- 2066 Bhadra · 6 marks
Pavement classification; flexible layer functions
Short answer
Pavements are flexible, rigid, or semi-rigid. Flexible pavement layers: surface course resists wear and water, binder course spreads load, base course is main load-bearing, sub-base provides drainage and support, subgrade carries all load.
Classify pavement and explain the functions of different layers of flexible pavement.
Classification of pavements
Pavements are classified by how they transfer load to the subgrade.
- Flexible pavement - bituminous (or granular) surface over granular base and sub-base; the load spreads through grain-to-grain contact, with high stress near the surface and reduced stress on the subgrade. Examples: WBM with surface dressing, bituminous macadam, asphalt concrete (IRC:37).
- Rigid pavement - cement concrete slab (PQC) on a sub-base (DLC/GSB); the slab resists load by flexural strength and spreads it over a wide area (IRC:58). Types: JPCP, JRCP, CRCP, prestressed.
- Semi-rigid (composite) pavement - cement-treated or lean-concrete base with a bituminous surface; or concrete overlay on bituminous pavement.
By surface type, pavements are also divided into earthen, gravel, WBM, bituminous (surface dressing, premix, BM, DBM, BC) and cement concrete roads. Nepal DoR groups roads as paved (bituminous/concrete) and unpaved (gravel/earth).
Functions of layers of a flexible pavement
| Layer | Main functions |
|---|---|
| Surface (wearing) course | Resists tyre wear and abrasion, gives a smooth, skid-resistant and waterproof riding surface, protects layers below from water, takes the high compressive and shear stresses of the wheel |
| Binder course (DBM/BM) | Spreads load to the base, gives a stiff bituminous layer for fatigue strength, bonds the wearing course to the base |
| Base course (WBM/WMM/CTB) | Main load-bearing layer, distributes load to sub-base, provides drainage of the pavement and structural strength against shear |
| Sub-base (GSB) | Improves the support to the base, works as a drainage and filter layer, prevents intrusion of subgrade soil and capillary rise, saves costly base thickness |
| Subgrade (compacted soil) | The natural or improved soil (top 500 mm) that finally carries all load, so it must be compacted to at least 97 percent of Proctor density |
The thickness of each layer is fixed so that the stress reaching the layer below is within its capacity.
✓ Answer checked by Claude Opus 5.5 (high effort)
Related questions
- Pavement layer functions and rigid pavement joints · Transportation Engineering II, chapter 2
- Typical failures of flexible pavement · Transportation Engineering II, chapter 4 · asked 2×
- Flexible pavement design with 8 CBR values · Transportation Engineering II, chapter 2
- Flexible pavement life with 140 cvpd traffic · Transportation Engineering II, chapter 2
- Flexible pavement failures: causes and remedies · Transportation Engineering II, chapter 4
- Flexible pavement failures; deflection overlay design · Transportation Engineering II, chapter 4
- Materials in pavement layers · Transportation Engineering I, chapter 6
- Functions of data link layer · Computer Networks and Security, chapter 3 · asked 3×
- Functions of physical layer · Computer Networks and Security, chapter 2
- Functions of network layer · Computer Networks and Security, chapter 4