This paper proposes a new technique to evaluate the stability of a tunnel as an application of fractal geometry in the field of tunnel construction, and introduces a case in which this technique was actually applied to tunnel construction. This technique consists of two methods. One method is predicting the position of faults ahead of a tunnel face, and the other is evaluating the tunnel support pattern.
Ce document propose la nouvelle technique qui evalue la' stabilite des tunnels comme application de la geometrie fractale dans le domaine de la construction des tunnels, et introduit le cas pour lequel cette technique a ete appliquee effectivement à la construction de tunnels. Cette technique consiste en deux methodes. Une methode predit la position des defauts devant la face du tunnel, tandis que I'autre methode evalue la configuration du support de tunnel.
In dieser vorliegenden Abhandlung wird eine neue Technik vorgeschlagen, die Beurteilung der Stabilitat von Tunneln durch die Anwendung von Fraktal geometrie im Tunnelbau ermöglicht; darueber hinaus wird ein konkretes Anwendungsbeispiel dieser Technik beschrieben, Die Technik besteht die den beiden folgenden Verfahren: Prognose der Position von Verwerfungen vor der Tunnelstirnseite und Beurteilung der ~orm der Tunnelabstuetzung.
The stability of constructing tunnels at jointed rocks is susceptible to geological characteristics depending on the extent of cracking and weathering. Thus, predicting the geological characteristics of these rocks ahead of a tunnel face is very important both from a safety hazard point of view and economical construction of the tunnel. Moreover, a system for objectively and rapidly evaluating the geological conditions is necessary to choose the correct tunnel support pattern.
This technique can be used in the daily construction management without the need to suspend construction. Moreover, it has the advantage that analysis can be done in real time using a digital camera and e-mail.
The pictures of the tunnel face were taken on site using a digital camera and fractal analysis was done. The picture of the tunnel face was made to represent the fractal dimensions by image processing and fractal analysis was conducted using the box-counting method. Prediction of the fault position ahead of the tunnel face is based on changes in these fractal dimensions, and evaluation of the tunnel support pattern is based on the value of each fractal dimension.
In actual tunnel construction application, the results conformed well with the prediction of the fault position ahead of the tunnel face, and good correlation was recognized between the fractal dimensions and the tunnel support pattern.
The geometrical characteristics such as the density of rock mass fractures in the tunnel face were evaluated quantitatively by fractal dimensions. This quantifying of rock mass fractures by fractal dimensions consists of both image processing of pictures of the tunnel face and fractal dimension analysis of post-image processing.
First, image processing of the tunnel face picture was done using a picture taken on site using a digital camera.
