## 2 Materials and Methods  
### Study Area and Data  
The research was divided into three phases [1]. The first phase included a study conducted in 2014 where the blasting training area consisted of the two test boreholes PMB1 and PMB2, and eight boreholes, MB1-MB8 (Figure 2). The second phase was carried out in 2015 and consisted of the two test boreholes, PMB3 and PMB4, and 24 boreholes, MB13-MB36 (Figure 2). The third phase was conducted in 2016 and consisted of the two test boreholes, PMB5 and PMB6, and nine boreholes, MB37-MB45 (Figure 2).  
The test boreholes were used to gain a better insight into the behaviour of the explosive charges of Pakaex and Permonex V19 used for this purpose and to define the length of the stemming. Based on the two test boreholes and eight boreholes from 2014, it was concluded that the best sand stemming is from 0.5 m to 1.00 m long.  
The spherical expansions of boreholes were created by the detonation of the Ammonia Nitrogen Powder Explosive Permonex V19 and ANFO explosives commercially known as Pakaex. The velocity of detonation (VOD) is a detonation parameter that can be used to determine the performance of used explosive in different rock types also in a coherent clay. The basic characteristics of Pakaex explosive charge are density 0.87 g/cm\({}^{3}\), VOD 2950 m/s, and gas volume 984 L/kg, and of explosive charges Permonex V19 are density 0.95 g/cm\({}^{3}\), VOD 4500 m/s, gas volume 900 L/kg. Furthermore, it should be noted that during the research, the boreholes PMB4, MB33, and MB30 were destroyed, by the work of mechanization in the exploitation field Cukavec II [3].  
As a result, data on the type and length of the borehole stemming (S[m]), the explosive charge mass (Q[m]), the volume of the resulting cavity (V\({}_{\text{rc}}\) [m\({}^{3}\)]), the resulting expansion of the borehole (L\({}_{\text{rc}}\) [m]) and the deepening of the resulting expansion (D\({}_{\text{rc}}\) [m]) (Figure 3) was obtained. The data of spherical cavity blasting for explosives Pakaex and Permonex V19 are shown in Table 1. Based on the data displayed in Table 1, the volume of the resulting cavity, V\({}_{\text{rc}}\) [m\({}^{3}\)], and resulting expansion of the borehole, L\({}_{\text{ne}}\) [m], at the same explosive charge mass, Q [kg], were higher after the activation of Permonex V19 than Pakaex because Permonex V19 has a higher density and VOD. Moreover, deepening of the resulting expansion, D\({}_{\text{rc}}\) [m], at the same explosive charge mass, Q [kg], is larger with Pakaex than with Permonex V19.  
Obtained data was used to define resulting spherical cavity in clay after blasting, during which guidelines were given to geotechnical and builders on how the spherical cavity could be used in practice. The main effects of blasting in soils, particularly clay, are shown in the installation of structural elements for anchoring of foundations and retaining walls, permanent stabilization of clay slope and stabilization of various commercial structures such as overhead transmission towers, tunnels, etc. [2,3].  
The meteorological input data in the form of daily precipitation, minimum and maximum daily air temperature, and relative humidity was acquired from Croatian Meteorological and Hydrological Service [26] in the form of tabular data, which was extracted and formatted as timeseries data suitable for input to ANN-s. The data was acquired for two gauges nearest to the exploitation site, main automatic station Varazdin, and climatological station Novi Marof.