This paper presents an extensive comparative analysis of the experimental results of chemical stabilisation of clayey soil in laboratory conditions by comparing the effects of adding conventional stabilisers (lime, cement binder), stabilisers that can be considered as waste material (fly ash, rock flour), as well as alternative chloride-based materials (ferric chloride, calcium chloride, potassium chloride) on the geomechanical properties of the soil. With the aim of determining the stabiliser optimal content in the mixture with the soil, in the first part of the research, the effects of stabilisation of clayey soil of medium plasticity using the considered stabilisers with different percentage share on the change in uniaxial compressive strength (UCS) and pH value of the soil at different time intervals after the treatment were analysed. In the second part of the research, additional tests were conducted on soil samples with optimal content for each of the considered stabilisers by monitoring changes in the physical and mechanical properties of the soil. These include Atterberg’s limits (liquid limit and plasticity limit), modulus of compressibility in the oedometer, California bearing ratio (CBR), and swelling potential at different time intervals after the chemical treatment to determine the durability of stabilisation effects. The results of the conducted research reveal that each of the conventional, waste, and alternative materials considered as chemical stabilisers contributes to the improvement of the geomechanical properties of the clayey soil, primarily in terms of increasing the bearing capacity and reducing the swelling of the treated soil.

The unconfined compressive strength and shear strength represent the basic mechanical properties of clayey soil. If the soil in its natural state does not have sufficiently good mechanical properties, in engineering practice, it can be improved by chemical stabilisation of the soil. The stabilisation procedure involves adding reagent(s) to the soil with the aim of permanent improvement in the mechanical properties of the soil. In this study, the individual effects of seven different chemical stabilisers (traditional and alternative) on the mechanical properties of clayey soil were analysed. In the first stage of the research, comprehensive analyses were conducted on the effect of each of the selected stabilisers on the compressive strength of the soil. Each of the selected stabilisers was considered with three different content percentages in the soil mixture, with the aim of determining the optimal stabiliser content. Unconfined compressive tests were conducted to determine the unconfined compressive strength (UCS) of the soil. In the second stage of the research, extensive analyses of the effects of each of the selected stabilisers alone on the improvement in soil shear strength parameters (cohesion and internal friction angle), were carried out with the optimal content of each of the stabilisers. The shear strength parameters were determined by direct shear tests. Both stages of the research were conducted at three different time intervals after the chemical stabilisation (3, 14, and 28 days) in order to determine the long-term efficiency of the chemical treatment of clayey soil. Based on detailed comparative analyses, it was determined that all the selected stabilisers contributed to a lesser or greater extent to a significant improvement in the analysed mechanical properties of clayey soil. A statistical analysis of the obtained results was also conducted using the method of analysis of variance (ANOVA), on the basis of which the individual effect of each selected stabiliser on improving the mechanical properties of clayey soil was validated and quantified.

A number of current studies have revealed that during regular railway operations, different kinds of heavy metals accumulate on the track and in the railway body. Cadmium stands out among pollutants, both in terms of the amount of excess and in terms of the severe harm it causes to human life and health. In the first place, the study discusses existing methodologies for detecting the presence of heavy metals in soil on the railway body or in the surrounding areas. Following current procedures, the results of individual study were discussed and compared to those of other researchers. The individual study was done considering a section along a railway in service, which verified that cadmium was present on the railroad. In addition, various sources and origins of cadmium were analyzed considering the railway transportation. All the presented researches imposed an urgent need to establish effective remediation measures against the harmful impact of cadmium.

This study considered the effects of different types of additives on the physical and mechanical characteristics of clayey soil using a chemical stabilisation technique. Under laboratory conditions, samples of the clayey soil mixture with selected additives at percentages of 3 %, 5 %, and 7 % were prepared and tested at time intervals of 3, 7, and 28 d after the treatment. For the prepared samples, the influence of each additive on the change in the uniaxial compressive strength, Atterberg limits, and pH values was analysed. Based on the obtained results, the optimal amount of each additive for the treated soil was determined. Using the optimal additive contents, an additional series of tests to investigate the changes in the modulus of compressibility and void ratio of the treated soil were performed after 3, 7, and 28 d, as well as changes in the California bearing ratio and swelling value after 7 and 28 d. The obtained results reveal that, depending on the amounts of additives in the mixture and the time interval of the test, the physical and mechanical properties of the treated clayey soil could be considerably improved.