# CPT Parameters of Loess Subsoil in Lublin Area
## 1 Introduction
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Granular Type** & & **Facies Type** & & **Landform Type** \\  & **of the Loess** & & **of the Loess** & & **of the Loess** \\ \hline  & & - & aeolian & & \\ - & clayey loess & - & aeolian–diluvial & - & interfluve loess \\ - & silty loess & - & aeolian–colluvial & - & slope loess \\ - & sandy loess & - & aeolian–limnic & - & valley loess \\  & & - & aeolian–alluvial & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Division of loess according to [PERSON] [2]. Figure 1: Ideogram of the facial–genetic division of loess [2]. favorable among all loess materials. However, the phenomenon of collapse may still occur within this facies [2; 5; 6; 12]. The second facies representing the Lublin subsoil is aeolian-diluvial loess soils, which are characterized by less favorable geotechnical parameters. This is mainly due to the action of postgenetic factors, especially in the form of rainwater, rinsing and washing the aeolian sediment into the lower parts of the slopes. On large plains without a clear slope of the terrain, diluvia are evenly distributed in the subsurface layers of the subsoil. On hilltops, they form enclosed depressions, which during periods of long rainfall show the ability to retain water, while losing the features of a load-bearing soil. Within this facies, the content of the clay fraction is increased, which makes these loess soils more clayey. This facies also occurs in deeper parts, sometimes separating the typical younger aeolian loess from the older ones. In the upper part of older diluvia, which used to be the topsoil, traces of organic matter can also be encountered, they are the so-called paleosols [2; 5; 6; 12]. Another facies found in Lublin is the aeolian-alluvial valley loess. This facies was formed as a result of the sedimentation of wind-transported silt in water conditions and the redeposition of older aeolian sediments and diluvia. It is located mainly in river valleys, old denudation and erosion valleys. It is characterized by brick-yellow, yellow-grey or grey color. It contains numerous beds in it and it is sometimes lithologically heterogeneous. In terms of particle size distribution, it should be classified as clayey silt and silty clay, with a significantly higher content of clay particles compared to aeolian loess (up to 20%) [2; 5; 6; 12]. Loess soils cover over 50% of Lublin's area and determine the geotechnical conditions of the left-bank basin of the Bystrzyca River. In the Lublin region, they cocerate a foundation soil with usually favorable geotechnical parameters; however, an analysis of local conditions is necessary. Currently, one of the most popular field studies is CPT static sounding, which due to its specificity provides rich quasicontinuous data at depth. It makes it possible to examine the soil profile to considerable depths, to derive many geotechnical parameters of the soil from the measured values, and at the same time it remains a relatively economical and quick test [13; 14]. CPT sounding is currently the most universal soil test and there are numerous correlations both for deriving soil parameters from the data recorded during the test and for recognizing the type of soil [14; 15; 16; 17; 18; 19; 20]. In Poland, [PERSON]'s SBT (soil behavior type) [21] chart is widely used for the interpretation of soil type, modified and adapted to Polish conditions by [PERSON] et al. [22]. The results presented in the article add new data to the documented knowledge. The results of field studies and guidelines for conducting them on the loess of the Lublin region have been described in publications [23; 24; 25; 26; 27], and the data from soundings are the basis for determining soil parameters [17; 28; 29; 30; 31] and engineering calculations [12; 32; 33]. In the light of the above, linking the numerical results of CPT static sounding to the genesis of loess will bring significant benefits to geotechnicians and engineering geologists in terms of data interpretation.