ABSTRACT

Geotechnical analyses in rock engineering practice often rely on simple models. More advanced analysis methods suffer from the lack of information of geotechnical data. Input parameters have to be estimated. If a reasonable estimation is not possible, advanced analysis methods should not be applied. One possibility to improve the geotechnical data acquisition is the application of a remote sensing system and the generation of metric 3D images. Metric 3D images serve as the basis for the assessment of geometrical rock mass properties as well as the size and shape of the outcrop. Evaluations from 3D images facilitate the establishment of a 3D discontinuity network, the determination of discontinuity properties (such as orientation, spacing, trace lengths, etc.) and the geological interpretation. A short review on the development and currently available remote sensing methods is given. The principle of30 imaging is discussed considering as example the JointMetriX30 system which has been applied in this study. The contribution of data obtained from 3D images to slope analysis methods is described on an advanced block analysis method and the estimation of rock mass properties for numerical analysis.

INTRODUCTION

The design of engineering structures related to the excavation and/or support of ground should base on a geological and geotechnical ground model. The final excavation and support is selected according to the response of the ground model to applied excavation geometries and sequences and support measures. Different fields of application will call for different requirements. Permanent civil engineering structures require a more detailed analysis with a higher safety level compared with temporarily existing structures in mining. Nevertheless, the comparison of the response of the ground with the established requirements is common in the design procedures of all fields of application.

The acquisition and evaluation of geological and geotechnical data are integrated parts during the investigation and design stage. This process results in a ground model which contains all relevant information for the design of engineering structures. It serves as input for decision making processes during different phases of projects, ranging from feasibility studies to construction and maintenance.

Traditional methods of geological data acquisition Are prone to errors. There are sampling difficulties, human bias, and instrument errors. Time and access restrictions lead to incomplete data sets. As a consequence, the resulting data usually do not allow objectively reproducing the actual rock mass conditions. Especially in mining and underground construction information which has not been recorded, gets lost as the excavation process proceeds.

The presented JointMetriX3D system overcomes those problems and opens new possibilities for optimisations concerning design, safety, and productivity. The core of the JointMetriX30 system is the generation of a high-resolution metric 3D image of a rock surface which is analysed and assessed on a computer. The 3D image is an objective documentation of the rock mass conditions which allows for instantly available geometric measurements at an arbitrary number without access restrictions.

Consistent analysis methods in rock engineering should follow a hierarchical procedure and comply with defined requirements.

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