## 6 Conclusions  
This paper is concerned with the analysis of changes in the granulometric composition of silty sand samples through a procedure comparing the values of the silt and clay fraction \(f_{Si+Cl}\) in the structure before and after SHPB experiments using a laser diffraction particle size analyzer. Two types of non-cohesive soil-silty sands were selected for testing. The optimum moisture contents \(w_{opt,1}=8.70\%\) and \(w_{opt,2}=9.20\%\) were determined for both reference samples (tests carried out using the Proctor method), and the silt and clay fractions \(f_{Si+Cl,1}=15.14\%\) and \(f_{Si+Cl,2}=20.48\%\) were determined (tests carried out using a laser diffraction particle size analyzer, assuming a boundary value of 63 \(\upmu\)m between the sandy fraction \(f_{Sa}\) and the silty fraction \(f_{Si}\)). During comparative analysis of the test results, repeatable trends in changes in the granulometric composition of soil samples were noted:  
* Each dynamic impact with the bar projectile results in an increase in the value of the silt and clay fraction \(f_{Si+Cl}\) (there is a phenomenon of destruction of the soil skeleton through the breaking of grains and an increase in the percentage of grains with a smaller diameter). * As the value of the initially applied pressure of the pneumatic launcher to start the bar projectile movement increases, there is a noticeable trend towards an increase in the proportion of the silt and clay fraction in the granulometric composition of the sample. * For soil samples with a moisture content of \(w_{1}=0\%\) and \(w_{2}=5\%\) (values below the optimum moisture content of \(w_{opt,1}=8.70\%\) and \(w_{opt,2}=9.20\%\) depending on the type of sample) for a given initial pressure of the pneumatic launcher, a tendency towards an increase in the values of the silt and clay fraction is apparent (there is no significant effect of water on the test results). The higher the moisture content of the soil sample (in particular for values \(w_{3}=10\%\) and \(w_{4}=15\%\) above the optimum moisture content \(w_{opt,1}=8.70\%\) or \(w_{opt,2}=9.20\%\) depending on the type of sample), the stronger the trend towards a decreasing value of the silt and clay fraction in the granulometric composition of the silty sand sample. There is a noticeable dynamic response of the water filling the soil pores--the water gives the sample the characteristics of an elastic material and \"dampens\" the dynamic impact of the bar projectile. This interaction of water in the sample has the effect of reducing the destruction of the soil skeleton through grain fracture. * For the first type of soil sample \(f_{Si+Cl,1}=15.14\%\), the most significant is the bar projectile impact at an initial launcher pressure \(p_{2}=1.8\) bar for all sample moisture contents variants \(w_{1}\div w_{4}\)--at this pressure \(p_{2}\), the greatest percentage change in granulometric composition occurs through an increase in the value of the silty and clay fraction \(f_{Si+Cl,1\cdot k}\) relative to the reference sample \(f_{Si+Cl,1}\). On the other hand, for the second type of soil sample \(f_{Si+Cl,2}=20.48\%\), the greatest percentage change in granulometric composition occurs with a bar projectile impact at an initial launcher pressure \(p_{3}=2.4\) bar for all moisture content variants \(w_{1}\div w_{4}\)--at this pressure \(p_{3}\), the greatest percentage change in granulometric composition occurs through an increase in the value of the silty and clay fraction \(f_{Si+Cl,2\cdot k}\) relative to the reference sample \(f_{Si+Cl,2}\). Conceptualization, K.S. ; methodology, K.S. and R.C. ; formal analysis, K.S. and R.C. ; investigation, K.S. ; resources, K.S. and R.R. ; data curation, K.S. and R.R. ; writing--original draft preparation, K.S. ; writing--review and editing, K.S., R.C. and L.K. ; visualization, K.S. ; supervision, R.C. and L.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding. **Infrared Consent Statement:** Not applicable.