Appendix C 4.5 Seal Design
A summary of the seal design is provided in Table C 6.
Table C 6: Design calculations
| Attribute | Symbol | Units | 1st Application (14 mm) | 2nd Application (7 mm) | Shoulders (7 mm) |
|---|---|---|---|---|---|
| Traffic | – | AADT | 2000 | 2000 | See Table 5.2 |
| Design traffic | – | v/l/d | 1000 | 1000 | Adopt < 100 |
| Basic voids factor | Vf | – | 0.13 (Figure 6.4) | 0.16 (Figure 6.4) | 0.21 (Figure 6.1) |
Adjustments: Aggregate shape Traffic effects Other | Va Vt – | L/m²/mm L/m²/mm L/m²/mm | –0.01 (Table 6.1) –0.02 (Table 6.2) Nil | 0.0 (Table 6.1) –0.02 (Table 6.2) Nil | 0.0 (Table 6.1) 0.02 (Table 6.2) Nil |
| Design voids factor Vf + Va + Vt | VF | L/m²/mm | 0.13 – 0.01 – 0.02 = 0.10 | 0.16 - 0.01 - 0.02 = 0.13 | 0.21 + 0.02 = 0.23 |
| ALD of aggregate | ALD | mm | 9.0 | 4.6 | 4.6 |
| Basic binder rate VF × ALD | Bb | L/m² | 0.10 × 9.0 = 0.90 | 0.13 × 4.6 = 0.60 | 0.23 × 4.6 = 1.06 |
| Binder factor | BF | – | 1.0 (Table 6.5) | 1.0 (Table 6.5) | 1.0 (Table 6.5) |
| Modified binder rate | Bbm | L/m² | 0.9 × 1.0 = 0.9 | 0.60 × 1.0 = 0.60 | 1.06 × 1.0 = 1.06 |
Allowances: Surface texture Binder Abs. by Agg. Binder Abs. by Pav. Embedment | Ast Aba Ap Ae | L/m² L/m² L/m² L/m² | + 0.4 (Table 6.3) Nil (Section 6.2.4) Nil (Section 6.2.4) Nil (Section 6.2.3) | N/A Nil (Section 6.2.4) N/A N/A | + 0.3 (Table 6.3) Nil (Section 6.2.4) Nil (Section 6.2.4) Nil (Section 6.2.3) |
| Design binder rate Bbm + Ast + Aba + Ae | Bd | L/m² | 0.9 + 0.4 = 1.3 | 0.6 | 1.06 + 0.3 = 1.36 Adopt 1.4 |
| Aggregate spread rate | – | m2/m3 | 950/ALD = 105.5 (Table 6.11) Adopt 105 | 900/ALD = 195.7 (Table 6.12) Adopt 195 | 900/ALD = 195.6 (Table 6.11) Adopt 195 |
The final step of the seal design is to apportion the geotextile binder retention allowance to the design binder application rates.
The bond coat will be applied at 0.5 L/m2.
The remaining 0.7 L/m2 of the binder retention allowance is added to the binder design rate of the first layer of the seal as follows:
First layer binder application rate = binder design rate + remaining geotextile binder retention allowance
= 1.3 + 0.7
= 2.0 L/m2.
The second layer of the double/double binder is applied as designed in Table C 6.
Additionally, all longitudinal joints of geotextile reinforced seals are overlapped. Guidance for overlapping is provided in Austroads (2014b).