The subgrade is one of the most important elements of both the railway and the road. The serviceability of the railway track and the strength of the road clothing of the highway depend on the stability of the subgrade.
The soils located on the highway serve as the basis on which the embankments are built and the material for the construction of embankments. In the same soils, recesses are arranged. The stability of embankments and recesses largely depends on the properties of the soils. Therefore, work on the construction of earthen structures must be preceded by the study of the properties of soils located along the highway.
In conditions of natural occurrence, soils consist of: 1) solid particles, or soil itself, 2) associated with the soil of water and 3) air filling the pores of soil from water.
The quantitative ratio of these components and the quality of solid particles determine the physical properties of soils. To determine these properties, the production of laboratory testing of soils is necessary, the most important of which are definitions: grain (granulometric) composition, plasticity, natural and optimal humidity and volumetric weight.
The determination of the grain composition of the soil is made in the laboratory. In conditions of construction, simplified methods of determining the content of sand, dusty and clay particles in the soil by lingering and processing with chloride calcium are often used.
According to the content of sandy, dusty and clay particles of soils can be conditionally divided into varieties.
