Pavement Design Guidelines Rev A - City of Warrnambool · PDF fileinvestigations, structural design, pavement composition, acceptable materials and construction practices to be adopted

ACN: 099 065 380 Address: 103 Carrington Road, Box Hill 3128 Tel: (03) 9898 2230 Fax: (03) 9898 2606 Mobile 0402 319 652 E-mail: [email protected]

Pavement Design Guidelines

Rev A

R W Stamp & Associates Pty Ltd Traffic and Civil Engineers

Phone (03) 9898 2230

Fax (03) 9898 2606

Document History Issue

Revision

Issued to Copies

Date Approved

1 1 Warrnambool City Council 1 21/8/07 R Stamp Rev A Warrnambool City Council 1 11/10/0

7 R Stamp

mailto:[email protected]

7R0254:R01RWSWC.DOC Rev A R W Stamp & Associates Pty Ltd

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Pavement Design Guidelines ................................................................... i

Rev A ........................................................................................................... i

1. INTRODUCTION ....................................................................................................... 1 1.1 GENERAL .......................................................................................................... 1 1.2 SCOPE OF THIS GUIDE ......................................................................................... 1

2. GEOTECHNICAL INVESTIGATIONS ......................................................................... 2 2.1 GENERAL .......................................................................................................... 2 2.2 SUBGRADE TESTING ........................................................................................... 2 2.3 DETERMINATION OF SUBGRADE STRENGTH............................................................. 3

2.3.1 Residential Subdivisions ............................................................................ 3 2.3.2 Industrial Subdivisions ............................................................................... 3 2.3.3 Highly Reactive, High Plasticity Subgrades ................................................ 3

3. DESIGN TRAFFIC LOADING..................................................................................... 5 3.1 RESIDENTIAL STREETS ........................................................................................ 5

3.1.1 Road Classification..................................................................................... 5 3.1.2 Calculation of Design Traffic Loading......................................................... 5

3.2 RURAL RESIDENTIAL ROADS................................................................................. 6 3.2.1 Road Classification..................................................................................... 6 3.2.2 Calculation of Design Traffic Loading......................................................... 7

3.3 INDUSTRIAL SUBDIVISION ROADS .......................................................................... 8 3.3.1 Road Geometry ........................................................................................... 8 3.3.2 Calculation of Design Traffic Loading......................................................... 8

3.4 DESIGN TRAFFIC FOR RIGID PAVEMENTS ................................................................ 9 4. PAVEMENT DESIGN............................................................................................... 10

4.1 PAVEMENT DESIGN LIFE .................................................................................... 10 4.2 DESIGN RELIABILITY OF PAVEMENTS.................................................................... 10

4.2.1 Urban Residential Pavements ................................................................... 10 4.2.2 Rural Residential Pavements .................................................................... 10 4.2.3 Industrial Subdivision Pavements ............................................................ 10

4.3 FLEXIBLE PAVEMENT THICKNESS DESIGN ............................................................. 10 4.3.1 Non Expansive Subgrades........................................................................ 10 4.3.2 Highly Reactive High Plasticity Subgrades ............................................... 11

4.4 PAVEMENT COMPOSITION .................................................................................. 12 4.4.1 Urban Residential Streets ......................................................................... 12 4.4.2 Rural Residential Streets .......................................................................... 14 4.4.3 Industrial Subdivisions ............................................................................. 15 4.4.4 Highly Reactive High Plasticity Subgrade................................................. 15

4.5 SUBGRADE IMPROVEMENT ................................................................................. 16 4.6 RIGID PAVEMENT DESIGN .................................................................................. 17 4.7 INTERSECTIONS ................................................................................................ 17 4.8 ROUNDABOUTS ................................................................................................ 17

5. PAVEMENT MATERIALS ........................................................................................ 18 5.1 ASPHALT SURFACING ........................................................................................ 18 5.2 BITUMINOUS PRIME ........................................................................................... 19 5.3 GRANULAR PAVEMENT MATERIALS ...................................................................... 19 5.4 SUBBASE MATERIALS ........................................................................................ 19

6. SUBSURFACE DRAINAGE ..................................................................................... 21 6.1 GENERAL ........................................................................................................ 21 6.2 TYPES OF SUBSURFACE DRAINS ......................................................................... 21

6.2.1 Longitudinal Pavement Drains.................................................................. 21


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6.2.2 Transverse Pavement Drains .................................................................... 21 6.2.3 Rural Roads .............................................................................................. 21

6.3 LOCATION OF SUBSURFACE DRAINS .................................................................... 21 6.4 TYPE OF SUBSURFACE DRAINS ........................................................................... 22


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1. Introduction

1.1 General The Warrnambool City Council has been experiencing a significant growth in the demand for new residential developments within the municipality. In order to expediate approval of new developments, the Council is revising the Design Guidelines for Subdivisional Developments. As part of this work, Pavement Design Guidelines have been prepared to standardise the pavement type and thickness appropriate for use in new residential subdivisions. The objective of the Pavement Design Guidelines is to ensure uniformity in the approach to the design and construction of pavements, and to ensure that acceptable minimum standards necessary to achieve superior long term performance and to minimise subsequent maintenance requirements are met. The municipality covers a range of naturally occurring subgrade materials including highly reactive, high plasticity clays in some areas. Treatment of these highly reactive subgrade materials requires special design and construction techniques to minimise environmental cracking of the pavement. The Design Guidelines will minimise any confusion over the standards of pavement investigations, structural design, pavement composition, acceptable materials and construction practices to be adopted within the City of Warrnambool

1.2 Scope of this Guide The scope of the Pavement Design Guidelines covers the design and construction of pavements for residential and industrial subdivisions within the Warrnambool City Council. The design of the pavements will be carried out by qualified engineering consultants in accordance with this Guide and the principles, practices and procedures detailed in the following design references. Austroads (2004) ‘Guide to the Structural Design of Road Pavements’. APRG Report No 21 (1998) ‘A Guide to the Design of New Pavements for Light

Traffic.’ VicRoads (2005) RC 500.22 ‘Code of Practice for Selection and Design of

Pavements and Surfacing.’ VicRoads (1982) Technical Bulletin No 32 ‘ Drainage of Subsurface Water from

Roads’. Pavements should be designed in accordance with all the relevant requirements of the above references, subject to the limitations and additional qualifications as specified in this Design Guide.


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2. Geotechnical Investigations

2.1 General The Consultant shall arrange a detailed geotechnical investigation of the naturally occurring material along the alignment of the roads. The extent of any areas of filling should be determined and the strength of the underlying material determined. The geotechnical testing, including both field and laboratory testing shall be undertaken in accordance with all relevant Australian Standards and the following references. APRG Report No 21 (1998) ‘A Guide to the Design of New Pavements for Light

Traffic.’ VicRoads Technical Bulletin No 40. (1995) ‘Pavement Investigation Guide to

Field Inspection and Testing.’ VicRoads Manual Codes of Practice

2.2 Subgrade Testing The objective of the subgrade testing is to determine the support the subgrade will provide to the pavement over the design life. The support will be highly dependent on the material type, its moisture content and the degree of compaction. The following approach to the testing of the subgrade should be adopted for all subdivisions in the Warrnambool City Council. Excavation of test holes along the alignment of the roads at a spacing of between

100 to 150 metres for urban residential and industrial areas and up to 300 metres spacing on rural residential areas. A minimum of three test holes on any one project.

At least two test sites should be located along the alignment of the collector and

distributor roads where a regular bus route will operate in the residential subdivision.

At least two test sites should be located on all roads in the industrial subdivisions. The test holes should be excavated to a minimum depth of at least one metre

and should extend at least 500 mm below the proposed subgrade level. Dynamic cone penetrometer testing and excavation of undisturbed samples for

laboratory testing should be obtained from each test site. Moisture content testing of the material at each site should be carried out.

Grading and Atterberg testing (Liquid Limit, Plastic Limit, Linear Shrinkage and

Plasticity Index) should be carried out on the sampled material. Laboratory Soaked CBR tests should be carried out on the sampled material.

The subgrade material should be compacted at optimum moisture content to a


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density of 95% of maximum density using Standard compactive effort. The samples should be soaked for four days prior to testing.

Any filling placed on the naturally occurring material which extends to at least 500

mm below the proposed subgrade level shall be considered as the subgrade. The same testing regime detailed above shall apply to the filled material. Where the proposed subgrade level will be below the level of the filled material, the subgrade testing should be carried out on the naturally occurring material.

2.3 Determination of Subgrade Strength The following approach, which is based on Section 13.5.2 of the APRG Report No 21, shall be used to determine the subgrade strength. .

2.3.1 Residential Subdivisions The proposed subdivision should be classified into homogeneous sections in accordance with the proposed traffic loading, subgrade type, topography and drainage. In most cases, the access streets would be grouped into a homogeneous section unless there was a significant difference in the subgrade and drainage conditions. The Design CBR of the subgrade would be the mean value of the Laboratory Soaked CBR values. The collector and distributor roads would be treated as a homogeneous group. The Design CBR would be the mean of the Laboratory Soaked CBR values on these roads. If there was a significant difference between the values, the Optimum Moisture Content and the Atterberg Limit results should be checked to determine the reason. If the results of the testing appeared to be valid, the lowest value of the Laboratory Soaked CBR should be adopted.

2.3.2 Industrial Subdivisions The Design CBR would be the mean of the Laboratory Soaked CBR values on the roads. If there was a significant difference between the values, the Optimum Moisture Content and the Atterberg Limit results should be checked to determine the reason. If the results of the testing appeared to be valid, the lowest value of the Laboratory Soaked CBR should be adopted.

2.3.3 Highly Reactive, High Plasticity Subgrades There are sections of the Warrnambool City Council which have highly reactive, high plasticity clay subgrades. The determination of the Design CBR of the subgrade should incorporate the method detailed above. However, the subgrade design CBR assigned to highly reactive, high plasticity clay subgrades shall not exceed 4 %. Highly reactive materials exhibit significant volume changes with increases in moisture content leading to loss of pavement shape and longitudinal cracking in the outer edges of the pavement. These materials have a potential swell greater than 2.5 % and pavements constructed in these areas should incorporate a capping layer to minimise any moisture content changes in the subgrade.


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The classification of Expansive Soils is detailed in Table 5.2 of the Austroads ‘Guide to the Structural Design of Road Pavements.’ and reproduced below. Table 2.1 Guide to the Classification of Expansive Soils (Source: Austroads Guide to the Structural Design of Road Pavements) Expansive Nature

Liquid Limit (%)

Plasticity Index

PI x % < 0.425 mm

Potential Swell

Very High > 70 > 45 > 3200 > 5.0 High > 70 > 45 2200 – 3200 2.5 – 5.0 Moderate 50 – 70 25 – 45 1200 – 2200 0.5 – 2.5 Low < 50 < 25 < 1200 < 0.5


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3. Design Traffic Loading The design traffic loading for the roads detailed in this Design Guide are based on the following information.

3.1 Residential Streets

3.1.1 Road Classification The traffic loading for each street in the residential developments is based on the road classifications detailed in Clause 56 the Warrnambool City Council Planning Scheme. The classification of the residential streets is detailed as follows: Access Lane – A side or rear lane providing access to parking on lots with

another street frontage serving less than 10 dwellings and less than 300 vehicles per day.

Access Place – A minor street providing local residential access for up to 30

dwellings and less than 300 vehicles per day with shared pedestrian and traffic movements but with priority for pedestrians.

Access Street – Level 1 – A street providing for local residential access up to

100 dwellings with less than 1000 vehicles per day with shared pedestrian, bicycle and traffic movements.

Access Street – Level 2 – A street providing for local residential access up to

200 dwellings with traffic volumes between 1000 and 2000 vehicles per day with shared pedestrian, bicycle and traffic movements.

Collector Street – Level 1 – A street connecting access places and access

streets through and between neighbourhoods serving up to 3000 vehicles per day.

Collector Street – Level 2 – A street connecting the internal road system of a

residential development to the arterial road network serving up to 6000 vehicles per day.

Arterial Road – Non residential street providing for the through traffic to bypass

the residential areas. Road is typically a divided road with restricted access points serving greater than 7000 vehicles per day.

The Access Street, Collector and Arterial Roads may form part of a bus route.

3.1.2 Calculation of Design Traffic Loading The calculation of the Design Traffic Loading (DTL) for residential streets should take into account an assessment of the following factors. Design period which shall be at least 25 years. Existing traffic volumes using the road at the opening of the subdivision.


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Proportion of commercial vehicles using the road including an allowance for buses, construction traffic, delivery vehicles and service vehicles. The traffic loading in ESA’s generated by construction traffic shall not be less than 25 times the number of dwellings.

Predicted annual growth rate in commercial vehicles. The annual growth rate is

omitted for residential subdivisions where there is no externally generated through traffic.

Road geometry characteristics including pavement width, lane distribution on

multi lane roads and vehicle load factors. Typical road characteristics and traffic loadings for each of the road classifications are detailed in Table 3.1. Table 3.1 Typical Traffic Loadings on Residential Roads Street Type

Bus Route

Growth Rate

Daily Traffic (vpd)

% CV Load Factor (ESA’s / CV)

Design Traffic Loading (ESA’s)

Access Lane

No Nil 100 3 % 0.2 7.4 x 103

Access Place

No Nil 300 3 % 0.2 1.1 x 104

Access Street Level 1

No 1 % 1,000 4 % 0.3 6.6 x 104


Yes 1 % 2,000 6 % 0.3 3.0 x 105

Collector Road Level 1

No 2 % 3,000 5 % 0.4 3.6 x 105


Yes 2 % 6,000 7 % 0.6 1.7 x 106

Arterial Road

Yes 3 % 10,000 10 % 0.8 5.2 x 106

3.2 Rural Residential Roads

3.2.1 Road Classification The following classification of rural residential roads should be used in the design of the pavements. Rural Residential Access Court - Road providing for local residential access to

up to five properties with shared pedestrian, bicycle and traffic movements. The daily traffic volumes shall be less than 50 vehicles per day with vehicle speeds less than 80 km/h. The pavement shall provide for two way traffic on a 5.5 metre wide seal.

Rural Residential Access Road – Road providing for residential access to up to

six properties and connected to several rural residential access courts. The daily traffic volume shall be up to 300 vehicles per day with vehicle speeds up to 100 km/h. The pavement shall provide for two way traffic on a six metre wide seal.


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Rural Residential Road – Local through access road with a daily traffic volume

over 300 vehicles per day with vehicle speeds up to 100 km/h. The pavement shall provide for two way traffic on a seven metre wide seal.

Rural Collector Road – A road connecting rural residential access roads and

rural residential roads serving with daily traffic volumes over 300 vehicles per day. The pavement shall provide for two way traffic on a seven metre wide seal.

3.2.2 Calculation of Design Traffic Loading The calculation of the Design Traffic Loading (DTL) for rural residential streets should adopt a similar approach to the urban residential areas. An assessment of the following factors should be carried out. Design period which shall be at least 25 years. Existing traffic volumes using the road at the opening of the subdivision. Proportion of commercial vehicles using the road including an allowance for

buses, construction traffic, delivery vehicles and service vehicles. The traffic loading in ESA’s generated by construction traffic shall not be less than 25 times the number of dwellings.

Predicted annual growth rate in commercial vehicles. The annual growth rate is

not appropriate for rural residential subdivisions. Road geometry characteristics including pavement width, lane distribution on

multi lane roads and vehicle load factors. Typical road characteristics and traffic loadings for each of the road classifications are detailed in Table 3.2.


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Table 3.2 Typical Traffic Loadings on Rural Residential Roads Street Type

Bus Route

Growth Rate

Daily Traffic (vpd)

% CV Load Factor (ESA’s / CV)

Design Traffic Loading (ESA’s)

Rural Residential Access Court

No Nil 50 3 % 0.2 3.2 x 103

Rural Residential Street Through Traffic

No Nil 60 3 % 0.2 6.8 x 103

Rural Residential Road Through Traffic

Yes Nil 300 3 % 0.2 1.6 x 105

Collector Road Through Traffic

Yes Nil 500 3 % 0.2 1.7 x 105

3.3 Industrial Subdivision Roads

3.3.1 Road Geometry The industrial roads should be 10.0 metres wide with five metre wide verges on both sides of the road.

3.3.2 Calculation of Design Traffic Loading The calculation of the Design Traffic Loading (DTL) for the industrial subdivision roads should be carried out following a detailed traffic engineering assessment of the traffic impacts of the proposed development. The type of development will influence the type of vehicles, loading and predicted traffic volumes. The daily traffic generation rates for industrial developments detailed in the Roads and Traffic Authority, NSW ‘Guide to Traffic Engineering Developments’ provides some information on typical traffic volumes. A detailed assessment of the Design Traffic Loading for industrial subdivision pavements should address the following factors. Traffic generation of the proposed development including peak hour traffic

volumes and truck volumes. The peak period and daily volumes should be assigned to all sections of the road network.


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Details of the types of trucks that will use the roads and the proportion of vehicles that will be fully or partially loaded.

Access provisions to the proposed developments including turning templates for

the trucks accessing the loading areas. Information on changes in the truck usage patterns predicted over the design life

of the pavement. Assessment of load factors for all types of trucks. A method of calculating the

load factors (ESA’s / truck) is detailed in Appendix 7.6 of the Austroads Guide to the Structural Design of Road Pavements.

3.4 Design Traffic for Rigid Pavements The traffic loading used in the design of rigid pavements requires an estimate of the cumulative passes of each axle group type over the pavement and a distribution of loads in that axle group. The design loading on rigid pavements is expressed as the cumulative number of Commercial Vehicle Axle Groups (CVAGs) for each street type. As a guide, the Design Traffic (CVAGs) for each street type is detailed in Table 13.7.4 of the APRG Report No 21 ‘A Guide to the Design of New Pavements for Light Traffic’. The determination of the Design Traffic Loading (CVAGs) should include an allowance for construction traffic assuming an average number of Commercial Vehicle Axle Groups per truck of 2.0 for residential streets and 2.3 for rural areas. In the design of rigid pavements for industrial areas, an estimate of the CVAGs / CV should be determined from classified vehicle machine counts.


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4. Pavement Design

4.1 Pavement Design Life All flexible pavements shall be designed for a minimum design life of 25 years. Rigid pavements shall be designed for a service life of 40 years.

4.2 Design Reliability of Pavements The following design reliability shall be adopted for the design of subdivisional pavements in the Warrnambool City Council.

4.2.1 Urban Residential Pavements Granular pavements with a thin asphalt surfacing designed for use in urban residential subdivisions shall incorporate a Confidence Interval of 95 %. This Confidence interval assumes fixed level urban construction with good drainage and the availability of suitable pavement materials. The level of confidence indicates that the pavement will perform satisfactorily over the design period. The levels of surface rutting and roughness will remain within acceptable limits over the design life. If there are concerns about the design reliability of a pavement, multiplying the design traffic loading by a factor of up to five will increase the Confidence Interval. The pavement thicknesses detailed in Table 4.1 are based on the Figure 13.8.2 (a) of the APRG Report No 21.

4.2.2 Rural Residential Pavements Granular pavements with a sprayed seal surfacing designed for use in the rural residential subdivisions shall incorporate a Confidence Interval of 90 %. This lower level of confidence in the design represents the possibility of a future overlay to rehabilitate the pavement during the design life.

4.2.3 Industrial Subdivision Pavements Pavements for use in industrial subdivisions shall be designed by an approved Geotechnical Engineer using a mechanistic approach and shall incorporate a thick asphalt surfacing. The structural thickness determined from the mechanistic analysis shall be increased by 15 mm in accordance with Section 11.5 of the VicRoads RC 500.22 Code of Practice for Selection and Design of Pavements and Surfacing.

4.3 Flexible Pavement Thickness Design The pavement thickness design shall be determined from Tables 4.1 and 4.2 for Urban and Rural residential subdivisions.

4.3.1 Non Expansive Subgrades The total thickness detailed in Table 4.1 shall be used for pavements constructed on subgrades which are low reactive, low to moderate plasticity materials.


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Table 4.1 Pavement Thickness Design for Non Expansive Materials

Total Pavement Thickness (mm) Street Type CBR 2% CBR 3% CBR 4 % CBR 5 %

Urban Residential Streets Access Lane

400 320 300 300

Access Place

420 335 300 300


475 385 335 300


525 435 380 340


525 435 380 325


595 490 425 375

Arterial Road 645 540 470 415

Rural Residential Streets Rural Residential Access Court

425 330 300 300

Rural Residential Street

450 355 300 300

Rural Residential Through Road

560 470 395 340

Collector Road

565 470 400 345

4.3.2 Highly Reactive High Plasticity Subgrades Where the geotechnical testing has established that the subgrade is a highly reactive, high plasticity clay material, the total thickness of pavement shall be determined from Table 4.2. The design traffic loading will determine the minimum pavement cover over the expansive subgrade.


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Table 4.2 Pavement Thickness Design for Highly Reactive Materials

Total Pavement Thickness (mm) Street Type CBR 2% CBR 3% CBR 4 % CBR 5 %

Urban Residential Streets Access Lane

400 400 400 400

Access Place

420 400 400 400


475 400 400 400


525 435 400 400


525 435 400 400


595 490 425 410

Arterial Road 645 540 470 415

Rural Residential Streets Rural Residential Access Court

425 400 400 400

Rural Residential Street

450 400 400 400

Rural Residential Through Road

560 470 400 400

Collector Road

565 470 400 400

4.4 Pavement Composition

4.4.1 Urban Residential Streets The total pavement thickness determined from Tables 4.1 and 4.2 shall be constructed using the following pavement layers. This pavement composition shall ensure that the long term pavement performance standards are met and the pavements are practicable to construct. The composition of the pavements constructed for residential subdivisions in the Warrnambool City Council shall comply with following minimum requirements. The following pavement compositions are based on a Design Subgrade CBR of 4 %. For other Design Subgrade CBR values, the thickness of the lower subbase layer should be increased to provide the required total pavement thickness detailed in Tables 4.1 and 4.2.


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Access Lane, DTL > 7.4 x 103 ESA’s Surfacing 25 mm Size 10 Type L Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Subbase > 125 mm Subbase quality material with a Lab Soaked

CBR > 15 % and a history of proven performance.

Total >300 mm Access Place, DTL > 1.1 x 104 ESA’s Surfacing 25 mm Size 10 Type L Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Subbase > 125 mm Subbase quality material with a Lab Soaked

CBR > 15 % and a history of proven performance.

Total >300 mm Access Street – Level 1, DTL > 6.6 x 104 ESA’s Surfacing 25 mm Size 10 Type L Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Subbase > 160 mm Subbase quality material with a Lab Soaked

CBR > 15 % and a history of proven performance

Total > 335 mm Access Street – Level 2, DTL > 3.0 x 105 ESA’s Surfacing 25 mm Size 10 Type L Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 100 mm 20 mm Class 3 Crushed Rock or Class CC3

Crushed Concrete Lower Subbase > 105 mm Subbase quality material with a Lab Soaked


Total > 380 mm Collector Street – Level 1, DTL > 3.6 x 105 ESA’s Surfacing 35 mm Size 14 Type N Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 100 mm 20 mm Class 3 Crushed Rock or Class CC3

Crushed Concrete


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Lower Subbase > 105 mm Subbase quality material with a Lab Soaked CBR > 15 % and a history of proven performance

Total > 380 mm Collector Street – Level 2, DTL > 1.7 x 106 ESA’s Surfacing 35 mm Size 14 Type N Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 125 mm 20 mm Class 3 Crushed Rock or Class CC3



Total > 425 mm Arterial Road, DTL > 5.2 x 106 ESA’s Surfacing 35mm Size 14 Type N Asphalt Bituminous Prime Prime or Primerseal Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 150 mm 20 mm Class 3 Crushed Rock or Class CC3

Crushed Concrete Lower Subbase >135 mm Subbase quality material with a Lab Soaked


Total > 470 mm

4.4.2 Rural Residential Streets In rural residential subdivisions, the following minimum requirements shall be met for the composition of the pavements. Rural Residential Access Court, DTL > 3.2 x 103 ESA’s Seal Size 10 I T P & S Base Layer 150 mm 20 mm Class 2 Crushed Rock Subbase > 150 mm Subbase quality material with a Lab Soaked


Total > 300 mm Rural Residential Street, DTL > 6.8 x 103 ESA’s Seal Size 10 I T P & S Base Layer 150 mm 20 mm Class 2 Crushed Rock Subbase > 150 mm Subbase quality material with a Lab Soaked



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Total > 300 mm Rural Residential Through Road, DTL > 1.6 x 105 ESA’s Seal Size 14 I T P & S Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 100 mm 20 mm Class 3 Crushed Rock or Class CC3



Total > 395 mm Rural Residential Collector Road, DTL > 1.7 x 105 ESA’s Seal Size 14 I T P & S Base Layer 150 mm 20 mm Class 2 Crushed Rock Upper Subbase 100 mm 20 mm Class 3 Crushed Rock or Class CC3



Total > 400 mm

4.4.3 Industrial Subdivisions The pavement adopted for use in industrial subdivisions shall be designed by an approved Geotechnical Engineer using a mechanistic pavement design approach. Regardless of the results of this approach, the minimum thickness and composition for industrial pavements shall be as detailed below. The recommended pavement shall consist of a granular pavement with a thick asphalt surfacing. The following composition provides the minimum requirements for the heavy duty pavement. This design is based on a Design CBR of the subgrade of 4 %. Surfacing 35 mm Size 14 Type V (320) Asphalt Intermediate Layer > 65 mm Size 20 Type SI (320) Asphalt Base Layer 75 mm Size 20 Type SF(320) Asphalt Base 200 mm 20 mm Class 2 Crushed Rock Subbase > 170 mm Subbase quality material with a Lab Soaked


Total > 545 mm

4.4.4 Highly Reactive High Plasticity Subgrade Where the subgrade has been confirmed as being classified as a highly reactive, high plasticity clay subgrade, the pavement compositions detailed would be suitable. However, the subbase layer should be increased in thickness to provide the total pavement depth required.


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The minimum pavement thickness of 400 mm shall be used for the construction of residential pavements over moderately or highly expansive soils, regardless of the Design Traffic Loading. In addition, the following techniques shall be employed to minimise volume changes: Cut to fill shall be compacted at a moisture content close to the Standard

Optimum Moisture Content. Compaction of subgrade in cut areas shall be limited to that necessary to locate

weak areas requiring replacement. Construction techniques should limit the possibility of the subgrade drying out.

4.5 Subgrade Improvement Special treatments are required for subgrades which are soft and / or wet at the time of construction. For the purposes of this Design Guide, soft subgrades shall be regarded as soils having an in situ strength of less than CBR 2% and in situ moisture contents exceeding their Plastic Limit. Construction of pavements over soft subgrades will require some form of treatment or placement of an overlying working platform to enable placement and compaction of the subsequent pavement layers. The subgrade improvement layer may be incorporated into the pavement design in accordance with the following guidelines: Subgrade design CBR > 2 % The thickness of the working platform may be included in the overall pavement thickness provided the materials comply with the requirements of the guidelines. Subgrade design CBR < 2 % The pavement thickness design may be based on a subgrade design CBR of 2 % provided the subgrade is first improved to a depth of at least 150 mm and the subgrade improvement layer does not form part of the overall pavement thickness. Measures which may be employed to improve the subgrade to facilitate construction include the following: Draining and drying the subgrade. Excavation and replacement of the soft material with suitable material consisting

of at least 200 mm of unbound granular material. Provision of a gravel or rockfill working platform covered by an impermeable

layer. Stabilisation of the top layer of the subgrade to a depth of 200 mm. Use of geotextile membrane covered with a minimum thickness of 100 mm of

unbound granular material. The replacement of isolated areas of weak subgrade shall be treated by excavation to a sound base and backfilled to subgrade level with suitable earthworks materials from the site of with a Type A select fill with a permeability of < 1 x 10-7 cm/sec and a swell < 2.5 %. Where subgrade improvement layers are incorporated into the pavement structure, the usual requirements for compaction shall apply. Test rolling of the uppermost


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layer of the working platform shall be carried out to detect visible deformation and springing.

4.6 Rigid Pavement Design The design of rigid pavements shall be undertaken using the procedure detailed in Section 9 of the Austroads ‘Guide to the Structural Design of Road Pavements.’ A rigid pavement shall consist of a base layer of concrete which provides the structural capacity of the pavement with a subbase layer of either crushed rock, cement bound crushed rock or lean mix concrete. The subbase layer provides uniform support for the concrete base layer. In areas with a weak subgrade, a lower subbase layer or stabilisation of the subgrade will be required. Thickness Design Charts for traffic loadings expected in residential streets are attached in Section 13 of the APRG Report No 21. All calculations of the design traffic loadings and the slab thickness design shall be submitted for projects proposing a rigid pavement in the Hume City Council. Details of the slab reinforcement, joint spacing, contraction and longitudinal joint details and layout plans of the joints shall also be provided.

4.7 Intersections At intersections subject to a high volume of braking vehicles and turning traffic, an asphalt surfacing should be placed at, and on the approaches to the intersection. The surfacing should consist of a 35 mm thick layer of Size 14 Type V (320) asphalt. The asphalt layer should extend for 50 metres or to the end of the right turn lanes on the approaches and for 20 metres on the departure side of the intersection. At the intersections of the local streets (Access Lanes, Access Places and Access Streets), the asphalt surfacing on the approach roads of 25 mm thick layer of Size 10 asphalt should be extended through the intersections.

4.8 Roundabouts At roundabouts subject to a high volume of turning traffic and use by heavy vehicles, the asphalt surfacing should consist of Size 14 Type V (320) asphalt or a polymer modified asphalt with a Class A10E polymer modified binder. A prime should be applied to the crushed rock base layer prior to applying the asphalt surfacing. The design of the pavement for the roundabout should use the presumptive moduli for thew asphalt using a design speed of 10 km/h.


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5. Pavement Materials The pavement materials used in the construction of pavements shall comply with the requirements of the VicRoads Standard Specifications for Roadworks and Bridgeworks and standard clauses in the Warrnambool City Council Specifications.

5.1 Asphalt Surfacing It is important to specify the appropriate type of asphalt to suit the required purpose. Improper selection of asphalt may lead to premature distress or failure. The following types of asphalt are regularly used in VicRoads projects. Asphalt Type L A light duty asphalt designed for lightly trafficked roads such as

private streets and carparks. It has a higher bitumen content with low voids to reduce the rate of oxidation and increase the service life.

Asphalt Type N A normal duty asphalt suitable for wearing, intermediate and

base courses for the majority of roads. Asphalt Type H A heavy duty wearing course asphalt for roads with high traffic

volumes. It has Class 320 bitumen and a higher quality aggregate than Type N.

Asphalt Type V A heavy duty wearing course asphalt with a higher percentage

of air voids to increase stability to resist rutting and maintain good skid resistance at heavily trafficked intersections and roundabouts. Type V asphalt is normally placed on the intersection approaches from the start of the turn lane taper or a minimum of 50 metres from the stop line and extending through the intersection to at least 20 metres of the departure lanes.

Asphalt Type SI A multi purpose Size 14 or Size 20 structural asphalt for

intermediate course asphalt in heavy duty pavements. Asphalt Type SF A bitumen enriched layer with a higher bitumen content to

increase pavement fatigue life for pavements designed with a total asphalt depth of over 175 mm. The Type R asphalt is used as a Size 20 asphalt in the base layer of deep lift asphalt pavements and requires at least 24 hours to cure prior to placing the subsequent layers. The thickness of the Type R layer is limited to 75 mm and should have a minimum thickness of asphalt cover of 100 mm.

Special Asphalt Mixes In some cases it maybe appropriate to use special mixes of

asphalt such as Open Graded Friction Course asphalt, Crumbed Rubber asphalt, Polymer Modified Asphalt, Lean Mix asphalt. These asphalt mixes have particular requirements for their use.


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The performance of an asphalt pavement or surfacing can be significantly reduced if the thickness of the asphalt layer does not match the asphalt size. Generally, to avoid dragging or ‘boney’ areas, the asphalt depth should not be less than 2.5 times the nominal size of the aggregate. Also, to ensure the asphalt layer has high strength and stability, the depth of the asphalt should not exceed five times the nominal size of the aggregate. As a guide, the appropriate size of asphalt or layer thickness is detailed in Table 5.1. Table 5.1 Appropriate Asphalt Layer Thickness. Nominal Size Courses where Used Depth Range

7 Wearing course and regulation 15 to 25 mm 10 Wearing course and regulation 25 to 35 mm 14 Wearing, intermediate and regulation 35 to 50 mm 20 Base, intermediate and regulation 50 to 100 mm

5.2 Bituminous Prime A bituminous prime or primerseal shall be applied to the top of the base course crushed rock layer. Its role is to bind the asphalt surfacing to the crushed rock layer and to waterproof the pavement. A prime will take at least 48 hours to dry before trafficking and up to 5 days to cure. If the road has to be opened to traffic within this time, a primerseal should be applied. The asphalt surfacing should not be applied over a primerseal for at least 48 hours unless approved by the superintendent. The prime shall consist of a light grade primer AMC0 applied at a rate of 0.5 to 1.1 litres / m2

The primerseal shall consist of a CRS Bitumen Emulsion applied at a rate of 1.3 litres / m2 and covered with Size 7 aggregate.

5.3 Granular Pavement Materials The granular pavement materials used for the Base and the Upper Subbase layers shall conform to the requirements of the VicRoads Standard Specifications for Road and Bridgeworks. The 20 mm crushed rock from the Tarrone Quarry produces material complying with the requirements of Class 2 and Class 3 crushed rock. If an alternative source for the crushed rock material is to be used, appropriate test results should be provided to the Council.

5.4 Subbase Materials The material to be used for the lower subbase layers may consist of the following: Quarry produced crushed rock

Crushed rock materials complying with the requirements of the VicRoads Standard Specifications for Roadworks and Bridgeworks.

Limestone and Scoria / Tuff materials


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Limestone and scoria / tuff materials having a Laboratory Soaked CBR > 15% and a history of proven performance. Most of the material currently used in the Warrnambool area would meet the requirements for a subbase material. Excessive watering and over working of scoria / tuff materials should be avoided as it may effect the strength of the material.

Insitu lime or cement stabilised materials The insitu stabilisation of subgrade materials with either lime or cement should be based on laboratory testing of the subgrade materials. As a guide, the maximum CBR to be assigned to the stabilised layer for the purposes of the pavement thickness design shall be 8 % for materials stabilised with lime only 10 % for materials stabilised with lime and cement

Crushed concrete Recycled crushed concrete may be used as a subbase material. The grading of the crushed concrete should comply with Section 820 of the VicRoads Standard Specifications for Roadworks and Bridgeworks.

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6. Subsurface Drainage

6.1 General Subsurface drains are an important part of the control of moisture for a pavement and the surrounding materials. The objectives of subsurface drainage design are to maintain pavement strength and durability by: Minimising the opportunities for groundwater to enter the pavement. Collecting and conveying infiltrated surface water to an outlet. Protecting the subgrade The design of the subsurface drainage should be carried out in accordance with the following: VicRoads Technical Bulletin No 32 ‘Drainage of Subsurface Water from Roads’. VicRoads Road Design Guidelines – Drainage

6.2 Types of Subsurface Drains

6.2.1 Longitudinal Pavement Drains Longitudinal subsurface drains shall be located as follows: Along the low sides of the pavement. Along both sides of the pavement in cut near any cut to fill line. Along both sides of the pavement with kerb and channel. Along both sides of the pavement where the cross slope is less than 0.02 m/m. On the high side of the pavement where seepage is evident, or where water may

enter from batters, full width pavement, service trenches or abutting properties. Along the joins between an existing pavement and a pavement widening where

pavement depths or permeability could trap moisture.

6.2.2 Transverse Pavement Drains Transverse pavement drains shall be located as follows On the upstream side of a cut to fill line Along changes in pavement depth or permeability. At both ends of bridges and approach slabs. At superelevation changes to limit the length of the drainage path.

6.2.3 Rural Roads Subsurface drains are not normally placed along lightly trafficked rural roads except where the subgrade consists of granitic sands mixed with rock.

6.3 Location of Subsurface Drains The longitudinal subsurface drains should be installed beneath the kerb and channel with the far edge of the trench along the line of the back of the kerb and channel. The centreline of the pipe should be installed in the middle of the trench. At stormwater drainage pits, the subsurface drain should be connected through the pit wall.

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The trench should be at least 300 mm wide and the pipe installed at least 200 mm below the subgrade level. The invert level of the pipe should be at least 25 mm above the base of the trench. If the subgrade was determined to be a moderate to highly expansive material, the subsurface drainage should be installed within the lower subbase layer. The invert of the pipe should be at least 100 mm above the base of the trench. Increasing the thickness of the lower subbase layer may be required for a width of at least two metres from the subsurface drain to ensure adequate cover over the subsurface drains.

6.4 Type of Subsurface Drains The type of subsurface drains adopted will depend on the grading of the adjacent materials and the size of the pipe perforations. In areas with fine grained materials such as silts and clays, a coarse washed sand is usually specified. These subgrade materials are non–dispersive and a filter sock on a corrugated PVC pipe is usually adopted for the subsurface drainage. In other areas, the grading of the subgrade soil must be known.

Documents

Pavement Design Guidelines Rev A - City of Warrnambool · PDF fileinvestigations, structural design, pavement composition, acceptable materials and construction practices to be adopted