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.

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.

Clayey soil in its natural state usually has a low bearing capacity, high compressibility, and high sensitivity to changes in water content. These properties represent an obstacle to the use of this type of soil in construction industry projects, so it is necessary to stabilize it before its application for construction purposes. This paper presents the results of a comparative study of the effects of chemical stabilization of clayey soils on improving soil properties by considering a variety of chemical reagents. In addition to commonly used chemical reagents such as calcium carbonate (lime), alternative materials such as magnesium carbonate, sodium silicate, and potassium hydroxide were also considered. With an aim to determine the optimal content of reagent in a mixture with clayey soil, each of the selected chemical reagents was considered with three different percentage shares in the mixture. Given that the permanent improvement of soil properties is of utmost importance in geotechnical engineering, for this purpose, changes in the crucial physical and mechanical properties of the treated clayey soil (Atterberg limits, unconfined compressive strength, and shear strength) were also monitored over time after the chemical treatment. The research results revealed that the selected chemical reagents have different efficiencies on the considered physical and mechanical properties of clayey soil, whereby each of them contributed to the soil improvement. This opens up the possibility of applying the selected stabilizers within the framework of the chemical soil stabilization technique, primarily in the field of roadway construction.

Carrying out deep excavations in urban areas often involves complex geotechnical challenges due to the proximity of existing structures, infrastructure installations and requirements for limited deformations of the surrounding ground. For the purpose of building a new block within the Clinical Center in Užice, the design foresees two buildings with underground floors, for which it is necessary to construct diaphragms aimed at providing space for work. These structures enable effective prevention of the collapse of the side walls of the excavation and the groundwater inflow, while ensuring safe working conditions and maintaining the stability of adjacent structures. The paper presents the methods of designing and constructing diaphragms for the purpose of building a new block within the Clinical Center in Uzice, including the selection of dimensions, materials and construction methods, the interaction of the structure with the surrounding ground, as well as the challenges that had to be overcome in the above-mentioned stages.

As part of the reconstruction of the General Hospital in Užice, the construction of buildings marked C1 and C2 is planned. Given that the construction of these buildings, due to the planned underground floors, will involve deep excavations directly below Veselin Marinković Street, it was necessary to make a design for securing the foundation pits, as well as to perform a computational analysis of the stability of the terrain above the excavation area. The paper presents details of the computational analysis of slope stability, which was carried out in order to verify the impact of the designed reinforced concrete diaphragm for protecting the foundation excavation and structures C1 and C2 on the global stability of the terrain.