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Thesis presentation
1. S
INVESTIGATION INTO THE
FAILURES OF PAVEMENTS IN
FLOOD PRONE ZONES
By Kyran Tanuvasa
Student number:08305374
QUT (Queensland University of Technology)
2. S
Learning Outcomes
• Flood Zones (Brisbane)
• Types of Pavements
• Engineering Pavement Failures
• Solutions
Queensland’s road network (specifically Brisbane’s flood prone areas) has become a major issue over the past 15 years with many pavement designs failing under flood conditions .
The Department of Transport and Main Roads (DTMR) is the governing body for the Queensland road network, which controls approximately 35,000 km of road.
They plan, manage and deliver Queensland's integrated transport environment to achieve sustainable transport solutions for road, rail, air and sea (Queensland (Department of Transport and Main Roads), 2016). These roads consist of the main highways and other major connecting roads throughout the state.
Councils are deemed to control the less populated roads in its catchment. Depending on the significance, classification and Annual average daily traffic (AADT) of each road will determine if it is governed by DTMR or BCC.
The statistics say that 96,063 potholes have been filed, 12,150 m2 of new bikeways, 62,924 m2 of maintenance work to footpaths as well as 567,000 m2 of roads resurfaced.
In recent times flooding in Brisbane city has been a hot topic, especially after the 2011 floods that claimed the lives of 9 people and cost the government a total of 29.87 billion dollars Pavements that fail before the designed life span are a common occurrence within Brisbane’s road network, especially in flood prone zones. Each year it is costing taxpayers billions of dollars to keep the roads ‘roadworthy’.
Brisbane, the capital city in Queensland is also known as the river city. The reason being, the Brisbane River protrudes straight through the middle of the CBD and other surrounding suburbs.
After the 2011 floods, BCC issued the following suburbs as high risk flooding suburbs
Rocklea
Albion
Milton
Auchenflower
Norman Park
Pinkenba
Oxley
New Farm
Kangaroo Point
Bulimba & Sherwood
As demonstrated that the majority of these areas share its borders with the Brisbane River. Therefore they fell victim to the rising Brisbane river flood levels.
The surface that is subjected to loads from traffic vehicles travelling on it as well as pedestrians and other users, is known as a pavement. Pavements are durable and should provide friction for vehicles, which in turn will also provide comfort to the driver by dispersing the load applied to the pavement surface from the travelling vehicle down into the natural soil.
the two main pavement types are – flexible and rigid
For a pavement to be considered a flexible pavement it must usually be constructed in layers made up of granular material, which is then covered with one or more waterproof surface layers.
As the name suggests, under the load of a vehicle the pavement will flex
Rigid pavements are harder than flexible pavements and this is due to the surface course of rigid pavements. Unlike flexible pavements, rigid pavements can be constructed over weaker unsuitable layers due to the rigidity.
the 5 most common pavement failures found in Queensland are
Potholes are small, bowl-shaped depressions within the pavement surface that penetrate all the way through to the base course.
potholes are an indication of structural surface failure.
caused due to a lack of pavement strength or a problem with surfacing, such as inadequate thickness
Water that infiltrates the pavement causes the base and/or subgrade to become wet and unstable
eeding as the film of asphalt binder that appears on a road surface.
Bleeding can reduce skid resistance/ friction on the road, especially during wet conditions.
Bleeding is caused from inadequate seal coat, asphalt mixes, prime or bond coat applied inaccurately.
A rut is a permanent deformation (indentations) of the pavement in the wheel paths, which can lead to cracking and further deterioration
Rutting can be caused by stopping & standing traffic, heavy trucks, slow traffic, temperature susceptible asphalt, poor aggregate, poor construction, low air voids, too many fines, incorrect design thickness and settlement in lower layers, moisture damage and lack of compaction.
Cracking can be categorized into 4 different categories. They are:
Alligator Cracking
Reflection Cracking
Transverse Cracking
Longitudinal Cracking
No mater the initial cause or failure, each type becomes far more apparent and deteriorates rapidly when moisture/ water is able to infiltrate the pavement surface.
It has been found that an inadequate design or materials being used caused many problems.
Many road repair workers with extensive industry experience on a variety of TMR and BCC projects agree that a great deal of repairs might have been avoided if quality materials or construction methods were used during the construction stage.
Materials such as clay, which have an expansive nature when exposed to moisture, should never be used within roads. However it is not uncommon to still find hints of clay still being used in close proximity to pavement failures.
Recommendations have been made to decrease it to 6-month periods. This will allow road-works teams to identify current and potential issues before they progress in to major pavement failures.
Alternative drainage implementations will not stop all the featured pavement failures but they will definitely help slow the deterioration process. The inclusion of subsoil drains, culverts, steeper runoff slopes and larger capacity of storm water drains will ensure that flooding/ pooling on the road will be eliminated.
