## 2 Basic Information on the Presented Case Studies
### Storage Facility (Landfill) of the Chemical Plant  
During several decades of operation of a chemical plant in Poland, approximately 360 thousand tons of waste were deposited in 10 landfills in its immediate vicinity. The waste was stored without any protection, which caused the penetration of hazardous  
Figure 1: Fragment of the unprotected storage site for chemical plant waste.  
substances into the soil and groundwater. After the chemical plant was closed, a decision was made to neutralize the waste by dismantling it and then installing it into an engineered landfill. In the case of one of the designed landfills, there was a need to improve a very soft waste (over 72,000 m\({}^{3}\)) in order to increase its shear strength. For this purpose, slag cement stabilization was used. For design reasons, it became necessary to determine the shear strength and unit weight of the waste stabilized with 10% cement and its influence on the stability of the landfill. The strength parameters were obtained via direct shear tests and showed that the cement-stabilized waste is characterized by an angle of shear resistance equal to 32\({}^{\circ}\), cohesion equal to 25.9 kPa and a volumetric weight of 14.6 kN/m\({}^{3}\)[25]. Stability analysis was carried out using FEM analysis and the strength reduction method and showed that the stabilization of chemical waste with cement made it possible to deposit it safely in the engineered landfill [26; 27; 28; 29; 30; 31].  
The comprehensive decommissioning of the chemical plant involved, for example, demolishing the facilities and all installations, constructing an engineered landfill, including associated infrastructure, the removal of the existing waste storage areas, the treatment of contaminated groundwater, upgrading and operating the existing water treatment plant, and regulating the Stola river, including the revitalization of its glacial valley. The total amount of waste gathered at the plant, including the contaminated soil from underneath the dumping grounds, the contaminated soil from the plant grounds, the hazardous waste generated during the demolition and removal of processing installations, was estimated at about 1.5 million m\({}^{3}\)[32]. During the removal of waste storage area No. 5, after its dismantling but before its transfer to a properly secured engineered landfill, the waste was chemically stabilized at solidification points by mixing with a 10% slag cement (CEM II/B-S-32.5 R) addition, in order to improve its mechanical properties, particularly its strength. The waste was mostly like a very soft cohesive soil (Figure 2), and because it was stored in the form of tall embankments (up to 17 m), it was likely that it had lost its stability due to the formation of sliding surfaces crossing the waste embankment, as the waste was characterized by a near-zero shear strength.  
Figure 2: View of waste stored at area No. 5.  
As it is known, the stability of soil-made structures depends mainly on their strength and physical parameters, thus the need to strengthen the waste and to determine the angle of shearing resistance (\(\phi\)) and its cohesion (c) and unit weight (\(\gamma\)) values. In 2010-2011, at the Geotechnics and Roads Department of the Silesian University of Technology, a study was conducted to determine the above strength and physical parameters of waste stabilized chemically with slag cement (CEM II/B-S-32.5 R) added at a 1:10 weight ratio, for the purpose of neutralizing about 72,000 m\({}^{3}\) of chemical waste.