ABSTRACT:

In rock engineering, geological mapping at exposed rock faces is one of several important approaches to investigate how geological factors affect mechanic and hydraulic properties of the rock mass. A typical mapping procedure at exposed rock faces consists of two steps: i) capturing the required data in the field; ii) documenting the mapping information from the field data, A new approach presented in this paper aims to apply new techniques for automatic collection of the field data and documentation of the geological information. In this study, the field data were collected by combined use of non-reflector geodetic total station, close-range digital photogrammetry and 3-D laser scanner. Then, mapping information were documented in an integrated way by attributive tables thematical diagrams, images, 2-D and 3-D computer graphics, 3-D geometrical and textural models. Since the mapping information are captured in a spatial reference system, it is possible to record both quantitative and spatial analysis of geological properties of rock masses. Methodology and results of a case study are presented in this paper.

I.
INTRODUCTION

Exposed rock faces, either above or below the ground, are used to investigate geological features of rock masses. To quantify the influence of geological factors on mechanic and hydraulic properties of rock masses, it is important to use an efficient method for guaranteeing quality and quantity of the mapping information required in modern rock engineering. Because of the drawbacks inherent in traditional mapping Methods, several research groups have been working for developing new techniques, e.g. image processing (Reid and Harrison, 1996, 2000; Kanduth and Corthesy, 1999), photogrammetry (Coe, 1995; Harrison, 1993; Beer et al., 1999) and geodetic total station (Bulut et al., 1996, Feng, 1999),for collecting and documenting geological information exposed at rock faces. The study presented in this paper aims to introduce a new approach for quantifying and presenting the geological information collected from exposed rock faces. A typical mapping procedure consists of two steps: I) capturing the required data from the exposed rock faces; 2) documenting and processing the logged information from the recorded data in order to generate the required information. In this study, three new techniques, i.e. non-reflector geodetic total station, close-range digital photogrammetry and 3-D laser scanner, were applied for field mapping on exposed rock faces. The data can be automatically captured in a three-dimensional local reference co-ordinate system, and linked to a global co-ordinate system, without physically touching on the rock faces. So, both quantitative and spatial analysis of mapping information become possible. The mapping data are captured as both quantitative data and visual images, geological information can then be more efficiently extracted from the raw data. The presented methods also enable us to document the geological information in multiple approaches (e.g. attributive tables, 2-D and 3-D graphics and images), which might be useful for further analysis and rock engineering design.

2.
COLLECTION OF THE MAPPING DATA FROM EXPOSED ROCK FACES

In this study, three methods have been used for capturing the mapping data from exposed rock faces.

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