Components of a Hill Road
Following 7 component of a hill road are described below
1. Retaining Walls
➤ Retaining walls are the most important structure in hill road construction. It provides adequate stability to the roadway & to the slope.
➤ Retaining walls are constructed on the valley side of the roadway.
➤ Retaining walls are constructed in stone masonry, brick masonry or cement concrete. But usually dry stone masonry is adopted as it permits easy drainage of seepage water and also it is economical.
➤ The height of a dry stone masonry retaining wall is restricted to 6 m. When the height of the wall is more than 6 m bands of coursed rubble masonry in cement mortar are constructed after every 3 m height.
➤ The function of this wall is to resist the pressure of earth filling.
2. Brest Walls
➤ Breast walls are constructed to support the uphill slopes of the road cross-section.
➤ This wall is constructed when the Hill side is steep and there is a tendency of it’s sliding down towards the road.
➤ Brest walls are constructed in stone masonry, brick masonry or cement concrete.
3. Catch Water Drain
➤ A drain provides higher up on the hill slope side, running parallel to the roadway is known as catch water drain.
➤ The function of these drains is to intercept & divert the water from the hill slope.
4. Parapet Wall
➤The wall provided above the formation level of a hill road, usually towards the downslope side is known as the parapet wall.
➤This wall provides protection to the traffic against falling down the hill slope. This type of wall is not constructed as a continuous wall but with suitable gaps in between for economy in its construction.
5. Weep Holes
➤ The holes provided in a retaining structure such as retaining wall, breast wall, abutment, etc to drain off the seepage flow are known as weep holes.
➤ These holes are 8 to 12 cm in diameter or square in section. They are provided @ 1.2 m centre to centre in a staggered fashion.
6. Hairpin Bend
➤ The curve in a hill road which changes its direction through an angle of 180 or so is known as hairpin curve and the bend formed at the hairpin curve is called the hairpin bend.
➤ This type of curve should be located on a hill side having the minimum slope and maximum stability. It must also be safe from land sides & groundwater.
7. Cliff Galleries
➤ Cliff galleries are temporary roadway for short term used. When the time available for blasting and tunnel work is insufficient, cliff galleries are constructed for the negotiation of cliff (steep rocks)
➤ These are suitable only light vehicles or foot traffic and considered only for short term use & not as a permanent Roadway for regular traffic.