized directly from the rock faces, and then the roughness can be evaluated. In particular, the scale effect of fracture roughness can be investigated for a large fracture surface. The results obtained showed that the surface roughness of the scanned rock fracture is scale dependent at small scales and reaches stationarity at a size of about 3000 mm. It can be concluded that different sizes of fracture surfaces have different stationary limits, and therefore, for accurate characterization of rock fracture surface roughness, samples with a size larger than or equal to the stationary limit are required. More detailed results presented in this paper show a promising method for 3D mapping and documentation of rock faces for data acquisition in rock engineering. Keywords: 3D; Laser scanner; Rock face; Geological mapping; Documentation,Fracture parameters
Fig. 1. Scanning results of a rock fracture surface using the LARA system: (a) 3D co-ordinates of target points and (b) 3D model image.
*Corresponding author: Tel.: +46-8-759-5050; fax: +46-8-759-5065. E-mail address: [email protected] (Q. Feng). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.104
International Journal of Rock Mechanics & Mining Sciences 41 (2004) 379
SINOROCK2004 Paper 1A 23
In-situ mapping and documentation of rock faces using full-coverage 3D laser scanning techniques . Quanhong Feng*, K. Roshoff Berg Bygg Konsult (BBK) AB, Ankdammsgatan 20, Solna, SE-171 43, Sweden
Abstract A newly developed 3D laser scanning system is presented in this paper for 3D fracture mapping and documentation of rock faces. Comparing to traditional methods, the 3D laser scanner can quickly record a large amount of digital 3D information relating to an object. The scanner used in this study can rotate 360 in both horizontal and vertical directions, with a scanning radius up to 57 m. The area of the scanning field can also be adjusted by the computer program. Each scan takes a few minutes with a high-speed sampling rate of up to 625 000 points per second, with the optimal scanning resolution being about 3 mm. Each scanning point is recorded by four parameters, i.e. the 3D co-ordinates (X, Y, Z) and the reflex intensity. Therefore, the rock faces can be quickly recorded in three dimensions with a 3D digital model and image (3D gray-scale image), as shown in Fig. 1. By measuring a few reference points for each scan, the rock face can also be transformed into a geo-reference co-ordinate system, which enables the identification of any parts of a rock face in real space. Based upon the recorded co-ordinates of the scanning points, the geological information on the rock faces can be characterized. In the case study, some of the fracture parameters (i.e. dip angle, dip direction, spacing, trace length, roughness) were quantified by processing the laser scanning data with some specially developed programs. The case study shows that the orientation of the joint planes can be semi-automatically determined from 3D laser images; some of the joint parameters (e.g. spacing and persistence) can also be easily calculated from the 3D laser scanning data. In addition, large fracture surfaces can be quickly digitized directly from the rock faces, and then the roughness can be evaluated. In particular, the scale effect of fracture roughness can be investigated for a large fracture surface. The results obtained showed that the surface roughness of the scanned rock fracture is scale dependent at small scales and reaches stationarity at a size of about 3000 mm. It can be concluded that different sizes of fracture surfaces have different stationary limits, and therefore, for accurate characterization of rock fracture surface roughness, samples with a size larger than or equal to the stationary limit are required. More detailed results presented in this paper show a promising method for 3D mapping and documentation of rock faces for data acquisition in rock engineering. Keywords: 3D; Laser scanner; Rock face; Geological mapping; Documentation,Fracture parameters
Fig. 1. Scanning results of a rock fracture surface using the LARA system: (a) 3D co-ordinates of target points and (b) 3D model image.
*Corresponding author: Tel.: +46-8-759-5050; fax: +46-8-759-5065. E-mail address: [email protected] (Q. Feng). For full length paper see CD-ROM attached. doi:10.1016/j.ijrmms.2003.12.104