## 4 Discussion of the Obtained Results  
### Peculiarities of Dynamic and Static Waterjet Stimulation  
Based on the obtained results of the first series of experiments, it is concluded that the design of waterjet nozzles No.1 and No.2 allows for effective disintegration of the aerated concrete block sample--deep point channels were created, which facilitated making a through channel. However, the diameter of the created channel is not enough to fully accommodate the equipment assembly. This conclusion is explained by Figure 7.  
In addition, based on Figure 4 the authors can conclude that increasing the number of diffusers on the front part of the waterjet nozzle helps increase the diameter of the created channel (coverage by waterjet drilling). However, this reduces the efficiency of the drilling process itself, as nozzles No.3 and No.4 do not create a through channel. Therefore, the authors assume that it is necessary to estimate the ratio of specific flow rate of the working agent to the unit of total area of both front and rear diffusers. Table 3 shows the calculation of the aforementioned specific flow rate of the working agent for the considered types of through-type waterjet nozzles. Exact determination of the value of optimal specific flow rate of the working agent for different types of rock remains open and requires additional bench tests; however, given the current results, we can already make an unambiguous conclusion that it is necessary to consider this parameter in the design of waterjet nozzles, as well as to use at least three diffusers on the front surface of the nozzle to ensure effective waterjet coverage. Thus, for effective disintegration of aerated concrete blocks, the ratio of specific flow rate of working agent to the unit of total area of front and rear diffusers should tend to 26.75 L/(min-mm\({}^{2}\)). Figure 6: Results of studying the effect of the size of the created radial channel on the speed of movement of the equipment assembly. Based on the results of the second series of experiments (Figure 3), the following conclusions are drawn:  
1. The dynamic mode of stimulation appears to be much more effective and high-performing in comparison with the static mode, because over the same period of time, the dynamic mode of operation resulted in a waterjet channel through which the waterjet nozzle can be advanced further. When the back-and-forth motion is created, the rock is cut and abraded. Also, the presence of a constantly changing distance between the nozzle and the frontal wall of the created channel makes a significant effect in the destruction of the rock in front of itself. In the case of static impact, the hydromonitor nozzle is tightly pressed with the frontal part into the rock, which does not allow the front jets to cover a large cross-sectional area of the created channel. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Waterjet Nozzle** & **Number of Diffusers on the** & **Number of Diffusers on the** & **Specific Flow Rate of the Working** \\
**Arrangement No.** & **Front Part/Diameter of One** & **Rear Part/Diameter of One** & **Agent Per Unit of Cumulative** \\  & **Diffuser, mm** & **Diffuser, mm** & **Area of Front and Rear Diffusers,** \\ \hline
1 & 1/0.5 & 3/0.5 & 26.75 \\ \hline
2 & 1/0.5 & 3/1.0 & 8.23 \\ \hline
3 & 4/0.5 & 4/1.0 & 5.35 \\ \hline
4 & 4/0.5 & 6/1.0 & 3.82 \\ \hline
5 & 5/0.7 & 6/1.0 & 3.17 \\ \hline
6 & 5/0.7 & 6/1.2 & 2.41 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values of the calculated specific flow rate of the working agent per unit of the total area of the front and rear diffusers for the tested waterjet nozzles. Figure 7: Characteristics of created radial channels in static mode of waterjet stimulation: (**a**) when using waterjet nozzle No.1; (**b**) when using waterjet nozzle No.2. Thus, the required channel expansion does not occur so that the hydrodynamic nozzle can move forward and connect the rear jets to the channel expansion process. 2.