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PAVEMENT DESIGN

TOWN OF BUCKEYE

PUBLIC WORKS

423 Az Eastern Ave.

Buckeye, AZ 85326

623.349.6800

TOWN OF BUCKEYE ENGINEERING DESIGN STANDARDS

MANUAL

June 2007

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Town of Buckeye Engineering DivisionPublic Works

pavement Design Design Manual #206 Transportation Standards

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1.1 Introduction

1.1-1 This manual, provided by the Town of Buckeye Public Works Department,is the essential information and policy needed for designing structuralsections of flexible pavements (Asphalt Concrete Cement, ACC)constructed within the Towns public rights-of-way. Developers of privateproperty do this construction as a condition of development as stipulatedby the Town for work within the Town limits of incorporation.

1.2 Aspha lt Cem ent Conc rete

1.2-1 The asphalt concrete portion of a flexible pavement shall have aminimum depth, number of courses, and mix design called for by streetclassification (i.e., Major and Minor Arterial, Collector and Local Road).The mix design references are excerpted from the East Valley AsphaltCommittee Design Standards and from Section 710 of the MAGSpecifications and the City of Scottsdale (COS) Supplements to MAG andCity of Phoenix Asphaltic Concrete Design Specifications. Mix designs

and course thicknesses other than those specified in the table below maynot be used unless approval to do so is provided by the Town. Minimumlift thicknesses are also outlined in Table 710-1 of the COS Supplements toMAG Specifications. The mix design and course thicknesses shall beclearly indicated on paving plans for public rights-of-way improvements.

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1.3-2 The following tests are required for design procedures indicated in thismanual and must be performed in accordance with the AmericanSociety for Testing Materials (ASTM) procedures.

a) In order to use the base course design standards and policies for localroads described under Sec tion 1.4-1 , the following tests are required:

1. Sieve analysis of each roadbed soil sample is needed todetermine thepercent passing the #200 sieve.

2. Atterberg-Limits tests are needed for each sample: (The liquidLimit, (LL) and plastic limit, (PL) used to establish the plasticityindex.) High liquid limits typically indicate high clay content soilsthat are not suitable roadbed soils. Conversely, low liquid limitsoils typically have low clay content and are suitable for

roadbed soils.

b) In order to use the base course design procedures for major streetsdescribed under Sec tion 1.1-5 , or in order to use the structuralsection design procedures described under Sec tion 1.6 , R-valuetesting is required.

1. R-value determination shall be made for exudation pressure of3000 psi. Each pavement thickness design must be based on theR-values determined by the tests, and for each length ofpavement to be constructed with a constant thickness design, thelowest R-value within that length of pavement will be used. If theengineer elects not to run R-value tests on every subgradesample, the design report must indicate the basis on which theengineer selected the samples for the R-value tests.

c) Swelling tests are needed if the soil type indicates the presence of soilstending to swell significantly with added moisture.

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1.3-3 A pavement design report shall be required for each development or project in which paving within the public rights-of-way shall be done. Thisreport must be submitted with the paving plans (or shall be a part ofthem) and it must describe the soil test results and design choices. Thereport shall contain the additional minimum items listed below:

a) A map of the project area showing identification and location of eachsample taken.

b) A description of the soil conditions.

c) A statement of conclusions applicable to the pavement design.

d) A listing of the test results on each sample.

1.4 Base Course Design Thic kness for Loc al Roads andCollectors

1.4-1 There are two design charts for base course thickness design, one for thelocal road and one for the collector street.

a) Figure 1-1 is a chart for the design of base course thicknesses for Local Residential Streets.

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Figure 1-1 Minimum Dep th of Base Course for Loc al Roa ds

b) Figure 1-2 is a chart for the design of base course thicknesses for:

1. Collector Streets2. Commercial Collector Streets3. Industrial Collector Streets

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Figure 1-2 Minimum Depth of Base Course for Collector Com me rc ial Collec tor and Industrial Collector Streets

1.5 Base Course Design Thic kness for Arterial Roads

1.5-1 The base course depths listed in Table 1-1 below are arranged inaccordance with the street classifications and the R-values determined insubgrade testing. The depths are determined by the procedures used for the design of structural sections (Modified AASHTO Pavement Design)described in Section 1.6 . For a given street classification, the street withthe heaviest current and projected traffic loading was used to determine

the range of base course depths for all streets of that classification;therefore, the base course depths listed in this chart will provideconservative pavement designs.

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INDEX TRANSPORTATION

DM 206 PAVEMENT DESIGN

1.1 INTRODUCTION .......................................................................................... 2

1.2 ASPHALT CEMENT CONCRETE................................................................... 2

1.3 SOIL TESTING REQUIREMENTS-SUBGRADE.................................................. 3

1.4 BASE COURSE DESIGN THICKNESS FOR LOCAL ROADS AND

COLLECTORS........................................................................................................ 5

1.5 BASE COURSE DESIGN THICKNESS FOR ARTERIALS ROADS....................... 7

1.6 STRUCTURAL DESIGN OF PAVEMENT SECTIONS - MODIFIED A ASHTO

PAVEMENT DESIGN ............................................................................................. 8

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R-Values

Street Classification0 -5

5 -10

10-

15

15-

20

20-

25

25-

30

30-

35

35-

40

40-

45

45-

50

50+

Minor Arterials, MajorArterials and Parkways 29 27 25 23 20 18 16 14 12 10 9

Tab le 1-1 Minimum Depth o f Base Co urse for Arterial Roa ds

1.5-2 When design constraints make it necessary to reduce the overall structuralpavement section (and at the discretion of the Town), the total structuralpavement section depth determined from the use of Figure 1-1, Figure 1-2and Table 1-1 shall be substituted with additional asphalt cementconcrete over aggregate base material. A deeper asphalt cement

concrete section can be used in replacement of some or all of theaggregate base material at a rate of 1 inch of asphalt cement concretefor every 3 inches of aggregate base material.

1.6 Struc tural Design of Pavement Sec tions ADOT Modified

AASHTO Pave ment Design

1.6-1 The American Association of State Highway and Transportation Officials(AASHTO) published a guide for the design of pavement structures in 1961and a revised guide in 1972. The Arizona Department of Transportation(ADOT) modified the procedures provided in the AASHTO design guide tomeet requirements for the State of Arizona. The City of Phoenix uses theADOT modified procedures and has selected certain design coefficientsappropriate to the Phoenix metropolitan area. The City of Scottsdale alsouses the ADOT modified procedures with the City of Phoenix coefficients.

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1.6-2 ADOT uses its own adoption of the procedures outlined in the AASHTOGuide for Design of Pavement Structures published in 1961 and revised in1972. The following assumptions must be made:

a) The soil support capacity of the subgrade soils can be predictedadequately by testing to determine R-values.

b) The R-values can be effectively related to a soil-bearing capacityrating scale called the soil support value (SS) or the resilient modulus.

c) A suitable pavement depth is determined by a procedure thatconsiders the soil support value in conjunction with projected trafficloading, environmental conditions, and weighted structural values for the various components of the pavement structure.

1.6-3 DESIGN PARAMETERS

a) Subg rade Supp ort Value

1. The subgrade support value represents the bearing capacity of theroadbed subgrade soil. It is determined by a relationship establishedbetween its scale and the measured or correlated R-value scale, asshown in Table 1-2 This relationship is not uniform throughout thecountry. ADOT has established the relationship determined by thefollowing equation.

SS = 0.094R + 1.75Where:

SS = Soil Support Value and R = R Value

b) Pavement Serviceability Index

1. The Pavement Serviceability Index (PSI) is a value that represents thesurface condition of roadway in terms of rideability or roughness andthe distresses associated with it, such as cracking, patching, rutting,raveling, depressions, swelling, etc, during some point of the pavementdesign life. It is used in the design equation to represent the theoreticalloss of serviceability over a 20-year design period, from the time ofcompleted construction. The Town shall use an Initial ServiceabilityIndex (PSI I) of 5.0. The Terminal Serviceability Index (PSI t) varies,depending upon the level of service desired. Most pavements have a

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normal distribution of reliability requiring some sort of rehabilitation athalf of design life. The Town shall use a Terminal Serviceability Indexof 2.5. Table 1-2 below lists the material R-Value and its correlatedsubgrage support value used in determining the structural number for pavement section design thicknesses.

Table 1-2 ADOT Ma terial Servic es R-Values and Soil Support Value Rela tionships

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c ) Reg iona l Fac tor

1. The Pavement within the Phoenix Metropolitan area typically does notexperience climatic changes that rapidly degrade pavement

structures,such as large amounts of rain or freeze-thaw cycles. For this reason, aRegional Factor of 1.0 shall be used.

d) The Structural Num ber

1. The Structural Number (SN) is derived from an analysis of traffic,subgrade soil conditions, environmental conditions, and is used inconjunction with structural layer coefficients (related to the type ofmaterial to be used in each layer) to calculate the thickness of aflexible pavement structure consisting of various flexible layers. The

following equation is for determining the structural number developed from data accumulated by AASHTO:

.and

Since SN appears on both sides of the equation, the solution canbe most rapidly done by nomograph. Figure 1-3 is a nomographdeveloped by ADOT for this purpose, with a Terminal Servic ea bilityIndex of 2.5 and a Regional Factor of 1.0 .

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Figure 1-3 Flexible Pavements ADOT Modified AA SHTO Nomog rap h for Structural Numb er (SN) Determination

1.6-4 PROJECTED TRAFFIC LOADING CLASSIFICATION DATA

Traffic loading for flexible pavement design shall be on the basis of thecumulative damage caused by passenger, single-unit and multi-unitvehicles. Examples of such vehicles classifications are as follows:

Multi-Unit Trucks with tractor-trailers, tandem and tridem(MU) trailers with single, or dual wheel-single, tandem,

tridem axle configurations that have an articulatingtractor and trailer combination.

Single-Unit - Trucks that typically have no articulation and can(SU) have single or dual wheel single, tandem, or tridem

axle configurations such as refuse or dump trucks,water trucks delivery box trucks, fire trucks schoolbusses.

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Passenger - Any vehicle that is not within the above mentionedVehicles class, such as cars and pickup trucks.(PV)

1.6-5 Vehicular distribution of traffic shall come from traffic data that may beavailable from one or more of the following sources:

1. Maricopa Association of Governments (MAG) Traffic Projections

2. Traffic studies provided for the project either in Design ConceptReport (DCR), or

3. Scope of Work (typically for design consultants)

1.6-6 Calculate the 18Kip Equivalent Single-Axle Load (ESAL) applications using

the vehicle distribution percentages determined by a traffic survey andthe 18Kip single-axle load for each type of vehicle listed below in Table 1-3 .

Class Typ e of Vehic le18Kip Equiv.Single-

Axle Load(ESAL) Fac tor

C Passenger cars 0.0008

2P Light 4-tire trucks 0.0012

2S Heavy 4-tire trucks 0.0058

2D 2-axle, 6-tire trucks 0.1632

B Busses 0.2500

3D 3-axle trucks 0.5987

2S1 2-axle tractor, 1-axle semi-trailer 0.4082



2-2 2-axle truck, 2-axle semi-trailer 0.3043

3-2 3-axle truck, 2-axle full trailer 0.9368

3-3 3-axle truck, 3-axle full trailer 0.9368

2S1-22-axle tractor, 1-axle semi-trailer, 2-axle fulltrailer 0.8467

3S1-2 3-axle tractor, 1-axle semi-trailer, 2-axle fulltrailer 0.9580

Tab le 1-3 18Kip Equiva lent Single Axle Loa d Fac tor by Typ e of Vehic le

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1.6-7 For streets with more than one lane in each direction, multiply the ESALcalculated in Section 1.6-4 above by the following appropriate factor below in Table 1-4 to calculate the cumulative design lane loading:

Numb er of Lane s inEac h Direc tion

Percent o f 18-k ip ESALsin Design Lane (D L)

1 100

2 90

3 or 4 70

Table 1-4 Design Lane Traffic Distribution

1.6-8 The design direction distribution factor (D D) is typically 50% (D D=0.5) for most roadways. However, there are instances where land uses or connectivity may result in predominant design traffic flow in one directionover the other. In those instances the design direction distribution mayvary from 0.5 0.7 or as determined in a traffic study.

1.6-9 The Design life shall be 20 years and shall have 365 days per year beforeapplying a traffic growth factor.

1.6-10 The traffic growth factor shall be used to forecast annual traffic growth for each year of the pavement design life plus accounting for any growthbetween planning and final implementation of the roadway facility (i.e.,deferred implementation). Existing traffic data shall not only for a 20 year design life, but also account for any preliminary traffic growth prior account to the facility being open for public use, that may affect thereasonable forecast of future traffic loading. The following equationbelow shall be used to calculate traffic growth:

GF = (1.0 + 5%) n

Where n = the number of design years(Note: adjust if needed for deferred implementation)

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1.6-11 The sum of all such loads is the 18Kip Equivalent Single Axle Load (ESAL) ofall vehicle classifications traveling the road. This sum must be multiplied bythe average ADT for traffic; then multiplied by the design lane distributionand directional factors; days in a year and 20 year design life andaccounting for a growth factor. The equation below illustrates theprocess:

ESAL = A DT * (ESAL Fac to r) * D D * DL * 365da ys * 20 design ye ars * GF

1.6-12 PROJECTED TRAFFIC LOADING NO CLASSIFICATION DATA

In the event that ADT data is available but no sufficient vehicular classifications can be obtained, the following traffic equivalency factorsshall be applied. The traffic adjustment factors shown below in Table 1-5

shall be used.

Typ e o f Vehic le(ESAL) TrafficAdjustment

FactorPassenger

Vehicles (PV) 0.0008

Single-UnitVehicles (SU)

Multi-UnitVehicles (MU)

1.50

Table 1-5 18kip Equiva lent- Single Axle Loa d (ESAL)(when vehic le c lassifica tion is not known)

1.6-13 If vehicle classification data is not available in sufficient detail to use thestandard classifications described above, a traffic equivalency factor of1.50 shall be applied to the percentage of vehicles considered to beheavy trucks ( Class 2D). The designer shall notice that passenger vehicles shall carry the same factor in both cases (with classification dataand no classification data) and is not affected by the lack of vehicular classification. This approximation method is described in the ADOTPreliminary Engineering and Design Manual.

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1.6-14 The remaining percentage of vehicles is considered to be passenger vehicles. The design procedure for ESAL calculations is calculated in thesame way as mentioned above in Section 1.6-11 , except now thereremain only TWO classifications (cars and heavy trucks). Cars are assigneda 0.0008 factor and heavy trucks are assigned a factor of 1.50. Theformula below illustrates the adjusted method.

ESAL = [ADT * (%Pass. Veh) * 0.0008] + [ADT * (%Hea vy Truc ks) * 1.50)]

(Note: Illustration only, does not include days per year, 20 year life design direction, design lane distribution and growth factor)

1.6-15 STRUCTURAL DESIGN THICKNESS EQUATION

Once a structural number is determined for the initial pavement structure,it shall be checked against the minimum SN value for asphalt and basecourse requirements for that facility, it shall be necessary to select a

structural set of design thicknesses to satisfy the minimum calculatedstructural number (SN) requirement for given traffic and soil loadingconditions plotted from the input values from the above Figure 1-3 nomograph.

1.6-16 The structural number is a function of the layer coefficient, designthicknesses, and drainage coefficients. The layer coefficient a n is themeasure of the relative ability of a unit thickness of pavement structuralmaterial to function as its intended structural layer component. Thecomponents of the pavement structure are assigned structuralcoefficients values and shall be used as parameters in conjunction with astructural number in developing the design of pavement sections. Thecoefficients shown below were developed by the City of Phoenix fromexperience, tests, and correlation with information in ADOT designmanuals and MAG Specifications.

Pavem ent Lay er Com ponent ADOT Rang e Lay er Coe ffic ient

Asphaltic Concrete (plant mix) 0.34 to 0.46 0.39

Bituminous Treated Base 0.30 to 0.35 0.31

Cement Treated Base 0.15 to 0.29 0.23

Aggregate Base 0.08 to 0.14 0.11**As modified by the Town of Buckeye

Table 1-6 Structural Layer Coe ffic ients (a n )

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1.6-17 The layer drainage coefficient m n is the measure of the relative ability of aunit thickness of pavement structural material to drain water from its layer over time. The rating is based upon the following criteria in the tablebelow:

Layer Drainage Quality DrainageCoefficient ADOTWate r Rem ovedwithin AASHTO

Excellent 1.15 2 hours

Good 1.07 1 day

Fair 1.00 1 week

Poor 0.93 1 month

Very Poor 0.86 Water will notdrain

Tab le 1-7 Drainag e Lay er Coefficients (m n )

1.6-18 The Structural design layer thicknesses are then determined by theAASHTO Design Equation as shown:

SN = a 1D1 + a 2D2m 2 + a 2D2m 2 + a nDnm n

Where:

SN = Structural Number of Pavement obtained from nomograph.

a 1, a 2, a 3,.. a n = structural layer coefficients for the surface, base,sub-base and n sub-base respectively.

D1, D 2, D 3 D n = structural layer design thicknesses for thesurface, base, sub-base and n sub-base respectively.

m 2, m 3..m n = layer drainage coefficients for the base, sub-base andn sub-base respectively.

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1.6-19 The Town shall have the minimum thickness of pavement layers basedupon the minimum Asphalt Cement Concrete (ACC) and AggregateBase Course (ABC) as indicated in the previous sections. Thecorresponding minimum Structural Numbers shall directly apply from theminimum layer requirements based upon back calculations a n , SN valuesfrom the minimum pavement layer thicknesses (ACC & ABC).

Roadway Classific ation

MinimumACC

Thic kness (Inches)

MinimumABC

Thic kness(Inches)

Minimum StructuralNumber SN

Local Road 3 6 1.83

Collector and IndustrialCollector 5 6 2.61

Minor and Major Arterials 6 9 3.53

Parkways 6 9 3.53

Table 1-8 Minim um Flexible Pavement Design Thic kness Laye rs

1.6-20 The information contained in this manual is a compilation of excerpts fromthe following agencies and/or authorities most current edition of their respective publications insofar as applicable:

Fed eral Highwa y A dministrat ion (FHWA)Am eric an Assoc iation o f Sta te Highw ay Transporta tion Offic ia ls (AASHTO)Arizona Dep artm ent of Tra nsporta tion (ADOT)Ma ric op a Co unty Depa rtm ent o f Tra nsportation (MC DOT)Maricopa Association of Governments (MAG)

1.6-21 Additional information contained in this manual is a compilation ofexcerpts from the following approved planning, framework study, policyguidelines, specifications and design criteria standards at the municipal

level:

City o f Sc ot tsda le, A rizona City of Phoenix, Arizona

Documents

DM206 6-18-07