Assessment of Damages Caused by Expansive Soil on Roads Constructed in Addis Ababa
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Date
2022
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Addis Ababa University
Abstract
Roads are one of the basic infrastructures and serve as means of a communication system for any country.
The investment budgeted and the cost for original construction and repair of roads of our country is
relatively high.
Most of the time road lines constructed in our country failed early before functioning the design life. This
is because of various problems arising from different causes. Among these roads which are failing before
serving its design life is the Addis Ababa Roads. The main reason is that large areas of these roads are
constructed on problematic expansive soils. This is due to improper construction and operation of the road.
It is well known that Addis Ababa is a populated and investment area as it is the capital city of Ethiopia.
As a result, the roads in Addis Ababa serve or carry the highest daily traffic in the country. These roads
were constructed and opened to traffic in different years accordingly. The design pavement life was
estimated at 15 and above years, however; pavement structure failures have been observed since
construction time, within the first few years after opening to traffic.
From the end of construction to date, the Addis Ababa roads are repeatedly under periodic maintenance.
Considerable resources were spent during this period on periodic maintenance, but without solving the
basic problem. This maintenance is not working as each maintained section is failing within a short period,
hence, it needs to investigate the root causes of the failure to come up with an appropriate solution.
This paper tries to present some issues of geotechnical cases for roads built on expansive soils. Some case
study sites, representatives knew problem-areas in Addis Ababa were carefully selected for geotechnical
site investigation. The field exploration consisted of detailed observation and measurement of damaged
roads. These road damages have been identified and characterized based on the theoretical aspect of soil
property and its effect on construction. This work was also have been used any secondary data concerning
the study area as a baseline and it was helped as an input.
Field investigations which include visual condition survey, DCP test, Benkelman Deflection measurement,
and other methods were conducted to investigate causes of failure. Finally, based on the investigation, all causes of road failure are identified. Based on the identified damage
types and their causes, maintenance and rehabilitation mechanism or techniques are recommended and
suggested.
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Keywords
Pavement Failure, Condition Survey, CBR, Maintenance, DCP, Deflection