## 3 STF-Based Stemming Material
### Rheology Tests for STF-Based Stemming Materials  
STF samples were placed between a cone plate and the foundation support of the rheometer for testing using an Austrian rheometer, Anton Paar MCR301. The shear rate of the sample was gradually increased from 0 to 100 s\({}^{-1}\) during the experiments conducted at 25 \({}^{\circ}\)C. Figure 5a,b display the schematic of the rheometer and the results of the tests on STF-based materials, respectively. The trials revealed a shear-thickening effect at a shear rate of 85 s\({}^{-1}\). As the shear rate increased, initially, there was shear thinning in the STF, which later intensified. Notably, as the shear rate attained a critical value, the viscosity of the STF abruptly increased, indicating a shear-thickening phenomenon. However, after some time of experiencing thickening behavior, there was a drop in viscosity. The maximum viscosity observed for the STF sample was 525 Pa, with a shear rate of 85 s\({}^{-1}\).  
Figure 4: Diagrammatic representation of STF’s shear-thickening mechanism.  
Sand is the most commonly used material for stemming in blasting operations. In this study, the stemming material used for the blasting experiment was common sand with an average particle diameter of 0.52 mm, as shown in Figure 6a, and the STF-based stemming is illustrated in Figure 6b. The particle size sieving curve and properties of the sand used in the experiment and analysis are listed in Table 2.  
Figure 5: (**a**) The rheometer schematic [24] and (**b**) the material rheological characteristics derived from STF analysis [25].  
Figure 6: Stemming materials for blasting experiments. (**a**) Sand and (**b**) STF-based stemming.  
When a hammer struck the surface of a mixture called shear-thickening fluid (STF) made up of starch particles ranging from 5 to 20 \(\upmu\)m suspended in water, it behaved as if it was a solid surface. To maintain the shear-thickening property and keep the solution workable, an STF blend with a 55% weight concentration was prepared using both ultrasonic agitation methods, described in reference [26]. Experiments with maize starch concentrations between 52.5% and 55% showed that objects bouncing off the suspension's surface reacted similarly to hitting an object, as explained in reference [27].  
Furthermore, the studies referenced in [28; 29] found a link between shock wave velocity and STF behavior by utilizing laser-induced shock tests to draw their conclusions.  
To illustrate the application of the Hugoniot power series, one can calculate the power series expansion for the linear relationship between shock wave speed (\(u_{s}\)) and particle velocity (\(u_{p}\)), within the context of STFs.  
The basic equations that describe how STFs behave during shock situations, including the principles of mass and momentum conservation as the specified linear relationship between velocities \(\left(u_{s}-u_{p}\right)\), are detailed in Equations (5)-(7) accordingly.  
\[\rho_{0}u_{S}=\rho\big{(}u_{S}-u_{p}\big{)}, \tag{5}\]  
\[P_{H}=\rho u_{S}u_{p}, \tag{6}\]  
\[U_{S}=C_{0}+Su_{p}, \tag{7}\]  
where \(u_{s}\) is the shock speed, \(P_{H}\) is the Hugoniot curve pressure, \(\rho_{0}\) is the density, \(S\) is the linear coefficient, \(u_{p}\) is the particle velocity, and the starting-state velocity of sound is represented by \(C_{0}\).  
Table 3 is a list of the STF's relevant constitutive parameters. It is noteworthy that the creation and collapse of cavitation bubbles in fluids are not described by the Mie-Gruneisen equation of state (EOS). Cavitation, however, is difficult to achieve in fluids with exceptionally high viscosities, such as the STF utilized in this investigation.