## 2 Laboratory and CPTU  
Research was conducted on anthropogenic waste in the area known as the \"White Seas\" in Cracow. The \"White Seas\" area in Cracow is an approximately eighty-hectare site in which post-production waste from the Solvay Soda Works Plant was stored in the twentieth century. During the peak production period of the Krakow Soda Works Plant, up to 600 [Mg/day] of raw soda were produced, resulting in approximately 6000 [m\({}^{3}\)/day] cubic metres per day of post-production sludge (approximately 9-10 m\({}^{3}\) per ton of product) [21]. The decision to close the Krakow Soda Plant in 1989 marked the end of waste storage. Currently, most of the surface of the four soil pounds is covered with vegetation, except for  
Figure 2: Excavation during the construction of the Lagiewnicka route in the “White Seas” area (photo Pilecka). the northern pounds where the research was conducted. The locations where soil samples were taken for laboratory testing and the CPTU are shown in Figure 3 below. Laboratory tests were conducted on samples of anthropogenic soil collected at various depths in boreholes in order to determine the effective parameters. Typically, the determination of these strength parameters is conducted using triaxial compression apparatus [23; 24]. The first stage of the study involves saturating the soil sample. Saturation of the soil sample is necessary due to the measurement of pore pressure and changes in the volume of the soil sample. Only when fully saturated can the results of the study be reliably interpreted [23]. The second stage of the triaxial test is soil consolidation. This stage aims to achieve the desired level of effective stress in the test sample. The final stage of the study involves uniaxial compression of the sample in a triaxial state in the testing cell. By applying the loading scheme, it is possible to study the relationship between soil stress and strain. The tests were conducted on samples that were fully saturated, consolidated, and sheared under conditions allowing water drainage from the sample (Figure 4). The primary objective of the study is to determine the stress-strain characteristics. Based on the determined relationship, it is possible to determine the maximum shear stress  
Figure 4: Soil sample tested in triaxial compression apparatus (**a**) before the test, (**b**) after the shear, and (**c**) after the test (photo Zieba). Figure 3: Location of boreholes and CPTUs [22]. in the tested sample (shear strength). The most commonly used criterion for shearing a sample is the criterion of the maximum value of shear stress according to the Coulomb-Mohr condition. Under effective stress conditions, this criterion is presented as follows:  
\[\tau_{f}=\sigma^{\prime}\text{-}\tan\sigma^{\prime}+c^{\prime} \tag{2}\]  
where  
\(\tau_{f}\)--shear stress [kPa]. \(\sigma^{\prime}\), \(c^{\prime}\)--shear strength parameters, respective angle of friction [deg], and cohesion [kPa]. \(\sigma^{\prime}\)--effective stress [kPa], \(\sigma^{\prime}=\sigma-u\). \(\sigma\)--total stress [kPa]. u--pore water pressure [kPa]. The criterion for sample failure is described by strength parameters relating to the effective internal friction angle \(\varphi^{\prime}\) [deg] and effective cohesion \(c^{\prime}\) [kPa]. The determination of these strength parameters is performed by fitting a tangent to the Mohr circles. Based on the tangent's inclination, the friction angle can be determined, while the intersection point with the vertical axis allows for the determination of the cohesion value (Figure 5). In engineering practice, procedures enabling the determination of soil parameters based on CPTU results are commonly used [8; 9; 10; 25]. Example CPTU results from the tested anthropogenic soils are presented in Figure 6.  
To determine functional relationships with the laboratory parameters of the soils, normalised parameters from CPTUs are commonly used.