pavement-design

University of Nevada Reno, UNR

CEE 427

1

CEE 427 PAVEMENT DESIGN

Spring 2011 Instructors: Peter E. Sebaaly & Elie Y. Hajj, Ph.D. SEM Bldg, Room 320A Tel: (775) 784-1180

Pavement Design 2

Pavement Design

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CEE 427

Early Pavement Consideration 3

 





Getting people out of the mud Quality HMA mixes was not a major issue Mix design concepts were simple Traffic levels were generally g y low

Definition 4

Pavement Design

Pavement Design

Pavement

Design

- Upper part of roadway, airport, or parking area structure - Includes all layers resting on the original ground - Consists of all structural elements or layers, including shoulders

- Conceived/ developed plan for something to serve a specific function

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CEE 427

Pavement Design 5

 Solves

for thickness required q to carryy loads under material & environmental conditions

M t i l Materials Climate

L d Load D1 ? D2 ? D3 ?

Pavement Design Vs Other Civil Structures 6







Pavement Design

Most civil structures either fail immediately or last for ever. Pavements deteriorate gradually over many years, as a function of materials quality, traffic loading, and environmental influences. Therefore pavement design should be capable of predicting the long term performance of the pavement: not a sudden failure, but a slow progress toward failure.

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CEE 427

Pavement Types 7

I.

Flexible Pavement: Asphalt Concrete (AC) Pavements (mixture of asphalt and stones - HMA): A. Conventional Asphalt Pavements B. Full-Depth Asphalt Pavements

II.

Rigid Pavements: Portland Cement Concrete (PCC) Pavements (mixture of Portland cement, water, and stones)

III.

Composite Pavements: Composed of both HMA and PCC

I. Flexible Pavement Types 8



Flexible Pavement: Asphalt Concrete (AC) Pavements (mixture of asphalt and stones - HMA): A. Conventional Asphalt Pavements B Full-Depth B. Full Depth Asphalt Pavements

Pavement Design

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CEE 427

A. Conventional Asphalt Pavements 9

Seal Coat Tack Coat Prime Coat

Quality

Wearing Course (1”-2”) Binder Course (2”-4”) Crushed Aggregate Base - CAB Gravel or lower quality of crushed aggregate

Base Course (4”-12”) Subbase Course (4”-12”) Compacted Subgrade ( 6”) Natural Subgrade


Asphalt concrete Seal coat: thin coat of liquid asphalt + spread of aggregates 

Wearing course: top course of asphalt pavement - usually dense graded HMA - resist distortion under traffic - provide smooth & skid-resistant riding surface - waterproof to protect pavement and SG.

Binder course: HMA too thick to be compacted in one layer, larger size aggregates (NDOT compact max. 2” at a time)

Pavement Design

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CEE 427




Tack Coat: asphalt emulsion diluted with water bond between surface being paved and overlying course very thin & uniformly cover entire surface.



Prime Coat: low-viscosity cutback asphalt applied to an absorbent bsorbent surface. s rf e

Prime Coat vs. Tack Coat 12

Prime coat penetrates into underlying layer, plugs voids, and forms watertight surface

Tack coat does not require the penetration of asphalt into the underlying layer

Pavement Design

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CEE 427

B. Full-Depth Asphalt Pavements 13

 

Cost-effective for heavy traffic L l materials Local i l not available il bl Prime Coat Asphalt Wearing Course Asphalt Binder Course Prepared Subgrade Natural Subgrade

II. Rigid Pavement Types 14

PCC Slab Base or Subbase Course Subgrade

Base course will not contribute to the structural capacity of the pavement system. Base course used to: o Control pumping o Control frost action o Drainage layer o Control shrinkage & swelling of SG o Construction platform.

Pavement Design

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CEE 427




JPCP: Jointed Plain Concrete Pavement



JRCP: Jointed Reinforced Concrete Pavement



CRCP: Continuously Reinforced Concrete Pavement




Pavement Design

JPCP: Jointed Plain Concrete Pavement

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CEE 427




JRCP: Jointed Reinforced Concrete Pavement




Pavement Design

CRCP: Continuously Reinforced Concrete Pavement

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CEE 427

Rigid Pavements – Tie Bars 19

Rigid Pavements – Dowel Bars 20

• Coated with stainless steel or epoxy p y in order to pprevent corrosion. • Usually inserted at mid-slab depth and coated with a bondbreaking substance to prevent bonding to the PCC. • Dowels help transfer load but allow adjacent slabs to expand and contract independent of one another.

Pavement Design

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CEE 427

How Do Asphalt Pavement Fails 21

22

Occurs at High Temperature

Pavement Design

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24

Occurs at Intermediate Temperature

Pavement Design

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FATIGUE CRACKING

26

LOW TEMPERATURE CRACKING

Pavement Design

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CEE 427

How Do Rigid Pavement Fails 27

28

Pavement Design

Transverse Cracking

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Longitudinal Cracking

30

Pavement Design

Pumping

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32

Pavement Design

CEE 427

Joint Faulting

Corner Break

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Joint Spalling

33

Pavement Design Methods 34



AASHTO Design Procedure (1993) (American Association of State Highway and Transportation Officials).

Pavement Design



Asphalt Institute (AI) Pavement Design Procedure.

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CEE 427

AASHTO 1993 Pavement Design Guide Input parameters 35

Pavement Performance - Serviceability 36

  

Pavement Design

Serviceability index that range from 0 – 5 describes pavement condition p pi = initial serviceability  condition of the pavement immediately after construction (pi = 4.2) pt = terminal serviceability  condition of the pavement at the end of performance life F ti l classification Functional l ifi ti

T Terminal i l serviceability i bilit pt

Interstate Principal arterials Collectors/locals

3.0 2.5 2.0

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CEE 427

Pavement Performance – Serviceability (cont’d) 37



Serviceability Loss:

psi = pi – pt = difference between initial serviceability index and terminal serviceability index Ex: for Principal Arterials psi = pi – pt = 4.2 – 2.5 = 1.7

AASHTO 1993 Pavement Design Guide 38

Pavement Design

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CEE 427

Traffic Characterization 39



Most important factor in pavement design



Traffic consideration include: - Loading magnitude and configuration - Number of load repetitions

Traffic Characterization Axle Configuration 40

Single axle single tire

Tandem axles single tires

Pavement Design

Single axle dual tires

Tandem axles dual tires

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CEE 427

Traffic Characterization FHWA Vehicle Classification 41

1) Motor cycles 2) Passenger Cars 3) Other 2-axle, 4 tire single unit veh. 4) Buses 5) 2-axle single tire, single unit truck 6) 3-axle single unit trucks 7)  4 single axle single unit trucks 8)  4 axle single trailer trucks 9) 5-axle single trailer trucks 10)  6 axle single trailer trucks 11)  5 axle multi-trailer trucks 12) 6-axle multi trailer trucks 13)  7 axle multi-trailer trucks

Traffic Load 42

FHWA Class 8 (4 or less axle single trailer trucks) FHWA Class 10 (6 or more axle single trailer trucks)

Pavement Design

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CEE 427

Traffic Load 43

FHWA Class 11 (5 or less axle multi-trailer trucks)

FHWA Class 13 (7 or more axle multi-trailer trucks)

Traffic Load 44

Tractor Semi-trailer 18-wheeler truck

Pavement Design

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CEE 427




Design thickness: number of repetitions of a standard single axle load (18 kip = 80 kN). kN)



Any axle/wheel configuration (axle not 18 kip or consists of tandem or tridem axles) is converted to equivalent single axle load (18 kip) by multiplying the number of repetitions p of each configuration g byy its equivalent axle load factor (EALF).



Obtain the equivalent effect based on 18-kip (80 kN) single-axle load – equivalent single axle loads (ESAL)




ESAL for Design Lane

ESAL  ADT 0 T Tf G D L 365Y  ADT = Average Daily Traffic T = truck percentage Tf = truck factor (ESALs/truck) G = growth factor D = directional distribution factor (usually 0.5) L = lane distribution factor (varies with volume of traffic & # of lanes) Y = design period in years

Pavement Design

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CEE 427

Traffic Characterization

Truck Factor Tf 47



 

single Tf can be applied to all trucks or separate Tf can be used for different truck classes (applicable if different truck growth factors) Use same growth factor for all trucks & a single Tf Tf could be found from: o

Traffic data: # axles for each load group & #of trucks weighed Tf = (ESALs ( for all trucks weighed)/(No. g ) ( trucks weighed) g )

o

NDOT Vehicle Classification report (www.nevadadot.com/reports_pubs/Traffic_Report/)

o

Distribution of truck factors for different classes of highways and vehicles in the US.

Traffic Characterization

Truck Factor Tf 48



AASHTO Equivalent Factors – Example: 18-wheeler truck

30 kips/axle

34 kips/axle 14 kips/axle

0.79 ESAL + 1.15 ESAL + 0.47 ESAL

Total equivalent damage by this truck is (pt = 3.0, SN = 3):

Pavement Design

2.41 ESALs/Truck

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CEE 427






Lane distribution factor (L) No. of lanes/direction

% of 18-kip ESAL in design lane

1

100

2

80 – 100

3

60 – 80

4

50 – 75

Total growth factor = (G)(Y) = [(1+r)Y – 1]/r r = annual growth rate


Pavement Design



Use total ESAL over analysis period if pavement d designed d ffor analysis l periodd without h any rehabilitation or resurfacing.



Use ESAL during any period for stage construction, rehabilitation,, resurfacingg

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CEE 427


Material Characterization 52

Pavement Design



Soil (subgrade) strength measured using MR



Layer coefficients for HMA, Base, and Subbase



Drainage coefficients

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CEE 427

Material Characterization Subgrade 53

 

Lab resilient modulus tests – AASHTO T307 Performed f d on representative samples in stress and moisture conditions simulating those of the primary moisture seasons.

Specimen size depends on the particle size

σd σc 6” σc

σc

12”

σc = confining pressure σd = cyclic deviator stress σ3 = σc σ1 = σd + σc σd = σ1 – σ3

CAB / SG

Compressed air

Material Characterization Subgrade 54

Mr = resilient modulus, psi Pa = normalizing stress (atmospheric pressure)  = bulk stress; sum of principle stresses oct = octahedral shear stress = 1  1   2 2   1   3 2   2   3 2 3

Pavement Design

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CEE 427

Material Characterization Subgrade – California Bearing Ratio (CBR) 55



Simple strength test that compares the b rin capacity bearing p it off a m material t ri l with ith th thatt of a well-graded crushed stone (AASHTO T193)



high quality crushed stone material should have CBR  100%



Developed by CA Division of Highways (1930) and was subsequently adopted by numerous states, counties, U.S. federal agencies and internationally.




Applying load to a small penetration piston at a rate of 0 05”/min & rrecording 0.05”/min rdin th the ttotal t l lload d att penetrations p n tr ti n rranging n in from 0.025 in. up to 0.300 in.  x CBR (%)  100   y  

Pavement Design

x = unit load on piston for 0.1” or 0.2” of penetration y = standard unit load for well-graded crushed stone - for 0.1" pen = 6.9 MPa (1000 psi) - for 0.2" pen= 10.3 MPa (1500 psi)

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CEE 427


General Soil Type

USC Soil Type

CBR Range

GW

40 - 80

GP

30 - 60

GM

20 - 60

GC

20 - 40

SW

20 - 40

SP

10 - 40

SM

10 - 40

Coarse-grained soils

SC

5 - 20

ML

15 or less

CL LL < 50%

15 or less

OL

5 or less

MH

10 or less

CH LL > 50%

15 or less

OH

5 or less

Fine-grained soils

Material Characterization Subgrade – Resistance Value (R-value) 58

Pavement Design



Measure of the material's resistance to plastic flow.



Lab prepared samples fabricated to a moisture & density condition representative of worst possible in-situ condition of a compacted SG.



R-value calculated from ratio of applied vertical pressure to p lateral p pressure. developed



testing apparatus: Stabilometer

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CEE 427

Material Characterization Subgrade – Resistance Value (R-value) 59

R  100 

  

100 2.5 / D 2 Pv / Ph  1  1

Pv = vertical pressure = 160 psi Ph = horizontal pressure at Pv of 160 psi D2 = displacement of stabilometer fluid necessary to increase horizontal pressure from 5 to 100 psi

CA Division of Highways D4” x H 4.5” sample

Material Characterization Subgrade Strength 60



MR can be estimated  if R-value is known MR = 145 × 10(0.0147R+1.23), psi Typical R-values: - well-graded (dense gradation) crushed stone base course: 80+ - MH silts: 15-30



Pavement Design

or CBR value is known MR = 2555×(CBR)0.64, psi

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CEE 427

Material Characterization – Layer Coefficients ai 61



A measure of relative ability of a unit thickness of a given layer to function as structural component of the pavement.



Determined from correlations with material properties: ai = f(MR)



NDOT:

aPlantmix Surface aRoadbed Modification aAggregate Base aBorrow

= 0.35 = 0.18 = 0.10 = 0.07

(E2 = 21200 psi)

Material Characterization – Drainage Coefficients mi 62



Account for loss of strength of pavement layers under moisture effects effects.



Drainage coefficients m2 and m3 applied to granular bases and subbases to modify the layer coefficients.



depends on:  Quality of drainage (time required to remove most of the water) 

Pavement Design

% of time pavement is exposed to moisture levels approaching saturation

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CEE 427




Quality of drainage rated by the time of standing water t or saturated t t d conditions diti


Pavement Design



Recommended m-values for untreated bases and subbases. bb



Ex: pavement designed with fair drainage (moisture drains within a week) and 2 months/year are likely to be saturated conditions: m2 = m3 = 0.8 - 1.0

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CEE 427


Reliability 66

Pavement Design



Probabilistic: Each design factor assigned a mean and a variance. variance



Reliability: defined as the probability that the design will perform its intended function over its design life.



Incorporates some degree of certainty into the design process to ensure that the various design alternatives will last the analysis period.

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CEE 427

Reliability 67



Overall standard deviation (S0): Takes into account error due to variabilityy in estimatingg traffic,, material strength g & construction practice (0.3 – 0.5).



S0 typically about 0.45 for flexible pavement.



ZR – probability that the serviceability will be maintained over the design life of the pavement. Or probability that pavement will ill perform f at or above b pt during d i the h ddesign i period i d (i (inverse off the standard normal cumulative distribution).



S0, ZR – used together to ensure the likelihood that the pavement performs at the expected level of R.

Reliability 68



Suggested Levels of Reliability (R) for Various Road F Functional i l Classifications Cl ifi i Recommended Level of Reliability Functional Classification

Urban

Rural

Interstate and Other Freeways Principal Arterials Collectors Local

85-99.9 80-99 80-95 50-80

80-99.9 75-95 75-95 50-80

NOTE: Results based on a survey of the AASHTO Pavement Design Task Force

Pavement Design

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CEE 427


AASHTO DESIGN PROCEDURE 70



All design factors linked together in one design equation

log10 (W18 )  Z R S o  9.36 log10 ( SN  1)  0.20 

 PSI  log10   2.7  1094 0.4  ( SN 1)5.19

 2.32 log10 ( M R )  8.07

  

Pavement Design

Used to estimate the SN Solved from a nomograph MR is for SG if SN considered for entire pavement structure, otherwise it is the MR of the supporting layer

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CEE 427


log10 (W18 )  Z R S o  9.36 log10 ( SN  1)  0.20 

 PSI  log10   2.7  1094 0.4  ( SN 1)5.19

 2.32 log10 ( M R )  8.07     

W18 = predicted traffic load in ESAL (18 kips loads) ZR = standard normal deviate for specified reliability R S0 = combined standard error of the traffic prediction and performance prediction (0.45 for flexible pavements) PSI = pi – pt = difference between initial and terminal serviceability index MR = resilient modulus (psi)

72

log10 (W18 )  Z R S o  9.36 log10 ( SN  1)  0.20 

 PSI  log10   2.7  1,094 ( SN 1)5.19

0.4 

 2.32 log10 ( M R )  8.07

Pavement Design

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CEE 427




Strength of pavement represented by a Structural Number (SN) function of layer thickness thickness, layer coefficient, & drainage coefficient.



Total pavement structural number: SN = aiDimj

ai = layer coefficient – pavement relative quality as a structural unit – related to MR mi = drainage coefficient SN = solved from equation or nomograph




Select a set of thicknesses so that provided SN = a1D1 + a2D2m2 + a3D3m3 > required SN (nomograph)

a1, a2, & a3 = layer coefficient for the surface, base, & subbase, respectively D1, D2, & D3 = thickness of surface, base, & subbase, respectively E1 a1 E2 a2 m2 E3 a3 m3 MR

Pavement Design

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CEE 427


Procedure 1. Using E2 as MR determine d SN1 requiredd to protect the h b base (nomograph)

D1* 

SN1 a1

D1* is rounded up to nearest 0.5 in. and a design value of the surface structure number SN1* is calculated from D1* by

SN1*  a1 D1*


Procedure 2 Using 2. U i E3 as MR determine d t r i SN2 required r ir d tto pr protect t t th the subbase (nomograph)

D2  *

SN 2  SN 1* a2 m2

D2* is i rounded d d up tto nearestt 0.5 0 5 in. i and d a ddesign i value l off the surface structure number SN2* is calculated from D2* by

SN 2*  D2*a2 m2

Pavement Design

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CEE 427


Procedure 3 Based on roadbed MR determine the total SN3 required 3. (nomograph)

D3  *

SN 3  SN *2 a3 m3

D3* is i rounded d d up p tto nearestt 0.5 0 5 in. i and d a ddesign i value l off the surface structure number SN3* is calculated from D3* by

SN 3*  D3*a3m3

AASHTO DESIGN EXAMPLE 78

o o o o o o o o o

Pavement Design

Design a pavement for a 6-lane (both direction) urban principal arterial Pavement structure: asphalt concrete and granular base. Subgrade R-value = 36 Design years, Y = 20 Two-Way Traffic ADT = 19,000 Annual growth rate (r) = 3% Truck percentage, T = 4% Truck factor, Tf = 0.745 ESAL/Truck It is estimated it will take a day for water to drain from the pavement & that the pavement will be saturated about 15% of the time

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CEE 427

Solution 79

  

Initial serviceability index pi = 4.2 Final serviceability index pt = 2.5 psi = pi – pt = 4.2 – 2.5 = 1.7 Functional classification

Terminal serviceability pt

Interstate

30 3.0

Principal arterials

2.5

Collectors/locals

2.0

Solution Traffic Characterization 80

 

Directional Distribution D = 0.5 Lane Distribution L = 0.70 No. of lanes in each direction 1 2 3 4

Pavement Design

Percentage of 18-kip ESAL in design lane 100 80 – 100 60 – 80 50 – 75

L = 70 %

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CEE 427

Solution Traffic Characterization 81



Total growth factor = (G)(Y) = [(1+r)Y – 1]/r = [(1+0.03) [(1+0 03)20 – 1]/0.03 1]/0 03 = 26.87



ESAL for Design Lane ESAL  ADT 0 T Tf G D L 365Y 

ESAL = (19000)(0.04)(0.745)(0.50)(0.70)(26.87)(365) = 1,943,589  2  106

Solution Material Characterization 82



 



Pavement Design

Subgrade MR = 145  10(0.0147R+1.23) (0 014736+1 23) = 8329 psii = 145  10(0.014736+1.23) aPlantmix Surface = 0.35 aAggregate Base = 0.10 equivalent to E2 = 21200 psi Drainage g coefficient: Time to drain is 1 day – characterized as Good. Pavement expected to be saturated about 15% of the time: m2= 1.0

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Solution – Drainage Coefficients mi 83



Quality of drainage rated by the time of standing water t or saturated t t d conditions diti

Solution – Drainage Coefficients mi 84



Pavement Design

Recommended m-values for untreated bases and subbases. bb

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CEE 427

Solution Reliability 85

 

R = 90% S0 = 0.45 0 45 (typical for flexible pavements) Recommended Level of Reliability Functional Classification

Urban

Rural

Interstate and Other Freeways

85-99.9

80-99.9

Principal Arterials

80-99

75-95

Collectors

80-95

75-95

Local

50-80

50-80

86

2.6 SN1 =?? R = 90% So = 0.45 W18 = 2  106 PSI = 1.7 MR = 21,200 psi (E2 of Base)

Pavement Design

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CEE 427

Solution 87



SN1 = 2.6

D1= SN1/a1 = 2.6/0.35 = 7.43 in. (Round up to the next 1/2 in.) D1* = 7.5 7 5 in. in SN1* = a1D1* = 0.35  7.5 = 2.625

88

SN2 =?? 3.7 R = 90% So = 0.45 W18 = 2  106 PSI = 1.7 MR = 8,329 psi (Roadbed)

Pavement Design

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CEE 427

Solution 89



SN2 = 3.7

D2= (SN2 – SN1*)/(a2m2) = (3.7 – 2.625)/(0.10  1.0) = 10.75 ((Round up p to nearest 1/2 in.))

D2* = 11 in.

SN2* = SN1* + a2m2D2* = 2.625 + 0.10  1.0  11 = 3.725  3.7 OK

Solution 90



The Pavement will consist of 7.5 inch of asphalt concrete t surface f andd 11.0 11 0 inch i h off granular l b base. Asphalt Concrete Crushed Aggregate Base - CAB

7.5 inch 11.0 inch

Subgrade

Pavement Design

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Solution 91



Instead of 7.5 inch of asphalt concrete surface a 5.0 inch of AC will be used used. What is the new granular base thickness needed to maintain the required total SN?



SN2 = 3.7 = a1D1’ + a2m2D2’ = 0.355 + 0.101.0D2’ D2’ = (3.7 (3 7 – 0.355)/(0.101.0) 0 355)/(0 101 0) = 19.5 19 5 inch However you need to be careful when reducing the AC layer thickness

Meadowood Mall Way 92

Pavement Design

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CEE 427






Ground water was encountered at depths ranging between 33.5-45 33 5 45 ft below existing e isting grade at the time of exploration in Dec 1998. At the time of exploration in August 2007, ground water was encountered at depths ranging between 14-21 ft below existing grade on the west side of the Meadowood Mall Way bridge site, and 27 ft on the east side.




Ground water elevations will vary depending on:  the

time of year of construction,

 winter

precipitation levels prior to construction, and

 irrigation

Pavement Design

practices of upslope areas.

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CEE 427






Changes in water level  changes in moisture content  Native Nati e cla clay soils will exhibit e hibit considerable shrink-swell potential. In most explorations, clays were generally moist to wet  if overlaying soils were removed the clay soils would tend to shrink if allowed to dry.






A non-woven geotextile can be placed below aggregate base layer. layer Function of geotextile: 



Separation, Reinforcement, Flirtation/drainage

Some Benefits Reduce stresses on SG and prevent penetration of fines i b into base aggregate.  Reduce disturbance of sensitive SG  Reduce thickness of granular base 

Pavement Design

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

Design of geotextile Nott responsible N ibl ffor geotextile t til design. d i  Recommend non-woven geotextile on top of SG for the designed pavement section. 

Materials Information 98

 

 

Pavement Design

Dense-Graded Plantmix Unit Weight: 1.957 ton/yd3 Aggregate Base Unit Weight (Includes 8% Moisture: 138.5 lb/ft3 Liquid Asphalt, Type MC-70NV Prime Coat: 0.28 gal/yd2 Emulsified Asphalt, Type SS-1h (Diluted) Tack Coat: 0.06 gal/yd l/ d2

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CEE 427

Typical Nevada Construction Costs 99

Pavement Design

Material

Units

Cost

Type 1 Class B Aggregate Base

Ton

$15.00

Asphalt Concrete Surface Course

Ton

$75.00

Emulsified Asphalt – Type SS-1h (Tack Coat) Ton

$350.00

Liquid Asphalt – MC-70NV (Prime Coat)

Ton

$500.00

Non-woven Geotextile

Yard2

$5.00

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pavement-design

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