What is Earth Road ?
When the foundation and wearing surface of the road consists of one or two compacted layers of an ordinary soil or stabilized soil then such road is called as “Earth Road’
Types of Earth Roads :
There are mainly two types of earth roads :
- Ordinary Earth Road.
- Stabilized Earth Road.
Ordinary Earth Road :
When the foundation and wearing surface of the road is constructed by one or two compacted layers of a natural soil available along alignment of the road then such type of road is called as are the ordinary Earth Road.
Stabilized Earth Road :
When the foundation and wearing surface of the road is constructed by one or two compacted layers of stabilized soil it is called as stabilized Earth Road.
Different Terms Used in the Construction of Earth Road.
1. Borrow Pits :
Borrow pits are nothing but the pits dug Doug along the alignment of the road . They are generally dug to use the earth material from the pits for the construction of road embankment. Borrow pits should always be dug 5 meters away from the toe of the embankment.
2. Spoil Banks :
Spoil banks are generally constructed from excavated soil on the sides of cutting. They are generally constructed parallel to the alignment of road. Height of spoil bank should not be less than 1.5 m. Care should be taken that they are constructed 3 m away from top edge of cutting.
3. Lead :
At the time of construction of road soil is excavated to use it for the construction. The horizontal distance between the excavated earth and the point of placing that excavated soil is called as lead. Generally on site, 30 m lead is taken as initial for which contractors do not get any additional payments.
4. Lift :
Lift is the vertical distance of the lifting of excavated earth required for the construction. Generally on site, 15 m lift is taken as initial for which contractors do not get any additional payments.
5. Balancing Earth Work :
Excavation of earth is required for the construction process but at the same time balancing of the earth work is also recommended. There should be no large difference in the earth obtained from cutting to earth required for filling. To minimize this difference proper selection of gradient is required.
Construction Procedure of Earth Work.
There are only 2 materials required for the construction of earth road .Natural soil or the soil that is available locally and suitable stabilizer if required for the given conditions.
1. First of all proper survey of the site is done.selection of area for borrow pits is kept outside the land with of earth road. Center line is fixed and pegs are driven for reference of verticals profile of road.
2. Before excavation the site is totally cleaned from shrubs, trees, grass and other organic matter.
3. After the excavation process, the sub-grade of road is prepared. It is provided with sufficient camber and proper gradient. Generally the thickness of the pavement construction decides the depth of sub-grade.
4. After the preparation of the sub-grade it is properly compacted by rolling operation with the help of rollers. Sufficient amount of water is sprinkled along with rolling operation for proper compaction.
5. After the compaction another layer of graded soil is laid after sprinkling of water. The thickness of this layer is kept between 8-12 cm.
6. After the final work the camber of the earth road is properly checked and if found faulty it is then needed to be corrected.
7. After the construction of earth road, it is needed to be cured with sufficient amount of water for 4-5 days.
8. After proper curing is done the earth road is allowed to dry for minimum of 3 days and then it is opened for traffic.
Precaution to be Taken While Constructing Earth Road.
1. The camber to be provided in the construction of this road should be very steep i.e values from between 1 in 20 to 1 in 33 should be adopted.
2. To prevent the erosion of soil due to rain water, the maximum gradient should be 1 in 20.
3. To dispose off the rain water, the height of the embankment should be above 600 mm.
Advantages :
- The construction of earth road is a fast process.
- Proper selection of the gradient give balanced earthwork.
- In future if other type of road is going to be constructed on the existing earth road, it gives good foundation.
- The overall process is relatively cheaper than other road types.
Disadvantages :
- These roads are only useful for light traffic. It cannot sustain the lifespan of the road if it is allowed for heavy traffic.
- This type of road wears quickly and the maintenance is little bit costlier.
- This type of road cannot be constructed or it will be worthless in the areas where monsoon is on peak or areas that have maximum rainfall, as constant and excess rainfall lashes out these Kind of roads.
Also Read : WBM Road : Construction Procedure, Advantages and Disadvantages Also Read : Bearing Capacity of Soil and It’s Importance