CHAPTER ONE

1.1             INTRODUCTION

The site under investigation is Hillview of ESBS Road Enugu.

Along the site failures are observed especially depress on pavement and lost of pavement totally which are caused by excessive moisture in the sub – grade.

The aim of the investigation is to know  the extent of the failure on the flexible pavement and the nature of the failure.

The aim is also to give recommendation on how to improve the pavement which has occurred at the site under investigation.

1.2             LITERATURE REVIEW

The uses and application of modern technologies and new concepts have been deviced to tackle problem of pavement failure by many organized bodies.

1.3             DEFINITION OF PAVEMENT

a pavement can be defined as the hard crust of the road structure placed above the soil formation or sub-grade.

1.4             FUNCTIONS

The function of pavement is to transmit acceptable pressure to the bearing subgrade through sub base soil which must be less than the bearing capacity of the soil sub-grade.

1.5             TYPES OF ROAD PAVEMENT

There are two main types of pavement

(i)               Flexible Pavement

(ii)             Rigid Pavement

1.6             FLEXIBLE PAVEMENT

This consist of various lagers of high way building materials compacted so as to be void free and finished with elastic surface such as bitumen as asphalt maintain intimate constant and distributes inter lock, particle reaction and cohesiol per stability.

1.7             ADVANTAGES OF FLEXIBLE PAVEMENT

If good services are to be received from bituminous pavement it must be for its full life, retain the following qualities.

(i)               Smooth riding or in skid surface

(ii)             Tight, impermeable surface or porous surface

(iii)          No cracking or fatigue failure

(iv)           Resistance of weather

(v)             Resistance of moisture

1.8             DISADVANTAGE OF FLEXIBLE PAVEMENT

If not properly constructed --- will be

(i)               Poor weather resistance

(ii)             Presence of cracking

(iii)          High cost is incurred during construction

(iv)           Fatigue failure will occur

1.9             RIGID PAVEMENT

This type of pavement is made up of reinforcement or non – reinforcement concrete slab. It consist of two layers the cement slab and the snobs of granular material or stabilized soil.

These two large are sprees I n separate construction operation.

1.10         ADVANTAGE OF RIGID PAVEMENT

This types of pavement has long life, when properly design constructed.

It has low maintenance cost

The reinforcement made it not flexible

1.11         DISADVANTAGE OF RIGID PAVEMENT

(i)               Trans cracking of concrete paving slab under combined flexural and direct tensile stress is inevitable.

(ii)             Longitudinal crack slab more than one lone wide is also inevitable 

1.12         FUNCTION OF PARTS OF THE PAVEMENT STRUCTURES

SUB-GRADE:     This bears the load of pavement and traffic load in other to reduce the effective thickness, the bearing capacity is reduced by

(a)     Proper Compaction         (b)     Stabilization

(c)              Proper drainage 

1.13         THE SUB – BASE

This is introduced due to poor bearing capacity of the sub grade soil or high traffic density. It is made to improve earths its function is to transmits the traffic load from the road and spreading as jet over a large area of the sub grade formation level.

1.14         ROAD BASE

The function of the base is bearing the late load from the traffic and long heed from the over wearing surface and spreading it uniformly over a large area of the sub grade or sub-base.

1.15        SURFACING (WEARING COURSE)

The weary course is to spread the wheel load to the road base against surface water. The presence of bitumen improves the water proofing property. It also provide skid resistance.

1.16        PAVEMENT FAILURE

Pavement is bound to fail for many reasons not ably localized depression or settlement, but the most but the most common is lack of maintenance. From the day one pavement is exposed to traffic, the pavement is subjected to destructive forces. Temptation change settlement, precipitation and run – off and other natural phenomenous that stress the pavement structure increase addition of the load of traffic on the pavement increases the rate of failure. The serviceability or rider quality of a new pavement declines shallowly at first but as years pass rider quality begins to deteriorate mush more rapidly if maintenance is neglected and the situation is been worsen. The cost of rehabilitation must surly increase visual inspection can be used to determine pavement condition and degree of failure.

1.17         RUTTING

A known depression in the pavement parallel to the side is sevialy slight when the depression measures less than ½ + 1 inch deep, but not deep enough to pavement steering usually water accommodate in the depression,  promoting pavement failure. This depression can also be caused by traffic loading more than the bearing capacity of the pavement or by poor construction method.

1.18         CORRUGATION

The corrugation or coach boarding is a form of plastic movement.  Ripples and visible in the pavement perpendicular to this direction of traffic. The condition is slightly with barely visible sever when the ripples are so prevalent that they require the diver to reduce speed.

1.19        REVEALING

A braking of the visible loose particles or pieces of aggregates considered slightly when only a few piece of aggregate are dis

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