# Additional Criteria for Playground Impact Attenuating Sand
## 3 Impact Attenuation Surface Sands
### High vs. Poor Performance IAS Sand--Typical Examples  
Figures 5 and 6 are provided to show the differences between a high performance IAS and a poor performance IAS sand.  
Figure 5 is the impact pulse versus time plot of a typical high performance IAS sand (Sand 04). It shows the asymmetrical g\({}_{max}\) plot (yellow trace) that is characteristic of sands (rather than the symmetrical plots that are observed with rubber and organic IAS). The plot has a steep leading edge and a more gradual trailing edge. The more gradual trailing edge occurs because the sand particles are flowing away from the impact site and thus allow the impact energy to dissipate. With a g\({}_{max}\) of 76.4 g (fail = 200 g) and a HIC of 218 (fail = 1000) it greatly exceeds the minimum performance requirements for use in children's playgrounds. This test was also performed 0.5 m above the maximum allowable  
Figure 4: IAS sand for a 3 m free height of fall for a fine sand that performed well when dry and failed when wet. The force-displacement curve plot for this sand (Dry Fine Sand @3 m Energy absorbed = 139 J, HIC = 364, within Figure 3).  
Figure 3: The force-displacement curves of six impact attenuation tests conducted using the UTS IAS testing device [32].  
playground equipment height (3.0 m). For this sand at 1000 impacts the coefficient of uniformity was less than 2.5, the fineness modulus was 3.16 and percentage fines was 1.0.  
Figure 6 is the impact pulse versus time plot of a typically poor performance IAS sand. It is the test results of calcareous sand that was being used as an IAS to protect playground equipment with a free height of fall of 3.0 m. It shows a 1469 HIC and a 201g\({}_{max}\) fail (yellow trace). It also shows both a steep leading edge and an almost vertical trailing edge for the acceleration pulse. This is indicative of little to no sand particle movement and energy dispersion away from the impacted area. This is an undesirable characteristic for children's playgrounds as it means the child is effectively impacting a rigid surface rather than one where the surface is semi-fluid and allows the energy to flow away from the impacted area.  
The near vertical trailing edge in Figure 6 is not typical of sand that provides fall attenuation. A typical IAS sand has a steep leading edge with a less steep trailing edge, as depicted in Figure 5.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Impact** & **g\({}_{max}\) (g)** & **j\({}_{max}\) (g/s)** & **HIC** & **At (ms)** & **t\({}_{end}\)** & **t\({}_{start}\) (ms)** \\ \hline
1 & 76 & 26,900 & 218 & 10.7 & 50.4 \\
2 & 178 & 164,000 & 569 & 4.4 & 21.2 \\
3 & 106 & 53,600 & 392 & 9.6 & 23.6 \\
4 & 173 & 87,000 & 665 & 4.3 & 19.6 \\ \hline \end{tabular}
\end{table}
Table 1: High performance IAS sand: Four successive impacts in the same location for a 3.5 m free height of fall. This sand passed and provided a critical fall height greater than 3.5 m where the free height of fall (equipment height) was only 2.2 m. Thus, providing the Hobart City Council with a safety margin of more than 1.3 m.  
Figure 5: High performing IAS sand for a 3.5 m free height of fall. This is the impact pulse versus time plot for impact 1 within Table 1.