CIV3703 Transport Engineering
CIV3703 Transport Engineering Module 7 – Part 3 Road Construction and Maintenance
Dr. Andreas Nataatmadja
7.12 The Need for Road Maintenance Roads deteriorate due to effect of Climate, and Traffic.
The principle objectives in road maintenance are to maintain traffic safety and to protect the road asset.
7.13 Maintenance Management Fund available for maintenance never seems to be sufficient Productivity in road maintenance is heavily depends on Correct assessment Use of appropriate plants (technology) and personnel Maintenance technology is an ever changing area
7.13 Maintenance Management Routine Maintenance Cannot be predicted or planned in detail Assessed on accepted levels of service It includes; Pothole repairing Grading gravel or earth shoulders Controlling vegetation Washing, cleaning or renewing signs Repainting road and line markings Performed by permanent maintenance group, consist of 3~4 men equipped with a truck and hand tool. May require full traffic control.
Special Maintenance It can be predicted and planned, therefore subject to rigorous planning. Requires full traffic control. It includes: Asphalt overlaying Bitumen resealing Shoulder re-sheeting Special maintenance will usually be carried out by specialist gangs It also has routine components in it, which will be performed by the permanent maintenance group.
Restoration Repairing damage caused by events beyond the control of the road authority. It includes: Restoration of road and bridges after scouring by floods Removal of fallen trees after wind or lightning storms Replacement of road furniture after bushfires/accidents Performed by permanent maintenance gangs or patrols. May require full traffic control.
Maintenance Planning and Management Establish standards Assess condition of the road network Plan and budget Execute maintenance work Measure and record work done
Step 1. Establishing Standards Public expects certain defects to be rapidly repaired (e.g., potholes, damaged signs, accumulated rubbish/litter, loose gravel) The Standards help establish road defect severity levels: To justify maintenance or rehabilitation To maintain the public safety The standards provide: a means for assessing deficient road conditions a means for setting varying acceptable levels of deterioration based on road classification and traffic volume guidance in setting priorities.
Severity of Deficiencies The severity of deficiencies which can be tolerated is influenced by various factors such as road classification, climatic conditions, soil type, form of construction, and the volume and type of traffic using the road. It is therefore not practical to adopt one universal standard which applies to all road types and conditions.
Step 2. Assessing the Condition Generally done on regular basis Annual inspection to establish annual maintenance program Frequent inspection to establish routine maintenance Different road features need to be assessed under different operating conditions, e.g.: Night-time Reflectiveness of road sign, road lights Raining effectiveness of the drainage structure
Step 3. Planning and Budgeting Priorities, plans and costing for maintenance work
Step 4. Executing Maintenance Works Road authority, local councils, state road departments Recent shift: Public Private
Step 5. Measure and Recording Work Done Provides information for future works, planning and expenditure monitoring.
7.14 Maintenance of Road Drainage Systems Drainage system is the most important part of any road. Functions: Remove water from carriageway & formation Intercept surface water flowing towards the road formation Intercept ground water that would otherwise penetrate the subgrade
A general rule: it is good practice to minimise interfering with the natural flow of water (e.g. crossing river)
Scouring Flow of water should not be concentrated to avoid scouring
7.14.2 Bituminous and Concrete Pavements Crossfalls of 2 to 3 % Surface should be maintained in a waterproof condition with adequate drainage system Cracks and depressions should be repaired quickly
7.14.3 Gravel Surfaces Ponding of water should be avoided. Surfaces are not waterproof, therefore crossfalls is usually increased to 4 or 5% Keep whole surface in a smooth and self-draining condition by frequent grading
7.14.4 Unpaved Surfaces Crossfalls normal to centreline to speed up removal of surface water. Development of wheel ruts and deepening by succeeding vehicles tracking are common occurence.
7.14.5 Drainage Structures Table Drains Table drains require frequent maintenance silt & debris removal grading to restore the original shape
Batter Drains
Water from table drains must be discharged down the embankment batters Batter drains are generally lined with concrete, metal or some hard material Steep batter drains - check for scour
Catch Drains
Catch drain is to intercept surface water flowing towards the road cutting or formation embankment Usually open earth channels Check for obstructions, scour
Culverts
Passing the water from one side of the road to the other Failures have serious consequences Clearing, removal of channel growth, check scour and settlements
Subsoil Drains
It helps to lower the water table and drain trapped underground water To be effective it should be located more than 500 mm below the subgrade level Maintenance of subsoil drains: locate and check outlets if functioning Any growth or siltation at the outlet should be cleaned.
Construction of Subsoil Drains
Underground Drains and Pits (Urban area )
Pipes & conduits, generally parallel to road centreline Transverse pipes passing under the road formation Manholes located at the junctions permits inspection and clearing Frequent inspection and cleaning of the system is essential (functioning, check for silt & debris) Other tasks includes replacing or repairing damage structural elements of the system.
7.15 Maintenance of Earth and Gravel Roads Generally low traffic volumes – many kms of roads in Australia Maintenance needs a relatively low cost and little effort Earth roads may have to be imposed restriction on their use during adverse weather may have to be restricted to dry weather use
7.15 Maintenance of Earth and Gravel Roads Adequate maintenance is of great importance to the rural community Maintenance: Grading Scarifying and reshaping Gravel resheeting
7.15.2 Grading Important in the maintenance of earth and gravel roads Bring the material in from the side to maintain shape and free draining condition.
7.15.3 Scarifying and Shaping When the road has become worn to a state where the surface has hollows, potholes and corrugation, loosening and reshaping is recommended.
7.15.3 Scarifying and Shaping Success depends on the thickness of gravel remaining If the thickness of gravel < 75mm fresh gravel must be added increase it to a minimum thickness (say 100mm). If necessary water should be added to get adequate moisture for compaction
7.15.4 Gravel Resheeting Steps: Tyning of existing gravel To loosen the surface to permit movement by grader to restore the shape Spreading of new gravel Avoid segregation – Use spreader box, small heaps Compaction Commenced after full thickness of gravel has been spreaded and shaped Equipment requirements: Loader & Trucks, Graders, and Water cart & Rollers
7.16 Bituminous Surfaced Pavements Bituminous surface used to resist abrasion of traffic & prevent penetration of moisture Repair: must diagnose source of failure - surfacing, pavement, subgrade, moisture excavation of faulty material – for recycling? Backfill (max. 100 mm per layer), compaction, resurfacing. Partial- patching (< 100 mm) or deep-patching (> 100 mm): may use premix
7.16.3 Defects and Repair -1 Ravelled Surface loss of aggregate from plant mix cause: insufficient or aged binder, poor aggregate, excessively open graded mix repair: more binder, resurfacing (e.g., seal, slurry seal, enrichment seal, resurfacing with plant mix)
Defects and Repair - 2 Stripped Surface loss of aggregate from sprayed seal cause: design, construction, binder, age repair: enrichment seal, reseal
Reasons for Stripped Surface ageing and hardening of the binder cold or wet weather before, during, or soon after spraying wet or dusty aggregate to which the binder has not readily adhered insufficient binder for the size of aggregate used aggregate of a rock type to which the binder does not readily adhere insufficient cutter in the binder when spraying, preventing the binder from wetting the aggregate properly excess cutter in the binder when spraying, making the binder too soft to hold the aggregate under the action of traffic insufficient rolling and/or excessive brooming of the aggregate before allowing it to be traversed by fast traffic aggregate size incompatible with the aggregate size of the previous seal.
Defects and Repair - 3 Fatty or Slick (Bleeding, Flushed) Surfaces surplus binder on surface cause: too much binder, aggregate sinking or lost repair: binder removal, place more aggregate, resurfacing, burning-off
Reasons for Fatty or Slick Surface loss of cover aggregate from sprayed seals due to stripping excessive application of binder during surfacing operations or excess binder rising from the underlying surface, bad patches, etc. breakdown of aggregate poor spreading of cover aggregate in sprayed seals over-filled voids in plant mix graded cover aggregate with particles so small that they are covered by the binder or aggregate penetrating the pavement surface and sinking into the binder.
Defects and Repair - 4 Polished Aggregate Surface aggregate particles polished under traffic cause: age, poor aggregate repair: resurfacing with either plant mix, sprayed seal or slurry seal
Defects and Repair - 5 Shoving waviness transverse to direction of travel cause: horizontal shear force caused by traffic repair: repair with a stable mix; reconstruct
Defects and Repair - 6 Rutting Depressions along wheel tracks cause: asphalt deformation or, when accompanied with bulging, failure in the pavement structure or subgrade repair: as for shoving
Defects and Repair - 7 Cracks Surface may crack for variety of reasons, and often in the early stages Crack patterns help to identify the course of failure block crocodile crescent shaped diagonal longitudinal transverse Reflective meandering cracking
Identification, Causes and Treatment of Visual Distress Refer to Appendix A of
Defects and Repair – 7 Cracks Repair: Wide: clean and fill Fine: resurface If cracking caused by excessive deflection, the cause of the deflection MUST be eliminated first (may require complete reconstruction)
Defects and Repair - 8 Potholes moisture entry to pavement repair: vertical trim, removal of loose material, material reinstatement, resurfacing
Defects and Repair - 9 Edge Failures breaking of edge of bituminous surfacing Cause: narrow surfacing, worn shoulders, water repair: boxing, resurfacing, shoulder repair
Defects and Repair - 10 Large Depressions fill movement inadequate fill compaction repair: patch, reconstruction if necessary
7.17 Maintenance of Road Shoulders Shoulders are provided to: provide lateral support to the pavement carry surface water clear of the pavement to side or table drains keep the moisture content at equilibrium under the surfacing provide extra width for traffic to stop or stand, or for use in emergencies create a sense of open space and thus increase the effective use of traffic lanes.
7.17 Maintenance of Road Shoulders A shoulder should have A smooth running surface A minimum of loose materials Adequate slope for drainage Sufficient strength Flush with road surface Need regular maintenance Vary according to environmental, traffic, safety and other requirements If mowers are to be used, minimise the risk from flying objects
End of Module 7
Dr. Andreas Nataatmadja
7.12 The Need for Road Maintenance Roads deteriorate due to effect of Climate, and Traffic.
The principle objectives in road maintenance are to maintain traffic safety and to protect the road asset.
7.13 Maintenance Management Fund available for maintenance never seems to be sufficient Productivity in road maintenance is heavily depends on Correct assessment Use of appropriate plants (technology) and personnel Maintenance technology is an ever changing area
7.13 Maintenance Management Routine Maintenance Cannot be predicted or planned in detail Assessed on accepted levels of service It includes; Pothole repairing Grading gravel or earth shoulders Controlling vegetation Washing, cleaning or renewing signs Repainting road and line markings Performed by permanent maintenance group, consist of 3~4 men equipped with a truck and hand tool. May require full traffic control.
Special Maintenance It can be predicted and planned, therefore subject to rigorous planning. Requires full traffic control. It includes: Asphalt overlaying Bitumen resealing Shoulder re-sheeting Special maintenance will usually be carried out by specialist gangs It also has routine components in it, which will be performed by the permanent maintenance group.
Restoration Repairing damage caused by events beyond the control of the road authority. It includes: Restoration of road and bridges after scouring by floods Removal of fallen trees after wind or lightning storms Replacement of road furniture after bushfires/accidents Performed by permanent maintenance gangs or patrols. May require full traffic control.
Maintenance Planning and Management Establish standards Assess condition of the road network Plan and budget Execute maintenance work Measure and record work done
Step 1. Establishing Standards Public expects certain defects to be rapidly repaired (e.g., potholes, damaged signs, accumulated rubbish/litter, loose gravel) The Standards help establish road defect severity levels: To justify maintenance or rehabilitation To maintain the public safety The standards provide: a means for assessing deficient road conditions a means for setting varying acceptable levels of deterioration based on road classification and traffic volume guidance in setting priorities.
Severity of Deficiencies The severity of deficiencies which can be tolerated is influenced by various factors such as road classification, climatic conditions, soil type, form of construction, and the volume and type of traffic using the road. It is therefore not practical to adopt one universal standard which applies to all road types and conditions.
Step 2. Assessing the Condition Generally done on regular basis Annual inspection to establish annual maintenance program Frequent inspection to establish routine maintenance Different road features need to be assessed under different operating conditions, e.g.: Night-time Reflectiveness of road sign, road lights Raining effectiveness of the drainage structure
Step 3. Planning and Budgeting Priorities, plans and costing for maintenance work
Step 4. Executing Maintenance Works Road authority, local councils, state road departments Recent shift: Public Private
Step 5. Measure and Recording Work Done Provides information for future works, planning and expenditure monitoring.
7.14 Maintenance of Road Drainage Systems Drainage system is the most important part of any road. Functions: Remove water from carriageway & formation Intercept surface water flowing towards the road formation Intercept ground water that would otherwise penetrate the subgrade
A general rule: it is good practice to minimise interfering with the natural flow of water (e.g. crossing river)
Scouring Flow of water should not be concentrated to avoid scouring
7.14.2 Bituminous and Concrete Pavements Crossfalls of 2 to 3 % Surface should be maintained in a waterproof condition with adequate drainage system Cracks and depressions should be repaired quickly
7.14.3 Gravel Surfaces Ponding of water should be avoided. Surfaces are not waterproof, therefore crossfalls is usually increased to 4 or 5% Keep whole surface in a smooth and self-draining condition by frequent grading
7.14.4 Unpaved Surfaces Crossfalls normal to centreline to speed up removal of surface water. Development of wheel ruts and deepening by succeeding vehicles tracking are common occurence.
7.14.5 Drainage Structures Table Drains Table drains require frequent maintenance silt & debris removal grading to restore the original shape
Batter Drains
Water from table drains must be discharged down the embankment batters Batter drains are generally lined with concrete, metal or some hard material Steep batter drains - check for scour
Catch Drains
Catch drain is to intercept surface water flowing towards the road cutting or formation embankment Usually open earth channels Check for obstructions, scour
Culverts
Passing the water from one side of the road to the other Failures have serious consequences Clearing, removal of channel growth, check scour and settlements
Subsoil Drains
It helps to lower the water table and drain trapped underground water To be effective it should be located more than 500 mm below the subgrade level Maintenance of subsoil drains: locate and check outlets if functioning Any growth or siltation at the outlet should be cleaned.
Construction of Subsoil Drains
Underground Drains and Pits (Urban area )
Pipes & conduits, generally parallel to road centreline Transverse pipes passing under the road formation Manholes located at the junctions permits inspection and clearing Frequent inspection and cleaning of the system is essential (functioning, check for silt & debris) Other tasks includes replacing or repairing damage structural elements of the system.
7.15 Maintenance of Earth and Gravel Roads Generally low traffic volumes – many kms of roads in Australia Maintenance needs a relatively low cost and little effort Earth roads may have to be imposed restriction on their use during adverse weather may have to be restricted to dry weather use
7.15 Maintenance of Earth and Gravel Roads Adequate maintenance is of great importance to the rural community Maintenance: Grading Scarifying and reshaping Gravel resheeting
7.15.2 Grading Important in the maintenance of earth and gravel roads Bring the material in from the side to maintain shape and free draining condition.
7.15.3 Scarifying and Shaping When the road has become worn to a state where the surface has hollows, potholes and corrugation, loosening and reshaping is recommended.
7.15.3 Scarifying and Shaping Success depends on the thickness of gravel remaining If the thickness of gravel < 75mm fresh gravel must be added increase it to a minimum thickness (say 100mm). If necessary water should be added to get adequate moisture for compaction
7.15.4 Gravel Resheeting Steps: Tyning of existing gravel To loosen the surface to permit movement by grader to restore the shape Spreading of new gravel Avoid segregation – Use spreader box, small heaps Compaction Commenced after full thickness of gravel has been spreaded and shaped Equipment requirements: Loader & Trucks, Graders, and Water cart & Rollers
7.16 Bituminous Surfaced Pavements Bituminous surface used to resist abrasion of traffic & prevent penetration of moisture Repair: must diagnose source of failure - surfacing, pavement, subgrade, moisture excavation of faulty material – for recycling? Backfill (max. 100 mm per layer), compaction, resurfacing. Partial- patching (< 100 mm) or deep-patching (> 100 mm): may use premix
7.16.3 Defects and Repair -1 Ravelled Surface loss of aggregate from plant mix cause: insufficient or aged binder, poor aggregate, excessively open graded mix repair: more binder, resurfacing (e.g., seal, slurry seal, enrichment seal, resurfacing with plant mix)
Defects and Repair - 2 Stripped Surface loss of aggregate from sprayed seal cause: design, construction, binder, age repair: enrichment seal, reseal
Reasons for Stripped Surface ageing and hardening of the binder cold or wet weather before, during, or soon after spraying wet or dusty aggregate to which the binder has not readily adhered insufficient binder for the size of aggregate used aggregate of a rock type to which the binder does not readily adhere insufficient cutter in the binder when spraying, preventing the binder from wetting the aggregate properly excess cutter in the binder when spraying, making the binder too soft to hold the aggregate under the action of traffic insufficient rolling and/or excessive brooming of the aggregate before allowing it to be traversed by fast traffic aggregate size incompatible with the aggregate size of the previous seal.
Defects and Repair - 3 Fatty or Slick (Bleeding, Flushed) Surfaces surplus binder on surface cause: too much binder, aggregate sinking or lost repair: binder removal, place more aggregate, resurfacing, burning-off
Reasons for Fatty or Slick Surface loss of cover aggregate from sprayed seals due to stripping excessive application of binder during surfacing operations or excess binder rising from the underlying surface, bad patches, etc. breakdown of aggregate poor spreading of cover aggregate in sprayed seals over-filled voids in plant mix graded cover aggregate with particles so small that they are covered by the binder or aggregate penetrating the pavement surface and sinking into the binder.
Defects and Repair - 4 Polished Aggregate Surface aggregate particles polished under traffic cause: age, poor aggregate repair: resurfacing with either plant mix, sprayed seal or slurry seal
Defects and Repair - 5 Shoving waviness transverse to direction of travel cause: horizontal shear force caused by traffic repair: repair with a stable mix; reconstruct
Defects and Repair - 6 Rutting Depressions along wheel tracks cause: asphalt deformation or, when accompanied with bulging, failure in the pavement structure or subgrade repair: as for shoving
Defects and Repair - 7 Cracks Surface may crack for variety of reasons, and often in the early stages Crack patterns help to identify the course of failure block crocodile crescent shaped diagonal longitudinal transverse Reflective meandering cracking
Identification, Causes and Treatment of Visual Distress Refer to Appendix A of
Defects and Repair – 7 Cracks Repair: Wide: clean and fill Fine: resurface If cracking caused by excessive deflection, the cause of the deflection MUST be eliminated first (may require complete reconstruction)
Defects and Repair - 8 Potholes moisture entry to pavement repair: vertical trim, removal of loose material, material reinstatement, resurfacing
Defects and Repair - 9 Edge Failures breaking of edge of bituminous surfacing Cause: narrow surfacing, worn shoulders, water repair: boxing, resurfacing, shoulder repair
Defects and Repair - 10 Large Depressions fill movement inadequate fill compaction repair: patch, reconstruction if necessary
7.17 Maintenance of Road Shoulders Shoulders are provided to: provide lateral support to the pavement carry surface water clear of the pavement to side or table drains keep the moisture content at equilibrium under the surfacing provide extra width for traffic to stop or stand, or for use in emergencies create a sense of open space and thus increase the effective use of traffic lanes.
7.17 Maintenance of Road Shoulders A shoulder should have A smooth running surface A minimum of loose materials Adequate slope for drainage Sufficient strength Flush with road surface Need regular maintenance Vary according to environmental, traffic, safety and other requirements If mowers are to be used, minimise the risk from flying objects
End of Module 7
