# CPT Parameters of Loess Subsoil in Lublin Area
## 1 Introduction  
Loess soils are found in many regions of the world and constitute the subject of research by geotechnicalians, geologists (often in terms of stratigraphy), paleopedologists and scientists from other fields [1, 2, 3]. These soils are aeolian deposits, formed as a result of the accumulation of dust particles of the soil moved by the wind. In macroscopic evaluation, loess is a relatively homogeneous, macroporous sediment, most often of a light yellow or beige color [4]. Polish loess soils are mostly composed of coarse silt (10-50 um). The clay and find sand fractions range from 5 to 25%. They contain an average of 60-70% of quartz and feldspars, calcium carbonate and dolomite in varying proportions. Loess soils are partially aggregated, with a porosity index ranging on average between 45% and 55% [5, 6]. The research approach to the study of loess deposits varies depending on the type of expected results. Many studies refer to particular features of soils without a detailed analysis of their genesis [7]. As a rule, loess soils were created by the wind transporting particles. However, very often other genetic processes, such as runoff, slide or accumulation through the action of water, occurred in parallel or later. Therefore, loess soils should be divided into facies taking into consideration their genesis, which has long been emphasized in the most important publications on loess [1, 2, 5, 8, 9, 10, 11]. According to the authors of the present publication, the clearest classification of loess is that proposed by [PERSON] [2]. Apart from the genetic-facies classification, [PERSON] also divides loess according to the grain size, distribution and topography. The three types of classifications he uses are listed in Table 1, while Figure 1 shows an ideogram illustrating the structure and division of loess deposits. When describing the genetic and facies variations, the protogenetic role of the wind is emphasized, therefore the name of each facies includes the word aeolian. However, it should be emphasized that genetic divisions should not be considered as rigid,but only as indicating the leading factor. Genetic processes often occur in parallel and are not always clearly identifiable. For example, diluvia are combined with colluvia, alluvia with diluvia or alluvia with limnic processes. As a result of additional processes shaping the subsoil, the influence of the protogenetic factor of the wind on soil properties decreases, and in the genetic context these deposits are often referred to as loses-like [2]. The variety of loess soils results from protogenetic, syngenetic and epigenetic processes, which, depending on the dominance of a given process, shaped their features and translated, among other things, into strength and deformability characteristics. Genetic processes are a very important element that should be taken into account in engineering research. The subsoil in the area of the Naleczowski Plateau, where Lublin is located, consists mainly of loess from aeolian and aeolian-diluvial facies, and in the deeper parts, from aeolian-alluvial facies. Aeolian (subaerial), so-called typical loesses, sedimented in dry periods and areas, are the dominant facies. In Poland, their formation is dated to the period of the Weichselian glaciation, but older loess soils are also found, which also occur in the area of Lublin. The subaerial loess covers usually have 90% of the silt fraction, and their characteristic color is yellow-grey, light brown or beige. They are located mainly on the uplands and partly on the slopes of valleys. They usually reach a thickness of up to 20 m, but locally they can reach even 30 m. The strength and deformability characteristics of this facies are the most