Civil Engineering

Investigation to Ascertain the Causes of Failure and Present Traffic Capacity of Highways

Investigation to Ascertain the Causes of Failure and Present Traffic Capacity of Highways


The essence of this project work is to look into the causes of highway failure and the different types of failure which are presented along the Eliozu – New Airport road in Obio/Akpor L.G.A in River state, taken as a case study. Some factors identify as being responsible for the failure of the chosen road section includes, poor subgrade soil with questionable material. Ground water study is carried out, which give insight to it effect to the failure of the flexible pavement, lack of drainage facilities, improper pavement design, poor compaction and traffic volume increase and lack of maintenance are critically taken into consideration.

Traffic volume count and soil test analysis and test on asphalt such as extraction-gradation test, are properly carryout, of which it result gives an adequate insight to the various causes of the failure situation experience along the road section through this investigation, show that relative to pavement, base course, wearing course and sub base were to less than the requirement for effective functionality of the said road of case study. From the investigation carryout, useful recommendation are made to improve the design and proper ways of reducing the rate of failure in Nigerian highways.

Table of Content

Title Page
Table Of Content
List Of Tables
List Of Figure


1.1 Aims And Objective Of Study
1.2 Scope Of The Project Study
1.3 Background Information Of The Study Area
1.4 Limitation Of The Study


2.1 General
2.2 Engineering Properties Of Soil
2.2.1 Soil Properties As Highway Material
2.2.2 Highway Sub-Grade, Sub-Base, Their Thickness And Shaping
2.2.3 Material Classification American Assoication Of State Highway And Transportation Officials (Aashto) System Unified Soil Classification System (Uses)
2.2.4 Clay Soils And Their Engineering Properties
2.2.5 Soil Compaction And Consolidation Efficiencies
2.2.6 Soil Permeability And Compressibility
2.2.7 Ground Water Penetration And Its Effect On Road Bases
2.2.8 Effect Of Void In Highway Pavement
2.3 Types Of Pavement Distress
2.4 Traffic Survey
2.4.1 Interpretation Of Data
2.5 Traffic Capacity Studies
2.5.1 Factors Affecting Practical Capacity
2.5.2 Traffic Flow Characteristic
2.5.3 Traffic Volume Study
2.6 Relative Practical Terms
2.6.1 Site Exploration And Reconnaisance
2.6.2 Sourcing Of Samples
2.6.3 Measurement Of Pavement Thickness
2.6.4 Ground Water Inspection In The Location
2.6.5 Traffic Volume Study
2.6.6 Rainfall Data
2.6.7 Soil Tests Data
2.6.8 Soil Classification
2.6.9 The Californian Bearing Ratio (Cbr) Test Method
2.7 Classification Relation Terms
2.7.1 Effective Size
2.7.2 Uniformity Coefficient
2.7.3 Co-Efficient Of Gradation
2.7.4 Liqid Limit
2.7.5 Plastic Limit
2.7.6 Plasticity Index
2.7.7 Liquidity Index
2.7.8 Consistency Limit
2.7.9 Group Index
2.8 Aging Of Bitumen
2.9 Bituminous Mixes And It DesignPrinciples
2.9.1 Diagnosis Of Unsatisfactory Mixes Cases


3.1 Field Collection Of A Soil Sample
3.2 Colour Classification
3.4 Specific Gravity Test
3.5 Sieve Analysis
3.6 Atterberg Limit Test
3.6.1 Plastic Limit
3.6.2 Liquid Limit
3.7 Compaction Test
3.7.1 Standard Proctor Compaction Test
3.7.2 Modified Proctor Compaction Test
3.8 California Bearing Ratio (C.B.R) Test
3.9 Determination Of Water Table
3.10 Manual Method Of Traffic Count
3.11 Bull Specific Gravity Of Compactd Bituminous Mixtures Tests
3.12 Extraction-Gradation Test


4.1 Field Collection Of Soil Sample
4.2 Colour Classification
4.3 Natural Moisture Content
4.4 Specific Gravity Test
4.5 Sieve Analysis
4.6 Atterberg Limit Test
4.7 Classification Computation And Data Analysis
4.8 Compaction Test
4.8.1 Standard Proctor Compaction Test
4.8.2 Modified Proctor Compaction Test
4.9 Determination Of Ground Water Table
4.10 Manual Traffic Count Data And Analysis
4.10.1 Mean Daily Traffic
4.11 Tests For Bulk Specific Gravity Of Compacted Bituminous Mixtures
4.12 Extraction – Gradation Test


5.1 Conclusion And Summary
5.1.1 Summary
5.1.2 Conclusion
5.2 Recommendation


In construction of highway, generally the roads are not designed to last forever. It is been designed to serve some purpose for a specific time. As it can be seen in engineering work, the lifespan of a road is always an important factor that must be taken into consideration as one of the criteria for the construction. This really depends on the factors like construction procedure and consideration, the soil water relationship, quality of workmanship during the construction and the type of maintenance culture adopted.

Many roads (Highway mostly) are seen widely as attaining the state of failure and show signs of distress before the expected life span used for construction is reach, due to the lack of factors such as lack of maintenance culture etc. many of our road today serve as death trap and hang out for hoodlums going by the number of accident recorded daily on them as a result of bad paved road.

Pavement failure can be defined as the failure of the constructed layer of durable material of specified thickness, usually of concrete, asphalt or bituminous materials assigned to carry wheeled vehicles. Due to the number of load passing through a pavement structure, some deflection of the surface and underlying layers occur. The deflection can be as a result of the excess load, poor material usage, and poor road foundation resulting from the nature of the soil or groundwater rise in the area of high groundwater level. If layers are lacking in strength, repeated applications causes roughening and cracking that ultimately lead to failure of the pavement structure.

The construction of the Eliozu-New Airport road, which was constructed a while ago, sudden failure due to improper investigation of either the soil composition or traffic capacity situation in the said section of the road networking, lack of proper drainage to control the effect of rise in groundwater level. The pavement thickness of the road section as measure was about 3.87inches (98.3mm) and the width of the dual carriageway about 7.9m with no proper shoulder and drainage provided.

The effort of put in controlling the rate of failure and provision for annual increase of traffic capacity has been a thing of burden to the government of the River State in particular and the Federal government in general. By questioning and observation, failure of the said Eliozu-New Airport road as it problem from compounded presence of water coming out at a particular points on the road surface poor material and workmanship and pressure from increasing traffic capacities on the road pavement of which the government is making provision for overhead bridge which is currently in construction and it is found out that most at a point like Eliozu junction by ABC shuttle, the pavement bituminous material on the road have disappear.


The major objective of this investigation is to ascertain factors that likely lead to the failure of Eliozu-New Airport road in Obio/Akpor L.G.A. of River State in particular and Nigeria Highways in general and how it affect national stability and development. This project work stand at a point to unveil the very facts behind why most of the roads fail soon after construction.

The count carryout will broadly provide information on the actual traffic volume and the capacity of traffic and will help in used for possible traffic planning and design.

It shall lead in proper construction of highway and remedy that will possible give a lasting solution and reduction in road failures. The several test such as test on asphalt, test on soil will provided better facts to the cause of the failure of the case study.


The whole section of the road was visited (Reconnaissance) and failure pattern noted.
The project scope includes:

– Assessment of kind of failure and causes on the Eliozu-New Airport road.

– Soil samples collection and testing and analysis to determine the sub-grade, sub-base strength of the road foundation.

– Assessment of underground water level and its affect on the pavement.

– Assessment of traffic capacity intensity on the networking plan of the road and volume determination.

– Assessment of drainage condition and proper drainage provision.

– Assessment of the proportion and amount of bitumen and finer used in the Asphalt mixture used for the surface course.

– Classification of the soil according to ASSHATO classification system.

– Enumeration of possible pavement distresses that are found along a road section.


The location of which this investigation is been carryout is a road network located at Obio/Akpor L.G.A at the out script of Port Harcourt, River State. The road is from Eliozu junction to Airport road leading to Elele of which concentration is lay on the Eliozu junction where ABC shuttle is, at where over head bridge is undergoing construction currently to where the Eliozu-New airport road intersect with the airport road.


This research was carried out under the limits of the available material and resources. The work is centre on soil sample testing and classification, asphalt testing and traffic volume and effect of groundwater on road bases.

The following factors hinder the prompt attainment of this project work.

– Lack of laboratory facilities.

– Cost of the project work.

– Time proximities.

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