Investigation on the Causes of Pavement Failure
One of the major problems facing the country is pavement failure. It is the concern of the Institute of Management and Technology (IMT) authorities to carryout a case study of pavement failure along Hillview off ESBS Road Enugu.
The investigation show that the pavement failed both structural and functionally taking into consideration.
The possible cause cure:-
(a) Poor sub-grade & sub-base
(b) Lack of maintenance culture
(c) Poor drainage system
(d) Poor workmanship
TABLE OF CONTENTS
1.3 Pavement Definition
1.4 Types of Road pavement
1.5 Advantages and Disadvantages of Flexible & Rigid Pavement
1.6 Functions and Pants Pavement
1.7 Sub – Grade
1.8 Sub – Base
1.10 Wearing Course
1.11 Pavement Failure
1.16 Aligator Cracking
1.17 Longitudinal Cracking
CAUSES OF PAVEMENT FAILURES ALONG HILLVIEW OFF ESBS ROAD
2.1 Traffic Intensity
2.2 Improper Drainage System
2.3 Unskilled Manpower
2.4 Improper Compaction
2.5 Much Clay
Effects of Pavement Failure
2.7 Maintenance Cost
3.1 Importance of Soil Test In Pavement Design
3.2 Mechanical Analysis Test
3.3 Standard Compaction Test
3.4 Carliform Bearing Ration
3.5 Alterberg Limit Test
3.6 Liquid Limit & Plastic Limit
Description Method and Result of Test
4.1 Compaction Test
4.2 Carliform Bearing Ratio
4.3 Mechanical Analysis Test
4.4 Alterberg Limit Test
5.1 Improvement on the Pavement Failure
5.3 General Conclusion
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.
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.
A known depression in the pavement parallel to the side is serially 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.
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.
A braking of the visible loose particles or pieces of aggregates considered slightly when only a few piece of aggregate are dislodged from the pavement and are loosely silting above the street surface. Moderate when enough piece of loose aggregate are present to cover wide area of the surface and survey when the loose aggregate is so prevalent that they make the surface rough.
This occurs when asphalt covers the aggregate on the pavement. It is slight the covering is noticeable moderate when long areas are covered and serves when asphalt is totally covering the aggregate.
1.21 ALIGATOR CRACKING
This occurs when crack is like skin of alligator. The crack are said to be slight when barely visible, moderate when the cracks are more than 6.25mm wide in some place but side and cracks not fully separated. They are usually associated with a granular untreated base that has failed with a resident sub grade.
1.22 POT HOLE
These are bower or cup shaped holl of various sizes in the pavement resulting from localized disintegration. They are usually caused by weakness in the pavement resulting from too little asphalt or too tin asphalt or too many fine too few fire or poor drainage.
These are normally caused by too little compaction or too many fines in the surface course or settlement like cracks distortion take a number of different forms channeling, corruption, shoring, depression and uphaueaved pavement distortion is any change in the pavement surface from its original shape.
Localized upward displacement that is due to swelling of the sub-grade on some portion of the pavement. It is commonly cause by ice penetration in the sub-grade it may also be caused by swelling effects or moisture on exposed soils.
1.25 SPALLING EDGES
This is a result of the vehicle travelling along the edge of the carriage way or to the continual absorption of surface water. These are deep potholes shallow pot holes which constitutes a very dangerous treat to both life and property including passing traffic on the road. It is normally experienced at the edge of a flexible carriage way where a separate channel course.
1.26 SUMMARY OF PAVEMENT FAILURE
The pavement fails because the sub-grade, base course wearing surface course has failed. Sub-grade failure results when the applied load on soil expells all then water and air pressure in pores of the sub grade combined with the force produce by the applied force such as plastic deformation si progressively under repetition of load and is the major course of road failure. Insufficient stability of soil which may be as a result of excessive moisture, improper compaction of soil itself may be another coarse of pavement failure.
(a) Poor materials used in the base course
(b) Loss of binding or inter locking properties of the materials.
(c) Loose of material from base course
(d) Loose of factual support to the base course
(e) Poor drainage both for surface and sub surface improper and inadequate compaction
(f) Poor proportions of the materials
1.27 WEARING COURSE MAY FAIL DUE TO
(a) Improper quality of binding in the mix
(b) Inferior quality of binding used
(c) More than required quality of binder
(d) Inadequate of binding used
(e) Volatilization and oxidation of binder which make bitumenous stalling brittle and course cracking of the surface.
1.28 RECONNAISSANCE SURVEY
A visual survey was carried out to investigate the following
(a) The topography and feature along the road
(b) The nature and types of pavement materials
(c) The drainage pattern in relation to expected run off
(d) The pavement profile, sup— elevation, depth and construction material
(e) The pavement is of flexible type, made of asphalt with crush stone.]
(f) Poor drainage system – the installed drainage system is not available and so causes water to percolate around the pavement.
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