REASONS OF ROAD FAILUREA report of the subject Technical Writing and Communication Skills

Submitted to: Mohammad Irfan Kakar

Lecturer Department Of Civil Engineering

BUITEMS, PAKISTAN.

Submitted By

Shah Zaman…………………………………………..8515 Alamgir Khan…………………………………………8974 Arif Khan Kakar……………………………………..8597 Muhammad Khan………………………………….8769 Kaleemullah………………………………………….9497

Acknowledgment

First of all we all would like to Thank Mr. Irfan Kakar who has given a best opportunity to us to work on the given interesting topics regarded our profession. And I am thankful of my group member who help me to make a such interesting technical report.

Table contents

Abstracts……………………………………………..1

Introduction…………………………………………1

Reason of Road failure………………………..3

Fatigue failure……………………………………..6

Bleeding………………………………………………14

Depression………………………………………….22

Failure due to compaction………………….45

Failures due to camber………………………45

References

AbstractIn this report we have explained the reasons of road failures; especially we have failures due to fatigue, bleeding, cambers and improper compaction. If we didn’t act upon safety codes then we may face this problem.

Introduction

Roads are the basic needs of communications and it is most commonly used in our daily life for the travelling, transport and carriage. Due to its importance we should pay special attention to its each step while making a road. If we do not follow the codes and safety measures given according to specification then we may face many problems about road failures. Generally the road failures occur due to fatigue (alligator) cracking bleeding block cracking depression longitudinal cracking Patching Polished aggregate rutting slippage cracking stripping transverse (thermal) cracking .

Reasons: 1- Fatigue (Alligator) Cracking

Description: Series of interconnected cracks caused by fatigue failure of the HMA surface (or stabilized base) under repeated traffic loading. In thin pavements, cracking initiates at the bottom of the HMA (hot mix asphalt) layer. This is commonly referred to as "bottom-up" or "classical" fatigue cracking. The reasons of fatigue are

Decrease in pavement load supporting characteristics

Loss of base, sub base or subgrade support (e.g., poor drainage or spring thaw resulting in a less stiff base).

Increase in loading (e.g., more or heavier loads than anticipated in design)

Inadequate structural design

Poor construction (e.g., inadequate compaction)

BleedingThis can be caused by one or a combination of the following:

Excessive asphalt binder in the HMA (either due to mix design or manufacturing)

Excessive application of asphalt binder during BST (bituminous surface treatment) application (as in the above figures)

Low HMA air voids content.

Block Cracking►Description: Interconnected cracks that divide the pavement up

into rectangular pieces. Block cracking normally occurs over a large portion of pavement area but sometimes will occur only in non-traffic areas.

Depression►Description: Localized pavement surface areas with slightly lower

elevations than the surrounding pavement. Depressions are very noticeable after a rain when they fill with water.

►Problem: Roughness, depressions filled with substantial water can cause vehicle hydroplaning

►Possible Causes: Frost heave or subgrade settlement resulting from inadequate compaction during construction.

Longitudinal Cracking►Description: Cracks parallel to the pavement's centerline or

laydown direction. Usually a type of fatigue cracking.

►Problem: Allows moisture infiltration, roughness, indicates possible onset of alligator cracking and structural failure.

►Possible Causes:

►Poor joint construction or location. Joints are generally the least dense areas of a pavement. Therefore, they should be constructed outside of the wheelpath so that they are only infrequently loaded.

Patching►Description: An area of pavement that has been replaced with

new material to repair the existing pavement. A patch is considered a defect no matter how well it performs.

►Problem: Roughness

►Possible Causes:

►Previous localized pavement deterioration that has been removed and patched

Slippage►Description: Crescent or half-moon shaped cracks generally

having two ends pointed into the direction of traffic.

►Problem: Allows moisture infiltration, roughness

► Possible Causes: Braking or turning wheels cause the pavement surface to slide and deform. The resulting sliding and deformation is caused by a low-strength surface mix or poor bonding between the surface HMA layer and the next underlying layer in the pavement structure.

Transverse (Thermal) Cracking►Description: Cracks perpendicular to the pavement's centerline or

laydown direction. Usually a type of thermal cracking.

►Problem: Allows moisture infiltration, roughness

►Possible Causes: Several including:

►Shrinkage of the HMA surface due to low temperatures or asphalt binder hardening

►Reflective crack caused by cracks beneath the surface HMA layer

► top-down cracking

Failure due to compactionCompaction is the process that bring about an increase in a soil density or unit weight a accompanied by decrease in air volume. If we not compact the soil of the road there will be air voids in soil and will case failure

Failure of a road due to camber►The camber is any curve on a surface, and in this case refers to

upward curve from the edge. You may sometimes notice that the road isn’t exactly flat. The reason for that is because most roads have a camber to them that helps water drain off of them rather than pooling up in the center of the road. If we not provide camber there will be no proper drainage of water and water will go inside of a road and failure will occur

God helps those who help them selves

The End