Development of Road
Firstly Roman started construction of roads in large scale in 312 BC of length over 580 km.
Main features of roman roads are:
- They were built straight regardless of gradients.
- Total thickness of the construction was as high as 0.75 m to 1.2 m.
- They were built after the soft soil was removed and a hard stratum was reached.
- The wearing course consisted of dressed large stone blocks set in lime mortar.
- No cross slope is provided.
- No drainage system.
- Large foundation stones were provided at bottom.
Pierre tresaguet developed an improved method of construction in France during 1764 A.D.
Main features of Tresaguet construction are:
- Thickness of the road was order of 30 cm.
- Consideration was given to subgrade moisture condition and drainage of surface water.
- The sub-grade was prepared and a large layer of foundation stone are laid on edges which act as Kerb stone.
- The top wearing course was made up of smaller slope having a cross slope of 1 in 45 to the surface
- To provide surface drainage.
- Shoulder sloping was also provided of the order of 1 in 20 to drain the surface water to the side drain
His work started in early 19 century in England. In this also heavy foundation stones were provided above the soil sub-grade and cross-slope at top surface was given to ensure removal of the water.
Main Features of Telford Construction are:
- A level subgrade was prepared of width 9 m.
- Thickness of foundation stone varied from 17 cm to 22 cm at the center.
- A binding layer of wearing course 4 cm thick was provided with cross slope of 1 in 45.
- The central portion of about 5.5m width was filled with two layers of angular broken stones to compacted thickness of 10 cm and 5 cm.
Macadam Road differ from previous design in following aspect.
- Soil subgrade was also late at a cross slope 1 in 36 to avoid the seepage of water in it
- He was the first one to suggest that large foundation stones are not required to be placed at the bottom layer.
- Similarly the next layer of payment also constructed above this layer with broken stone of smaller size.
- The total thickness of construction was less but load distribution was comparatively better.
- The size Of broken stone at top was decided on the basis of stability under animals drawn vehicle.