The paper is intended to pay homage to Professor Leopold Müller who was a leading developer and user of physical models. This will be done by reviewing physical models of fundamental material behavior, geologic mechanisms, and especially jointed rock. On this basis complex models of geologic processes and of structures on and in rock masses will be discussed. As will be shown this sequence of topics also corresponds to the history of physical models. Finally, critical aspects, namely the issues of scaling and of obsoleteness because of powerful simulation models will be addressed leading to the outlook as to where physical models can and should be used.
The paper is intended to pay homage to Professor Leopold Müller who was a leading developer and user of physical models to solve fundamental rock mechanics problems and complex engineering cases. Professor Müller not only used Physical Models extensively but also wrote a seminal paper (Müller,1980), in which he discussed other types of models and addressed the skepticism with which physical models were looked at. Today we face a similar situation in that the use of physical models is questioned in comparison to the possibilities of powerful computer-based simulations.
I intend to address this issue by looking at models of materials, of geologic processes, and of jointed rock masses to end up with complex models such as slope instabilities and tunnels in rock masses. This sequence of model topics also fits well into the history of physical models. Finally, to bring physical modeling into the context of present-day engineering and science the paper will compare the principles and use of physical models with those of simulation models.
To start this section the discussion (dialogo secondo) by Galileo Galilei (1638) on bending (Fig. 1) is used. Figure 1 is not the picture of a physical model but of a conceptual one. It is used because it shows two aspects (among others) of Galilei's interpretations: The correct one is related to scaling: multiplying (e.g., doubling) the dimensions does not increase the loading capacity by the same factor. The incorrect one is the assumption that the tensile stresses are uniform at section A-B. If a physical model test had been run this mistake would have been discovered. This is a pertinent lead-in to the paper – PHYSICAL MODELS AND SCALING OF PHYSICAL PROCESSES are essential.