TECHNICAL NOTE

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TECHNICAL NOTE TECH NOTE NO: TITLE: AUTHOR: CONTACT: DATE/REV:

5 "K-150" Considerations for RW 9-27 M. R Thompson Ph: (217)333-3930 Email: [email protected] University of Illinois, Dept of Civil & Environmental Engineering 1211 NCEL, MC-250, Urbana, IL 61801 10/27//04

The attached document was prepared as a component of the "Subgrade Support and Stabilization" project ofthe O'Hare Modernization Program (OMP) The document is submitted as an OMP deliverable.

."

Ilk-150" Considerations for RW 9-27

Prepared by Marshall R. Thompson, PhD, PE Professor Emeritus of Civil Engineering Department of Civil & Environmental Engineering University of llinois @ Urbana-Champaign

Submitted to BPC Airport Partners

September

1, 2004

'.

Introduction

A concretepavement design for

RW 9-27

has been proposed by

McQueen and Associates. McQueen's pavement analysis is based on a ~k" of 150 psi/inch. The proposed pavement section is:

* IS-inch PCCP * 6-inch Asphalt Treated Base (ATB) (E= 4,000 ksi} * 6-inch Asphalt Treated Permeable Base (ATPB) (Considered as P-209 aggregate material) * 12-inch Stabilized Subgrade NOTE: The Stabilized Subgrade was not considered ~contribute" to the pavement support.

to

The estimated ~life" (per LEDFAA-V1.3) of the McQueen pavement section is approximately thirty (30) years. McQueen's analyses indicates the FAA ~conventional design" (per FAA Advisory Circular 150/5320-6D) provides a similar design. Pavement

Support

* The pavement support for Subgrade"

layer

over

the

ORD RW 9-27 is a 12-inch compacted subgrade.

~Stabilized

* Note in attached Table 2-3 from FAA's 6D Circular, that the typical ~k"s for ML and CL soils are between 100 and 200 psi/inch.

* In attached Figure 16 (Approximate interrelationships of soil classifications and bearing values) from the Portland Cement Association's ~PCA Soil Primer," a CBR of three (3) is correlated with a ~k" of 100 psi/inch.

* 6D presents a procedure for considering an ~improved layer" over the ~unimproved subgrade." Figure 2-4 (attached) from 6D indicates that for an unimproved subgrade ~k" of 100 psi/inch, a 6-inch crushed aggregate subbase will improve the ~k" to 150 psi/inch.

2

.'

~

Consider:

* The ATPB material is ~better than" (shear strength and modulus) the 6D crushed aggregate subbase. Section 206-b-5 in Circular 6-D indicates: ~Stabilized Subbase. The determination of k value for stabilized layers is a difficult problem. It is recommended that the k value be estimated as follows. The thickness of the stabilized layer should be multiplied by a factor ranging from 1.2-1.6 to determine the equivalent thickness of well-graded crushed aggregate." Thus, the 6-inch ATPB has an ~equivalent thickness" of 7.2 to 9.6

inches.

* The contribution of the 12-inch "stabilized subgrade" layer is not considered as an improved layer in the 6D procedure. * However, the "stabilized subgrade" is considerably "better than" the unimproved subgrade. The stabilized subgrade will provide (relative to the unimproved subgrade) increased strength/modulus/rutting resistance properties and will have significantly improved moisture resistance. * Circular 6D (Section 207) indicates that subgrade stabilization will provide, a "stable working platform." The stabilized subgrade will enhance constructability and contribute to the maintenance of construction schedules.

It is concluded that the assigned "k" of 150 psi/inch utilized in McQueen's analyses is realistic/appropriate can be readily achieved in RW 9-27 construction.

3

and

" TABLE 2-3. Soil Characteristics Pertinent to Pavement Foundations

I):> c",

_I, ()'

1>1"),,.DivISions II) (2)

Om\'d and gravelly soils

I.eller

N.llle

(3) OW

(4)

01'

Ow\'cI nr III,I)' gravel. pnntly g.adcl!

GU

Gravel or sand)' gravel, n",fol'n.ly graded Silly grnvd '" silty '",lIly CHiVe!

(iM ('n"rsctlnl;lIc.' ,..il>

(ie SW $1' Salld and sandy snils

SU SM

SC MI. Low cnm pressihilily LL '" 50 Finegrnine" Soils IIigh compressibilil)' 1.1- > 50 I'cal nlld olher fibrous urg,"ic soil.

Gr.\'d or sandy gravel. well graded

CL

("I°y'ey gravd or dayey ..'lIdy g.nvel SU"" or gravelly sand. ",,,II graded SOlid or gravelly 53nd. poorly groded SOlid or gravelly sand, uniformly graded Silly son,l '" silly g,ovclly saud Clayey sand or clayey gravelly sand Silts, sandy silts. gravclly sills. or diatomaceous snil.

Volue as Found'iion When NOI Subjeel In Frost Action

Value as Base Direclly under Wearing Surface

(5) Excellenl

(6) Good

Good 10 exccllent

"oor 10 fair

Good

Poor

O.."d 10 excellcn'

F"i..lo gilllll

Good

Compressibililyand Exp.nsion (S) Ahnosl none

Orain.ge Charaelerislics (9) Exeellenl

None In very slighl

Allllnslnllne

Exeellenl

None 10very slight Slillhlln lIIedilll1l

Alnlosl none

Excellenl

Very slighl

I'air III I,ollt

Poor

Slighllo medilllll

Slighl

Oood

I'oor

Almost nOlle

Fair 10 gnod

Almost none.

Excellenl

Fair 10 good

Poor 10 nol soitablc Nol suitable

Almosl none

Excellenl

(roml

"nor

NOlie lu vc.y sliShl None to very slight None 10very slighl Slighl 10 high

Poor 10 praclicnlly illl,'CIViolls Excellelll

Ve.y slighl

':"ir 10pour

Fair 10 good

Nol suitable

Sligbl 10high

Slighlio medium

fair 10 good

Not suilable

Me,limn 10 very high

Fair 10 good

Nol suilable

Poor

Nol suitable

Poor

Nol sllil"ble

Polenlial Frost Action (1) None 10very slighl

Unit Dry Weighl (pel) (II) 125-140

(12) 60.80

SubGrnde Modnln. k (pel) (13) 300 or Inoro

Crawler-Iype lraclur. rubber-lired c