# CPT Parameters of Loess Subsoil in Lublin Area
## 4 Discussion  
The obtained results allowed the authors to characterize loess soils from the Lublin area. Cumulative data from soundings are presented in the diagram (Figure 10), while Table 2 includes characteristic values of each loess facies. The analyzed data show that the vast majority of loess soils belong to the aeolian facies and its parameters were crucial for the foundation of building structures. The highest \(q_{c}\) values were obtained for this facies. Figure 8: Summary of results for the aeolian facies: (**a**) distribution of \(q_{c}\) values and (**b**) sounding parameters plotted against [PERSON]’s chart (1—sensitive fine grained; 2—organic material; 3—clay; 4—silty clay to clay; 5—clayey silt to silty clay; 6—sandy silt to clayy silt; 7—silty sand to sandy silt; 8—sand to silty sand; 9—sand; 10—grey sand to sand; 11—very silty fine grained; 12—sand to clayy sand; \(\rm D_{r}\)—density ratio; OCR—overconsolidation ratio; Sf—sensitivity factor; e—void ratio). Figure 9: Summary of results for the older aeolian facies: (**a**) distribution of qc values and (**b**) sounding parameters plotted against [PERSON]’s chart (1—sensitive fine grained; 2—organic material; 3—clay; 4—silty clay to clay; 5—clayey silt to silty clay; 6—sandy silt to clayy silt; 7—silty sand to sandy silt; 8—sand to silty sand; 9—sand; 10—grey sand to sand; 11—very silty fine grained; 12—sand to clayy sand; \(\rm D_{r}\)—density ratio; OCR—overconsolidation ratio; Sf—sensitivity factor; e—void ratio). The diluvial and alluvial facies occurred to a much smaller extent and the obtained results constituted a similar percentage. It should be borne in mind that diluvia were found in the upper parts of the subsoil and this zone was included in each sounding. Alluvia were most often found in the deeper parts of the subsoil and not all of the soundings covered this zone. The same applies to the older aeolian facies, the parameters of which were only examined in some of the tests. According to the authors, the particular facies of the loess subsoil in the Lublin area were distributed as follows: aeolian facies in a range from 75 to 80%, alluvial facies in a range from 8 to 15% and diluvial facies in a range from 8 to 10%. Most of the results obtained for the aeolian facies at the level of \(q_{c}\) in range from 4.5 to 8.0 MPa indicate that these soils were a good load-bearing substrate for building structures. Cone resistances mostly at the level of 1.5-4.0 MPa for the diluvial and alluvial facies confirm that these facies constituted less favorable foundation conditions. The reduced resistance results mainly from the increased water content in ground pores. This results in lower soil strength, but above all in increased deformability. Cone resistances \(q_{c}\) were the basis for the interpretation of the constrained modulus \(M\). It is especially the soils of the diluvial facies that provide unfavorable foundation conditions, as they occur near the surface. The deeper alluvia were partially consolidated by the soils lying on them. A common problem for loess is collapsibility [40; 41; 42; 43; 44]. Although this behavior is strongly associated with this soil, in practice it only affects a small part of it. According to the research by [PERSON] [25], collapsible loess soils are solid loess from the aeolian facies whose cone resistance is \(q_{c}\) < 3.0 MPa. This is an approximate criterion as the actual collapsibility test is performed with an oedometer. However, the oedometer test is