## 1 Introduction  
Soil unit weight is a geotechnical parameter that is necessary to determine, among other things, the design bearing resistance of soils in drained conditions and the vertical component of geostatic stress. Nowadays, the basic and most reliable method to estimate this parameter is by direct tests conducted in laboratory conditions. However, these tests always require the highest quality samples with undisturbed structures, collection of which is very difficult, time-consuming and expensive. Alternative methods to determine the unit weight of soil in a direct way, in situ, using various types of penetrometers, mainly based on cone penetration test (CPTM) static probes, have been sought for a long time [1; 2; 3; 4; 5; 6]. Despite the widespread use of various types of penetrometers in engineering practice and the development of appropriate calculation formulas, their results have not always been strictly verified by laboratory methods; therefore, they cannot be treated as universal in relation to all types of soil, especially organic soil. Preliminary analyses in this area have shown that, at present, in relation to selected, locally-occurring, Polish organic soils, existing global relationships are of little use, and it is advisable to search for other, more accurate solutions [7].  
Alternatively, from a practical point of view, these methods seem to be designed to determine soil unit weight based on the research of samples with a disturbed structure; however, they are designed for soil with natural moisture, which is cheaper and relatively easier to collect. This is particularly important in the case of organic soils, which are extremely heterogeneous and have a locally diverse research medium. In addition, packages of organic soil are very often below the groundwater table, which makes it difficult, or even impossible, to collect samples of a sufficient quality with undisturbed structures. The data obtained from the testing of samples with disturbed structures of organic soils from local sites have these basic parameters: natural water content and organic matter content can be used to estimate the value of unit weight, while also regionalizing the parameters of a given type of organic soil.  
This paper presents a proposal to estimate the unit weight of various, local organic soils based on laboratory-determined leading parameters, as well as the results of alternative prognoses using artificial neural networks (ANN). In recent years, the application of ANNs in structural mechanics and civil engineering, including geotechnics, has increased. Examples of the use of ANNs in geotechnics in Poland can be found in the recent work presented by [PERSON] [8; 9; 10; 11; 12], [PERSON] [13], [PERSON] and [PERSON] [14; 15; 16] and others [17; 18; 19; 20; 21]. This paper shows the application of ANNs, in comparison to the standard regression.  
The choice of the ANN analysis tool was determined by the fact that it is a very universal tool that is increasingly finding an effective solution in the field of geotechnics [22; 23]. Artificial intelligence is used, among others, for soil classification [24], prediction of geotechnical properties [25], prediction of slope performance [26], calculations of the settlements of buildings and constructions [27], indirect estimation of rock parameters [28], the design and analysis of deep foundations [29], empirical design in geotechnics [30] or geomaterial modeling [31] and many other applications.  
Unfortunately, available source materials on the use of ANNs to predict the geotechnical parameters of organic soils for the practical design of foundations are rare and difficult to access, which was an additional argument to apply and verify the tool in this work.