deterioration unsealed roads. 2 gravel earth (or sand) * unsealed roads classification * engineered...
Post on 03-Jan-2016
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6
Preservation• Routine
Off carriageway Grading Spot regravelling
• Periodic Regravelling
• Special Emergencies Winter maintenance
Development• Improvements
Widening Realignment
• Construction Upgrading New sections
Unsealed Road Work Classification
7
• Roughness:
Progression
Effect of mechanical compaction
Effect of grading
Average annual roughness
Steady state roughness
• Material Loss
Unsealed Roads Models
8
Roughness Without Compaction
0
5
10
15
20
25
30
0 1 2 3 4 5
Surface Age (years)
IRI
(m/k
m)
200 veh/day 100 veh/day 50 veh/day
10 veh/day
11
Long term average roughness
0
5
10
15
20
25
30
35
0 20 40 60 80 100 120 140 160 180 200
AADT
Ave
rag
e IR
I (m
/km
)
No grading
Grading 2 per year
Grading 4 per year
Grading 12 per year
12
Roughness: Effect of Grading Frequency and Traffic
Effect of Grading Frequency and Traffic on RoughnessFlat and Level Terrain / Sub-humid Environment
3
5
7
9
11
13
15
17
19
21
0 25 50 75 100 125 150 175 200 225 250 275 300
Average Daily Traffic (ADT)
Rou
ghne
ss (
IRI)
24 Months
18 Months
12 Months
9 Months
6 Months
3 Months
1 Months
GradingFrequency
13
Roughness: Effect of Terrain Type and Traffic
Effect on Terrain Type and Traffic on RoughnessGradings Every 6 Months / Sub-humid Environment
3
5
7
9
11
13
15
17
19
21
0 25 50 75 100 125 150 175 200 225 250 275 300
Average Daily Traffic (ADT)
Rou
ghne
ss (
IRI)
Mountainous
Hilly & Rolling
Flat & Level
TerrainType
14
Roughness: Effect of Environment Type and Traffic
Effect of Environment and Traffic on RoughnessGradings Every 6 Months / Flat and Level Terrain
3
5
7
9
11
13
15
17
19
21
0 25 50 75 100 125 150 175 200 225 250 275 300
Average Daily Traffic (ADT)
Rou
ghne
ss (
IRI)
Arid
Semi-arid
Sub-humid
Humid
EnvironmentType
15
Roughness: Effect of Material Properties
Lateritic Gravel Earth RoadSemi-arid Environment Semi-arid Environment
Frequency Flat & Rolling & Flat & Rolling &Traffic of Gradings Level Hilly Mountainous Level Hilly Mountainous(ADT) (months) Terrain Terrain Terrain Terrain Terrain Terrain
25 1 4.0 4.2 4.4 2.8 3.0 3.325 3 6.0 6.5 7.1 5.0 5.6 6.325 6 8.3 9.1 10.0 7.4 8.2 9.325 9 9.7 10.7 11.8 8.8 9.8 11.125 12 10.8 11.8 13.1 9.8 10.9 12.325 18 12.3 13.4 14.9 11.2 12.4 14.025 24 13.2 14.5 16.1 12.1 13.4 15.1
18
Road Roughness of Unsealed Roads
• Roughness equations valid for engineered unsealed roads with good maintenance (good drainage). Therefore:
Higher rainfall yields lower roughness Higher percent of trucks yields lower roughness Earth roads (finer soils) have lower roughness than
gravel roads, making difficult to evaluate regravelling works
• In practice, the condition of an unsealed road can be different from what is being predicted by the HDM models, specially related to the passability on the wet season
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