International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Cenospheres are used in a variety of applications, including as fillers in building, construction, plastic, and composite materials. The aim of this paper is to evaluate the effect of particle size on the mechanical-acoustic properties of cenosphere powders, which were produced in two different sizes. The mechanical-acoustic properties of the studied powders were experimentally determined based on the frequency dependencies of the sound absorption coefficient, using the transfer function method. It can be concluded that not only particle size, but also powder bed height and the excitation frequency of acoustic waves, significantly influenced the mechanical-acoustic properties of the studied cenospheres.

The physical and mechanical properties of soil change dynamically following each tillage and rainfall. Some of the more important ones are bulk density, (g cm⁻³), hydraulic conductivity in soils, saturated with water, (cm day⁻¹), the rainfall curve, the temperature (^оС) and the capacities of soil to retain water at saturation point (cm³ cm⁻³). Theoretically, only the upper 30 cm of soil layer experience change in the physical and mechanical properties, caused by tillage. The actual depth of the changes in the soil depends on the production technology selected. Various types of tillage are applied worldwide, corresponding to the level of development of socio-economic formations and of the production technologies. In Bulgaria, the traditional annual ploughing of soil is applied, including on slopes, giving a prerequisite for the subsequent negative consequences, such as activation of erosion processes and degradation.