How to Construct Low Cost Road(Cheap Road)? | Types, Advantages & Disadvantages
Table of Contents
What is Low Cost Road?
The road constructed and maintained at a low cost by utilizing the locally available materials & labours is low cost road. It is also referred to as a cheap road.
Where Low Cost Road is used?
In the villages and underdeveloped areas, immediate need of road can be fulfilled at low cost by these roads and can be improved further if required in the future.
This is the best choice for underdeveloped areas where the investment fund is smaller.
What is the main aim of this road?
The main aim of constructing the low cost road is to minimize the cost of construction. So, the use of heavy machines should be minimized and priority should be given to the local materials and labours.
1.1. Types of Low Cost Road
How many types of Low Cost Road are there?
There are four types of low cost road:
1)Earth Road
2) Kankar Road
3) WBM Road
4)Gravel Road
1) Earth Road
What is an earth road?
The road that is totally constructed from the soil available at the site (or road alignment) is earth road.
The earth used in this road may be either natural earth or stabilized earth.
How many types of earth roads are there?
There are 2 types of earth road naming Ordinary Earth Road & Stabilized Earth Road.
If natural earth is used in the construction of earth road then it is ordinary earth road.
If stabilized earth is used in the construction of earth road then it is stabilized earth road.
The road that is constructed utilizing kankar or chips of impure limestone is Kankar Road.
When kankar road is constructed?
It is only constructed when limestones are available in sufficient quantity.
3) WBM Road
What is WBM Road?
WBM road is the pavement whose surface course is made up of crushed or broken aggregates that are mechanically interlocked by rolling and voids are filled using filler materials with the assistance of water.
It is a type of unpaved road that is surfaced with gravel which has been brought to the site from a quarry or stream bed.
This road is common in less developed nations, and also in rural areas of developed nations.
1.2. Construction of Low Cost Road
The construction of low cost road includes the following steps:
a. Alignment Selection
The alignment shows the path through which the road will pass. So, the selection of road alignment should be done such that it has less conflict, high soil strength & shorter length.
Road alignment is the key factor that directly influences the construction speed and economy.
b. Cutting & Filling of Earth
Cutting and filling work is carried out to provide proper shape to the road.
During this process, if the side slope is unstabilized then retaining wall of wooden logs is provided. In the absence of wooden logs; locally available stones are used.
c. Preparation of Sub-grade
Sub-grade preparation involves the process of compaction of the soil to increase strength, stability and bearing capacity.
Compaction of sub-grade should be done with the assistance of water.
Road strength is determined by sub-grade. So, the subgrade should be compacted multiple times (according to the type of soil).
d. Preparation of Pavement
Above the subgrade, a layer of material is provided which acts as both base and surface course.
Road Type
Pavement Material
Earthen Road
Earth
Kankar Road
Kankar
WBM Road
Crushed Aggregate
Gravel Road
Gravel
The pavement layer is also compacted as similar to sub-grade with the assistance of water.
f. Drying
The road is allowed to dry naturally for 1 to 3 days and then opened to traffic.
Note: If the soil(subgrade) strength is high; the pavement thickness may be reduced to reduce the cost of construction.
1.3. Considerations in Low Cost Road
Following construction practice should be reviewed for low-cost road construction:-
1) The road shall be constructed on a balanced approach following the mass curve.
2) The road shall be constructed in stages.
3) Local materials shall be used.
4) Local manpower should be utilized.
5) Planning shall be done in a decentralized manner.
6) Bio-engineering shall be practised for slope stability (instead of costlier structure).
7) Cross slope of the road shall be towards the outside. so, as to avoid the side-drain.
8) In the case of natural water resources; causeway shall be preferred instead of bridges, culverts or other costlier construction.
9) The garbage wall and wooden log wall shall be preferred instead of retaining wall.
