Increasingly complex design systems require an individual approach when determining the necessary design parameters. As soils are characterized by strong strain-dependent nonlinearity, test methods used to characterize the subsoil should be carefully selected, in terms of their "sensitivity" as well as suitability for the analyzed type of problem. When direct measurements are not available, while design calculation models require specific parameters, indirect parameter estimation may be used. This approach requires calibration and validation of empirical correlations, based on well documented database of tests and case studies. One of the parameters often used, when analyzing soil-structure interaction problems, is the shear stiffness of the soil and its strain-dependent degradation. The aim of the article is to present the procedure for description and evaluation of soil stiffness based on field tests (CPTU, DMT and SDMT) and a large number of reference curves obtained from laboratory tests (TRX) for selected soil types. On the basis of the given algorithm, it is possible to obtain a stiffness module G0 value at any level of deformation, based on in-situ tests.

The objective of this paper is to identify non-metallic inclusions occurring in aluminium-killed steel with regulated sulphur content and modified with calcium, explain the reaction between calcium and non-metallic inclusions and identify secondary metallurgy parameters, which condition obtaining such forms of inclusions to be favourable to improvement in steel machinability. Computer-aided thermodynamic calculations and production experiments were carried out. They enabled to determine technological parameters of treatment in liquid steel ladle deoxidised with silicon and aluminium, with low (0.01%) and increased (up to 0.03%) sulphur content. By comparison of the computer-aided simulations and production experiment results it was found that calcium in the steel both modifies the aluminium oxide inclusions and reacts with sulphur, whereas deep desulphurisation (below O.Ol%) is favourable to oxide modification. Non-metallic inclusions of calcium aluminates, which affect positively the rnachinability of steel, appear in liquid state in the steel bath. During conventional casting and cooling down large ingots of steel with increased sulphur content, aluminates are significantly depleted in calcium as a result of reaction between calcium and sulphur dissolved in these aluminates and steel matrix. To obtain aluminates and (Ca,Mn)S sulphides rich in calcium in finished products accelerated steel cooling is to be applied, which takes place during continuous steel casting. In steels modified with calcium, there is higher homogeneity of distribution and sizes of inclusions on finished products' cross-section and higher globularisation of these inclusions in comparison to non-modified steels. Improved steel machining properties in these steels and improved isotropy of mechanical properties in bars made from it were found.