Geotechnical Characterization of Sub Grade Materials for Pavement Construction, A Case Study on Aposto – Wondo – Negele Road Upgrading Project, Contract 2: Irbamoda ~ Wadera Road Construction
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Date
2011-06
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Addis Ababa Universty
Abstract
Sub grade soils and materials characterizations are the main parameter for flexible
pavement both in the design and construction phases. Expansive soils in construction sites do
have significant influence on planning, structural design, construction and maintenance costs,
performance and engineering life of roads and highways. They are susceptible to considerable
volume changes in response to fluctuations in groundwater table and moisture content following
seasonal climatic variations. This property can cause severe damages to infrastructure unless
proper measures are taken in the design and construction phases. Identification of expansive soils
and characterization of their anticipated behavior is thus important for pavement structure &
drainage design, and estimating the cost, mitigating their undesirable properties. Hence to
mitigate the possible damages, sub grade soils and materials characterization have been
conducted.
The sub grade soils and materials characterization is conducted at Aposto ~ Wondo ~
Negele road upgrading project, contract 2: Irbamoda Wadera Road construction located in Adola
Rede woreda, Gujji Administrative zone of Oromia Region, The geographic locations for the
study area is bounded by UTM coordinates of 490698 E, 656488 N and 507644 E, 648577 N.
The main objectives of the study were: (1) to classify the sub grade soils in to homogenous
classes (2) to propose remedial measures for the unsuitable part of the sub grade soils and (3) to
propose alternative pavement thickness design.
To achieve these objectives, a total of 112 sub grade soils samples have been taken at
200m regular interval and tests are also conducted at project geotechnical laboratory for the
determination of Atterberg limits, grading, MDD and OMC, CBR and swell values.
Interpretations have been made with the data obtained from field works and laboratory
investigations, supported by previous studies and researches. In addition, geological data have
also been incorporated. From the laboratory investigation, it has been concluded that at least 82%
of the sub grade soils are found to be suitable for bearing stratum and construction materials.
Mechanical stabilization methods have been proposed for the unsuitable section. After evaluating
the pavement structure thickness conducted by the design review consultant, alternative
pavement design approaches have been forwarded. Based on the results and findings, certain
recommendations have also been given. These recommendations are removal and replacement,
in situ treatement, rock fill with geo textiles and underground drains
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IrbaModa ~ Wadera Road Construction