IN-SITU MAPPING AND DOCUMENTATION OF ROCK FACES USING A FULL-COVERAGE 3D LASER SCANNING TECHNIQUE

摘要

A newly-developed 3D laser scanning system was presented in this paper for 3D fracture mapping and documentation at rock faces. The presented 3D laser scanner can quickly record a great amount of digital 3D information of an object. Each scan takes about 1-6 minutes (depending upon the resolution) at a high-speed sampling rate up to 625 000 points per second with the optimal scanning resolution about 3 mm. The scanner can rotate 360 degrees in both horizontal and vertical directions with a scanning radius up to 57 meters. Every scanning point was recorded by 4 parameters, i.e. 3D co-ordinates (X, Y, Z) and the reflex intensity. Therefore, the rock faces can be recorded as 3D digital model and image. In the case study, fracture parameters, e.g. orientation, spacing, persistence, roughness, were quantified by some specially developed programs. It shows that orientation of joint planes can be semi-automatically determined from 3D laser images, joint spacing and persistence can also be calculated from 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. Especially, the scale effect of roughness was investigated for a large fracture surface, and indicated that the fracture surface roughness is scale-dependent at small scales and becomes stable after reaching to a stationary size.