Serie II numero 81 - Dipartimento di Matematica e Informatica

ASSESSING RAIL TRACK SUB-BALLAST RESISTANCE THROUGH DENSITY TESTING: EXPERIMENTS 321
5. Experiments and results
Figures 12 shows the obtained results (the line of equality is dotted).
Note that it results:
And, then:
2,40
2,35
2,30
2,25
2,20
2,15
2,10
2,05
2,00
1,95
G G G G
mbparaffin
mbVSD
mbparafilm
mbgeom
Vmbparaffin VmbVSD
Vmbparafilm
Vmbgeom
DGFC (NMAS = 10 mm)
Gmb(parafilm) Gmb(VSD) Gmb(paraffin)
y = 0,8731x + 0,3633
R 2 = 0,9909
y = 0,9673x + 0,0915
R 2 y = 0,9525x + 0,1427
R
= 0,9845
2 = 0,9883
1,95 2,00 2,05 2,10 2,15 2,20 2,25 2,30 2,35 2,40
Gmb (geometric)
Figure 12
The following observations can be drawn (see figure 12): 1) the simplest
method (dimensional) and the Italian most used method (paraffin coated) have
the greatest distance (2% ~ 5%); 2) the other methods have a lower gap; 3)
many hypotheses should be proposed in the field of the “best descriptor”; it
remains quite unclear the assessment of the best Gmb indicator; research is still
needed on this topic.
Main findings
In the light of the above, the following conclusions may be drawn:
1) research prove that HMA layers in rail track sub-ballast can have an
outstanding importance.
2) bulk volumes estimated by the dimensional method are greater than that
estimated by the parafilm, VSD (Vacuum Sealing Device) and paraffin method;