Method for Measuring and Detecting Fracture Plane Orientations in the Condroz Sandstone with 3D Terrestrial LIDAR Data

Broeksma, R.E.

Method for Measuring and Detecting Fracture Plane Orientations in the Condroz Sandstone with 3D Terrestrial LIDAR Data

Title

Method for Measuring and Detecting Fracture Plane Orientations in the Condroz Sandstone with 3D Terrestrial LIDAR Data

Author

Broeksma, R.E.

Contributor

Lindenbergh, R.C. (mentor)
Abels, H.A. (mentor)

Faculty

Civil Engineering and Geosciences

Department

Geoscience & Engineering

Date

2016-11-07

Abstract

Several methods are used to measure fracture plane orientation. For these measurements manual, photogrammetric and laser scanning methods are in use. The latter method is used in this thesis to survey the geometry of an outcrop of the Devonian Condroz Sandstone Group in southern Belgium.The aim of this thesis is to develop a method with which the orientation of fracture planes in the Condroz Sandstone outcrop can be measured using LIDAR data. To this end, the research question is as follows: How can LIDAR data be used to find the orientation of fracture planes in the Condroz outcrop? LIDAR (i.e. Light Detection and Ranging) is a laser scanning method that captures the geometry of an object by illuminating the surface with a laser light. The fracture planes width varies between a couple of centimeters up to several meters.The research question is answered through developing a method for detecting and measuring fracture planes. The geometry of a rock face is captured in a point cloud. The normal vectors to all points in this cloud are determined and the azimuth of each point is put in a histogram. By selecting the second largest peak in this histogram and applying a nearest neighbour elimination, all points that belong to the fracture plane are selected. The dip direction and angle, which make up the orientation, are determined by selecting the median of this data set. Applying this method on several fracture planes, surveyed in the researched outcrop, seem to endorse the applicability of this method. The found results range in between the expected results after visual observations and comparison with another study. However, the validation of the results is poor, because exact measurements of the orientation of the studied fracture planes is missing. The developed method gives a basis for further research to validate, improve and automate the proposed method. This method can be used in other researches about orientation analysis using LIDAR data.

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