PRACTICAL VISUALIZATION OF ROCK STRUCTURE

The conventionally applied method for visualizing the structure of a r ock mass is limited to plotting the orientation of individual disconti nuities by using the Schmidt stereographic net. Their spacing is not i llustrated and other structural features, such as undulation and twist ing, cannot be interpreted from such stereographic views. A new mode o f visual presentation of rock structural features of one or several di fferent types in rock volumes of any size that makes all this possible is proposed in the present report. The primary purpose is to quantify , for all elements of a rock mass where the structure has been evaluat ed by borehole investigations or mapping in the course of underground excavation, the orientation and average spacing of defined discontinui ties like hydraulically and mechanically active fractures. These local structural patterns, which are plotted on three of the six faces of c ubical boxes with defined edge length and with one edge oriented N-S c an be combined by applying the mathematical tool for connecting faces with which certain visualization codes like Alias Sketch are equipped. This combines different local rock structures to form regional patter ns that can reveal undulation and twisting and important variations in spacing of major discrete discontinuities. Visualization can be given in true perspective or orthographic form and larger discontinuities t hat have been identified in the field, such as fracture zones. can be introduced in the model for correlation with smaller Features. Further more, the stress situation at all sites where rock stress measurements have been made can be visualized in the model in the form of principa l planes. The proposed models can be visualized from any ''camera angl e'' and also shown in Quick Time VR form. i.e. as being slowly rotated around any predetermined axis. This facilitates definition and select ion of the rock structure, local or regional, for numerical calculatio ns. (C) 1998 Elsevier Science B.V. All rights reserved.