low cost road l earthen road

Low Cost Road (Cheap Road) | Construction | Advantages & Disadvantages

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A low cost road is a road that is constructed and maintained at a low cost by utilizing the locally available materials & labours. It is also referred to as a cheap road.

In the villages and underdeveloped areas, immediate need of road can be fulfilled at low cost by these roads and these can be improved further if required in the future. 

This is the best choice for an underdeveloped area where the investment fund is smaller.

The main aim of 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.

 

Types of low-cost road

There are 4 types of low-cost road. They are:

1)Earthen Road

2)Soil stabilized Road

3)WBM Road

4)Gravel Road

 

1)Earthen Road

The earthen road is the cheapest type of road. The pavement structure is constructed totally from the soil available at the site. It is advantageous if we have to construct the road at the limited fund and this road may further needed to be improved in the future for an increase in traffic volume. This type of road is generally found in village areas.

 

2)Soil Stabilised Road

The process of soil stabilization refers to changing the physical properties of soil to improve its strength, durability, or other qualities. Hence, a road constructed using such stabilized soil is called soil stabilized road.

 

3)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.

 

4)Gravel Road

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. They are common in less developed nations, and also in rural areas of developed nations.

 

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 addition of a suitable amount of water.

In another word; sub-grade is the foundation of the road. Hence, road strength is determined by sub-grade. So, it should be compacted multiple times (according to the type of soil).

 

d. Preparation of Base Course

There are four types of low-cost road and they have their way to prepare their base course. Most commonly; base course consists of stone chips and earth. The base course is also compacted as similar to sub-grade with the addition of a suitable amount of water.

 

e. Preparation of Surface Course

Earth is used as a surface course in the earthen road and crushed aggregates are used as a surface course in WBM road.

Gravel acts as a surface course in gravel road & stabilized soil acts as a surface course in stabilized soil road.

 

f. Drying

The road after preparation is allowed to dry naturally for 1 to 3 days and then opened to traffic.

 

Note: If the soil strength is high; the base course may be avoided to reduce the cost of construction.

 

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.

 

Advantages of Low cost road 

Some of the advantages of the low-cost road are:

1)No large investment of capital is required initially.

2)Local people and materials are utilized.

3)As bio-engineering is preferred for slope protection. It is more environment-friendly.

4)Stage construction technique helps to manage the dispute arises at the construction site.

5)The cost of side drain construction can be saved.

6)It helps to mobilize rural materials.

7)It can be upgraded to blacktopped road economically.

 

Disadvantages of Low Cost Road 

Some disadvantages of low cost road are:
a. Not suitable for heavy traffic.
b. The requirement of maintenance after heavy rainfall.
c. Low comfort & high vehicle operation cost.

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