ABSTRACT
The didactic experience shown that there are some properties and principles of soil mechanics whose understanding present certain difficulties for assimilation by the students. Due to this fact at the Geotechnical Department of Hydraulic Faculty was a constant concern to elaborate some physical models which allow a better understanding of soil and rock mechanics. The paper presents such models and illustrative tests. Thus for hydraulic behaviour there are models for illustration the influence of grain size on capillary rise, variation of water retention capacity with pore water suction (water characteristic curve), the influence of applied pressure on permeability of soils and unwoven geotextiles (the aedopermeameter), an apparatus to make conspicuous the filtration force. Parallel tests with two funnels filled with a sand and a silt give the opportunity to make conspicuous the difference between the permeability, water retention capacity and adsorptions of these soils. An other test with a test tube filled with a bentonitic suspension give the possibility to make conspicuous the tixotropy of this kind of soils. A balloon filled with sand connected to a vacuum pump allows to illustrate the principle of effective stress which is essential for understanding of soil behaviour. An other apparatus offers the opportunity to illustrate the liquefaction of a fine sand due to seepage force or to the dynamic stress. Concerning the soils with unstable structure there are different simple apparatus which make conspicuous the volume changes and swell pressure of active clays and the main factors (silica gel, sand particles, the bonding given by clay particles and calcite crystals) which contribute to the resistance of dry loess and to the collapse of structure during the wetting process.
