Complex problems in geotechnical engineering and soil mechanics can be investigated with physical modelling, where the structures in a geometrically n-times smaller scale are reproduced and the occuring forces and deformations are measured. Problematic is the reduction of pressures and the subsequent change of the mechanical behaviour of the model soil. The versatility of field and model test is shown by examples from the literature. In this thesis the similarity between barotropy and pyknotropy was used to model prototype soil behaviour. Soiltron is a prototype soil, which is treated with light and soft additives to achieve the same relative density in the model at an n-times smaller pressure as in the prototype. The stiffness and strength of the new material can be influenced to simulate prototype material behaviour by the control of the soil density. Thus, the use of that soil as material in small scale 1$g$models is possible. At the Institute of Geotechnical and Tunnel Engineering of the University of Innsbruck a model soil material was not available in sufficient quantity. Therefore, a large quantity of quartz sand was purchased and its mechanical behaviour was investigated in detail with triaxial test devices using local strain gauges. The specimen deformations were inspected with evaluation of remote measurements using PIV. Systematic and random test errors have been avoided or have been taken into account. Appropriate regressions have been found to relate pressure and density to the properties of the soil and to calculate the required density of Soiltron. The appropriateness of Soiltron is verified in two demonstration model tests. This work can be seen as foot step to strike a new path in physical modelling.