1、STD.AASHT0 SRCH GDPS-3 V2-ENGL 198b = Ob37804 0048397 541 II t- Supplement to the AASHTO Guide-For American Association of State Highway and Transportation Officials STD-AASHTO SRCH GDPS-3 VE-ENGL L78b E Ob3980Li 0048398 488 1 Supplement to the For American Association of State Highway and Transport
2、ation Officials O 1998 by the American Association of State Highwa and Transportation Officials. AIE Ri, Resewed. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without written permission of the publishers. ISBN 1-5605 1-078-1 STD.AASHT0 SRCH
3、GDPS-3 VE-ENGL L9b = Ub39804 0048400 7bb AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS EXECUTIVE COMMITTEE 1996-1997 VOTING MEMBERS Officers: PRESIDENT: Darre1 Rensink, Iowa VICE PRESIDENT: David Winstead, Maryland SECRETARY-TREASURER: Clyde E. Pyers, Maryland Regional Represent
4、atives: REGION I: Carlos I. Pesquera, Puerto Rico REGION II: Robert L. Robinson, Mississippi REGION III: Robert A. Welke, Michigan REGION IV: Marshall W. Moore, North Dakota NON-VOTING MEMBERS Immediate Past President: Wm G. Burnett, P.E., Texas Executive Director: Francis B. Francois, Washington, D
5、, C. iii STD.AASHT0 SRCH GDPS-3 V2-ENGL L78b Ob3780Li 0048403 AT2 AMERICAN ASSOCIATION OF STATE HIGHWAY AND TRANSPORTATION OFFICIALS JOINT TASK FORCE ON PAVEMENTS Ofsicers: CHAIRMAN: Gary Carver, Wyoming VICE CHAIRMAN: Robert L. Walters, Arkansas SECRETARY: Paul Teng, FHWA Regional Representatives:
6、Region 1 Connecticut New York Pennsylvania Port Authority of NY and NJ FHWA Region 2 Arkansas Kentucky Louisiana North Carolina Region 3 Missouri Ohio Wisconsin Region 4 Arizona California Colorado Texas Washington Wyoming Charles E. Dougan Wes Yang Danny Dawood Harry Schmer1 Paul Yeng Robert L. Wal
7、ters Gary Shqe J.B. Esnard, Jr. Thomas M. Heme, Jr. Jay F. Bledsoe Aric Morse Stephen F. Shober George Way Kevin Herritt Steve Horton Ken Fultz Linda Pierce F.M. (Rick) Harvey iv 1 STD.AASHT0 SRCH GDPS-3 V2-ENGL L78b D Ob37804 0048402 737 D Representing Transportation Research Board Amir N, Hanna St
8、anding Committee on Planning Fred Van Kirk Subcommittees on Construction and Maintenance Dean M. Testa Subcommittee on Materials Larry Engbrecht Standing Committee on Aviation Craig Smith V Preface The Joint Task Force on Pavements-composed of members from the Highway Subcommittee on Design, one mem
9、ber each from the Highway Subcommittees on Materials, Construction, and Maintenance, and one from the Standing Committee on Planning-has developed this Supplement to the AASHTO Guide for the Design of Pavement Structures. This Supplement includes alternative design procedures that can be used in pla
10、ce of or in conjunction with Part II, Section 3.2 “Rigid Pavement Design” and Section 3.3 “Rigid Pavement Joint Design.” The development of these alternative design procedures began with AASHTOs NCHRP Project 1-30. This project was to utilize new data available as a result of the LTPP database to in
11、corporate new data on loss-of-support for use in the design of rigid pavements and overlays and to improve the selection of k values. The document was then validated and revised under an FHWA contract and then finally developed into design procedures for use by AASHTO. These alternative design proce
12、dures and a “Rigid Pavement Design Example” are included herein for those who would like to make use of the LTPP data in rigid pavement design. This supplement has been ballotted and approved for publication by AASHTOs Standing Committee on Highways. Vi STD*AASHTO SRCH GDPS-3 V2-ENGL 178b Ob34804 00
13、48404 501 SUPPLEMENTAL VERSION OF THE AASHTO GUIDE, PART II, SECTION 3.2 RIGID PAVEMENT DESIGN FOR DESIGN SECTION 3.3 RIGID PAVEMENT JOINT DESIGN OF PAVEMENT STRUCTURES AND This supplement has been prepared as an alternate method for rigid pavement design, in the form of an addendum to the current A
14、ASHTO Guide. It contains the recommendations from NCHRP 1-30, modified based on the results of the verification study conducted using the LTPP database. 3.2 RIGID PAVEMENT DESIGN This section describes the design for Portland cement concrete pavements, including jointed plain (JPCP), jointed reinfor
15、ced (JRCP), and continuously reinforced (CRCP). As in the design for flexible pavements, it is assumed that these pavements will carry traffic levels in excess of 70,000 18-kip 80-lrN (rigid pavement) ESALs over the performance period. Examples of use of this rigid pavement design procedure are pres
16、ented at the end of this supplement. Design of Different Types of Concrete Pavement. The JPCP design concept is to provide a sufficient slab thickness and joint spacing to minimize the development of transverse cracking. The JRCP and CRCP design concepts provide sufficient slab thickness and reinfor
17、cement to hold very tight the transverse cracks that form so that aggregate interlock will be maintained. The thickness of the design model upon which this guide is based was developed and validated specifically for JPCP, for which joint spacing is one of the important required design inputs affecti
18、ng thermal curling stresses and, thus, transverse cracking. A proper selection of slab thickness and joint spacing is required to control the development of transverse cracking for a given chte, base, and subgrade. JRCP has much longer joint spacing and CRCP has no joints, and the transverse cracks
19、that eventually form in these types of pavements must be held tight by sufficient steel reinforcement. The use of this design method to determine an appropriate slab thickness for JRCP or CRCP requires the selection of an input “hypothetical“ joint spacing. Research using the LTPP database has shown
20、 that the following input values of joint spacing will result in reasonable design thicknesses using this design method. JPCP: Actual joint spacing, ft. JRCP: Actual joint spacing if less than 30 ft 9 m, or 30 ft maximum (use this value only to obtain slab design thickness). CRCP: 15 ft 4.6 m (use t
21、his hypothetical value only to obtain slab design thickness). 1 STD-AASHTO SRCH GDPS-3 V2-ENGL L7b b391i 001i8405 LiLiA M Load Transfer at Joints. The ABSHTO design procedure is based on the AASHO Road Test pavement performance algorithm that was extended to include additional design features. Inher
22、ent in the use of the AASHTO procedure is the use of dowels at transverse joints. Joint faulting was not a distress manifestation at the Road Test due to the adequacy of the dowel design. A faulting design check is provided for doweled joints to ensure that the dowels are sized properly. If a signif
23、icant faulting problem is expected, an increase in dowel diameter or other design change may be warranted. The non-doweled faulting check was developed using more recent measurements of fiel data. If the designer wishes to consider undoweled joints, a design check for faulting is provided. If the fa
24、ulting check indicates inadequate load transfer, design modifications such as the use of dowels or changes in base type, drainage, and joint spacing may be made. In addition, if the designer wishes to consider undoweled joints, a design check is also made for critical stresses due to axle loads appl
25、ied near the transverse joint, along with a negative thermal gradient, creating a corner loading situation that would lead to premature cracking. If this check shows a potential problem, design modifications such as the use of dowels, increased slab thickness, or changes in base type may be made. 3.
26、2.1 Develop Effective Modulus of Subgrade Reaction (k-Value) The modulus of subgrade reaction (k-value) is defined as that measured or estimated on top of the finished roadbed soil or embankment upon which the base course and/or concrete slab will eventually be constructed. The k-value represents th
27、e subgrade (and embankment, if present); it does not represent the base course. The base course is considered a structural layer of the pavement along with the concrete slab, and thus its thickness and modulus are important design inputs in determining the required slab thickness in Section 3.2.2. T
28、he k-Value input defined. The elastic k-value on tog of the subgrade or embankment is the required design input. The gross k-value incorporated in previous versions of the AASHTO Guide represents not only elastic deformation of the subgrade under a loading plate, but also substantial permanent defor
29、mation. Only the elastic component of this deformation is considered representative of the response of the subgrade to traffic loads on the pavement. The elastic k- value test was the main subgrade test conducted extensively at the AASHO Road Test. When the elastic k-value was used in structural ana
30、lysis of the AASHO Road Test pavements, it was found that slab stresses computed with a three-dimensional finite element model were approximately equal to those measured in the field under full-scale truck axle loadings at creep speed, providing further justification for use of the elastic k-value i
31、n the design. Steps in determining design k-value. The k-value input required for this design method is determined by the following steps, which are described in this section: 1. Select a subgrade k-value for each season, using any of the three following methods: (a) Correlations with soil type and
32、other soil properties or tests. (b) Deflection testing and backcalculation (most highly recommended). (c) Plate bearing tests. 2 STD.AASHT0 SRCH GDPS-3 V2-ENGL L78b M Ob39804 004840b 384 M 2. Determine a seasonally adjusted effective k-value. 3. Adjust the seasonal effective k-value for effects of a
33、 shallow rigid layer, if present, and/or an embankment above the natural subgrade. Note that the AASHTO design methodology requires the mean k-value, not the lowest value measured or some other conservative value. Note also that no additional adjustment to the k- value is applied for loss of support
34、. Substantial loss of support existed for many sections at the ABSHO Road Test, which led to increased slab cracking and loss of serviceability. Therefore, the performance data, upon which the AASHO Road Test performance model is based, already reflect the effect of considerable loss of support. Ste
35、p I. Select a Subgrade k-Value for Each Season. A season is defined as a period of time within a year, such as 3 months (Le., spring, summer, fall, winter). The number of seasons and the length of each season by which a year is characterized depend on the climate of the pavements location. There are
36、 several ways to measure or estimate the subgrade elastic k-value. Procedures are provided for three methods described below-correlation methods, backcalculation methods, and plate testing methods. Correlation Methods. Guidelines are presented for selecting an appropriate k-value based on soil class
37、ification, moisture level, density, California Bearing Ratio (CBR), or Dynamic Cone Penetrometer (DCP) data. The CBR may also be estimated fiom the R-value. These correlation methods are anticipated to be used routinely for design. The k-values obtained from soil type or tests correlation methods ma
38、y need to be adjusted for embankment above the subgrade or a shallow rigid layer beneath the subgrade. The k-values and correlations for cohesive soils (A4 through A-7). The bearing capacity of cohesive soils is strongly influenced by their degree of saturation (Sr, percent), which is a function of
39、water content (w, percent), dry density (y, lb/fl!), and specific gravity (GJ: Recommended k-values for each fine-grained soil type as a function of degree of saturation are shown in Figure 40. Each line represents the middle of a range of reasonable values for k. For any given soil type and degree
40、of saturation, the range of reasonable values is about f. 40 psi/in 1 1 kPdmm. A reasonable lower limit for k at 100 percent saturation is considered to be 25 psi/in 7 kPa/mm. Thus, for example, an A-6 soil might be expected to exhibit k-values between about 180 and 260 psi/in 49 and 70 kPa/mm at 50
41、 percent saturation, and k-values between about 25 and 85 psi/in 7 and 23 kPa/mm at 100 percent saturation. Two different types of materials can be classified as A-4: predominantly silty materials (at least 75 percent passing the #200 sieve, possibly organic), an8 mixtures of silt, sand, and gravel
42、(up to 64 percent retained on #200 sieve). The former may have a density between about 90 and 105 3 STD.AASHT0 SRCH GDPS-3 V2-ENGL 198b m Ob39804 0048407 2LO E lb/ 1442 and 1682 kg/m3, and a CBR between about 4 and 8. The latter may have a density between about 100 and 125 lb/ft3 11602 and 2002 kg/m
43、3, and a CBR between about 5 and 15. The line labeled A-4 in Figure 40 is more representative of the former group. If the material in question is A-4, but possesses the properties of the stronger subset of materials in the A-4 class, a higher k-value at any given degree of saturation (for example, a
44、long the line labeled A-7-6 in Figure 40) is appropriate. 250 225 200 175 150 l25 I00 75 50 25 O Line rrpraen8 middle of nnge of k- vrlw br soil ck Range U e 40 pi/in -.i .i. i j., . ;. . for ail ckusr Ud degrees of saturation. II. For A4 matariai: w A4 line if dry density 90 to 105 pcf and CBR 4 O
45、8 are A-6 i . , . 1 pcf = 16.018 kg/m3 lpsi/in = .271 kPa/mm i 1 I I 1 I t I 1 I 50 55 60 65 70 75 80 85 90 95 100 Degree of saturation, percent Figure 40. The k-value versus degree of saturation for cohesive soils. 4 STD-AASHTO SRCH GDPS-3 V2-ENGL L78b = Ob37804 0048408 157 Recommended k-value rang
46、es for fine-grained soils, along with typical ranges of dry density and CBR for each soil type, are summarized in Table 1 1. The k-values and correlations for cohesionless soils (A-1 and A-3). The bearing capacity of cohesionless materials is fairly insensitive to moisture variation and is predomina
47、ntly a function of their void ratio and overall stress state. Recommended k-value ranges for cohesionless soils, along with typical ranges of dry density and CBR for each soil type, are summarized in Table 1 1. The k-values and correlations for A-2 soils. Soils in the A-2 class are all granular mate
48、rials falling between A-1 and A-3. Although it is difficult to predict the behavior of such a wide variety of materials, the available data indicate that in terms of bearing capacity, A-2 materials behave similarly to cohesionless materials of comparable density. Recommended k- value ranges for A-2
49、soils, along with typical ranges of dry density and CBR for each soil type, are summarized in Table 1 1. Correlation of k-values to California Bearing Ratio. Figure 4 1 illustrates the approximate range of k-values that might be expected for a soil with a given California Bearing Ratio. Correlation of k-values to penetration rate by Dynamic Cone Penetrometer. Figure 42 illustrates the range of k-values that might be expected for a soil with a given penetration rate (inches per blow) measured with a Dynamic Cone Penetrometer. This is a rapid hand-held testing devi
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