Astm stp 1198 1994

STP 1198 Nondestructive Testing of Pavements and Backcalculation of Moduli: Second Volume Harold L Von Quintus, Albert J Bush, III, and Gilbert Y Baladi, Editors ASTM Publication Code Number (PCN) 04-011980-08 AsTM 1916 Race Street Philadelphia, PA 19103 Printed in the U.S.A Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Library of Congress Cataloging-in-Publication Data Nondestructive testing of pavements of backcalculation of moduli, Second volume/Harold L Von Quintus, Albert J Bush, III, and Gilbert Y Baladi, editors p cm - - (STP 1198) Contains papers presented at the symposium held in Atlanta, GA on 23-24 June 1993, sponsored by ASTM Committee D-18 on Soil and Rock and its Subcommittee D4 on Road Paving Materials "ASTM publication code number (PCN) 04-011980-08." Includes bibliographical references and index ISBN 0-8031-1865-1 Pavements Testing~ongresses Nondestructive testing -Congresses I Von Quintus, H L (Harold L.) IL Bush, A J (Albert Jasper) IlL Baladi, Gilbert Y., 1943IV ASTM Committee D18 on Soil and Rock Subcommittee D-4 on Road and Paving Materials V Series: ASTM special technical publication: 1198 TE250.N572 1994 625.8'028'7~c20 94-24308 CIP Copyright 1994 AMERICAN SOCIETY FOR TESTING AND MATERIALS, Philadelphia, PA All rights reserved This material may not be reproduced or copied, in whole or in part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of the publisher Photocopy Rights Authorization to photocopy items for internal or personal use, or the internal or personal use of specific clients, is granted by the AMERICAN SOCIETY FOR TESTING AND MATERIALS for users registered with the Copyright Clearance Center (CCC) Transactional Reporting Service, provided that the base fee of $2.50 per copy, plus $0.50 per page is paid directly to CCC, 222 ROSEWOOD DR., DANVERS, MA 01923 PHONE: (508) 750-8400 FAX: (508) 750-4744 For those organizations that have been granted a photocopy license by CCC, a separate system of payment has been arranged The fee code for users of the Transactional Reporting Service is 0-8031-1865-1 91 $2.50 + 50 Peer Review Policy Each paper published in this volume was evaluated by three peer reviewers The authors addressed all of the reviewers' comments to the satisfaction of both the technical editor(s) and the ASTM Committee on Publications To make technical information available as quickly as possible, the peer-reviewed papers in this publication were printed "camera-ready" as submitted by the authors The quality of the'papers in this publication reflects not only the obvious efforts of the authors and the technical editor(s), but also the work of these peer reviewers The ASTM Committee on Publications acknowledges with appreciation their dedication and contribution to time and effort on behalf of ASTM Printed in Ann Arbor, MI December1994 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Foreword This publication, Nondestructive Testing of Pavements and Backcalculation of Moduli (Second Volume), contains papers presented at the symposium of the same name held in Atlanta, GA on 23-24 June 1993 The symposium was sponsored by ASTM Committee DI8 on Soil and Rock and its Subcommittee D4 on Road and Paving Materials Albert J Bush, II1, of U.S Army Corps of Engineers in Vicksburg, MS, Harold L Von Quintus of Brent Rauhut Engineering in Austin, TX, and Gilbert Y Baladi of Michigan State University in East Lansing, MI presided as symposium chairmen and are the editors of the resulting publication Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Contents Overview ix ANALYTICAL MODELS AND TECHNIQUES A d v a n c e d Backcalculation Techniques -J UZAN S H R P ' s L a y e r Moduli Backcalculation Procedure -G RADA, C RICHTER, AND P JORDAHL 38 Methodology for Identifying M a t e r i a l Properties in P a v e m e n t s M o d e l e d as L a y e r e d Viscoelastic Half Spaces N STUBBS, V TORPUNURI, R LYTTON, AND A MAGNUSON 53 Backcalculation of P a v e m e n t L a y e r Moduli, Thicknesses, and Bedrock D e p t h Using a Modified Newton M e t h o d - - R HARRICHANDRAN,T, MAHWOOD, R, RAAD, AND G BALADI 68 I m p r o v e d M e t h o d s for A C / P C C P a v e m e n t Backcalculation and E v a l u a t i o n - - K HALL AND M DARTER 83 Concrete P a v e m e n t Backcalculation Using I L L I - B A C K - - A IOANNIDES 103 Dynamic Analysis of FWD Loading and P a v e m e n t R e s p o n s e Using a ThreeDimensional Dynamic Finite Element P r o g r a m - - s ZAGHLOUL,T WHITE, V DRNEVICH, AND B COREE 125 MEASUREMENTAND CALCULATIONTECHNIQUES IN THE FIELD AND LABORATORY Verification of P a v e m e n t Response M o d e l s - - a ULLIDTZ, J KRARUP, AND T WAHLMAN 143 Field Validation of a Methodology to Identify M a t e r i a l P r o p e r t i e s in P a v e m e n t s Modeled as Layered Viscoelastic Halfspaces -v s TORPUNUR, N STUBBS, R L LYTTON, AND A H MAGNUSON 159 C o m p a r i n g L a b o r a t o r y a n d Backcalculated L a y e r Moduli on I n s t r u m e n t e d P a v e m e n t Sections -T AKRAM,T SCULLION, AND R E SMITH V 170 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized In-Situ and Laboratory Characterization of Nonlinear Pavement Layer M o d u l i - 203 K P GEORGE AND W UDDIN A Pavement Evaluation Procedure Incorporating Material Non-Linearity-218 J R DE ALMEIDA, S F BROWN, AND N H THOM Effect of Material Stress Sensitivity on Backcalculated Moduli and Pavement Evaluation R N STUBSTAD, J P MAHONEY, AND N F COETZEE 233 PROBLEMS/ERRORS ASSOCIATED W I T H BACKCALCULATION METHODS AND DESIGN PARAMETERS Misleading Results from Nondestructive Testing A CASE S T U D Y - - J W HALL, JR., 251 AND P S MCCAFFREY, JR Stochastic Analysis of Errors in Remaining Life Due to Misestimation of Pavement Parameters in N D T - - K M VENNALAGANTI, C FERREGUT, AND S NAZARIAN 261 Interpretation of Dynamic Survey Measurement on Pavement with Treated Roadbase P LEPERT, AND P CAPRIOLI 277 Phase LAG Effects on Analysis of FWD Data P E SEBAALY,AND S HOLIKAq'TI 291 The Effect of Annular Load Distributions on the Backcalculated of Moduli of Asphalt Pavement Layers -J A CROVETTI,AND M Y SHAHIN 309 Effects of Pavement-Falling Weight Deflectomer Interaction on Measured Pavement Response -K M BODDAPATI,AND S NAZARIAN 326 N D T FOR OTHER PAVEMENT USES Radar for Pavement Thickness Evaluation K R MASER,T SCULLION, 343 W M K RODDIS, AND E FERNANDO A Comparison of Laboratory and Field Subgrade Moduli at the Minnesota Road Research Project D A VAN DEUSEN, C A LENNGREN, AND D E NEWCOMB 361 Detection of Multi-Course Pavement Layers by the SASW Method N GUCUNSrd 380 Strategies for Application of the Falling Weight Deflectomer to Evaluate Load Transfer Efficiency at Joints in Jointed Concrete Pavements o J JACKSON, 395 M R MURPHY, AND A WIMSATT Field Testing and Structural Evaluation of Selected Concrete Pavement Sections in Florida -c L WU, AND M TIA 404 Backcalculation of System Parameters for Jointed Rigid Pavements 440 D R HILTUNEN AND R ROQUE vi Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Evaluation of Support Conditions Under Jointed Concrete Pavement Slabs-J A CROVETTI AND M R T CROVETTI 455 Determination of Voids Under Rigid Pavements Using Impulse M e t h o d s NAZARIAN, S REDDY AND M, BAKER 473 Evaluation of NDT Equipment for Measuring Voids Under Concrete Pavements w UDDIN AND W R HUDSON 488 PROPOSED STANDARD GUIDE The Quest for a Standard Guide to NDT Backealculation R w MAY AND H L VON QUINTUS 505 Author Index 521 Subject Index 523 vii Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Overview In June 1988, the first International Symposium on Nondestructive Testing (NDT) of Pavements and Backcalculation of layer moduli was held Since then, another symposium on NDT and backcalculation of layer moduli was held in August of 1991 and was sponsored by the Transportation Research Board Both of these symposia were well attended, and showed that there was a strong interest within the transportation community in the area of NDT and the use of deflection data for evaluating and designing pavement structures Unfortunately, these two symposia also showed that the industry was divided regarding the adequacy and use of stateof-the-art evaluation procedures for determining structural capacity of pavement structures As a result of the first symposium in 1988, ASTM Subcommittees D18.10 and D04.39 have been extensively involved in the preparation of standardized procedures for NDT and the evaluation of deflection data Standardized procedures have been prepared and approved for collecting deflection data with different devices These are listed below for reference purposes: D 4602 D 4694 D 4695 Standard Guide for Nondestructive Testing of Pavements Using Cyclic Loading Dynamic Deflection Equipment Standard Test Method for Deflections with a Falling-Weight-Type Impulse Load Device Standard Guide for General Pavement Deflection Measurements The task of standardizing backcalculation procedures, however, has been more difficult, because of the diversity of opinions and procedures currently in use by the transportation industry The first draft of a standard guide for backcalculation of layer moduli from deflection measurements was balloted in 1986 The latest draft balloted in 1992 received numerous negative ballots that were found to be persuasive More recently, there have been numerous research projects completed by individual transportation agencies and as part of the Strategic Highway Research Program (SHRP) With these recent advancements and the need to develop concurrence within the transportation industry to develop a standardized evaluation procedure, Subcommittees D18.10 and D04.39 suggested to the Executive Committees that ASTM sponsor the second International Symposium on Nondestructive Testing of Pavements and Backcalculation of Moduli This Second International Symposium was held in Atlanta, Georgia in June, 1993 The attendance at this symposium exceeded 80, representing 12 different countries and 25 states in the United States An attendance list is included at the end of this publication The symposium was divided into four sessions (two sessions per day) and one panel workshop or discussion on issues related to standardization of backcalculation procedures The papers presented at this Second International Symposium focused in the area of backcalculation of layer moduli techniques and comparisons of material moduli as measured in the laboratory to values calculated from field deflection measurements Information from these papers and discussion were used to establish whether a backcalculation procedure could be standardized based upon the current state-of-the-art technology The format of the presentations was divided into four sessions followed by a panel discussion Each of the sessions were subdivided into two parts as follows: ix Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized SESSION 1DAnalytical Models and Techniques for Backcalculation of Layer Moduli (5 Papers) Chairman Dr Albert J Bush III, U.S Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS Part of Session 1: Recent Developments and Tools to be Used in the Future for Evaluating Pavements Based on Backcalculation Techniques (2 Papers) Keynote Speaker Dr Jacob Uzan, Professor, Israel Institute of Technology (Technion), Israel, "Advanced Backcalculation Techniques." Part of Session 1: Methods and Procedures Used for Backcalculation of Material and Pavement Properties (4 Papers) SESSION 2DMeasurement and Calculation Techniques in the Field and Laborator~ Chairman Mr Harold L Von Quintus, President, Brent Rauhut Engineering Inc., Austin, TX Part of Session 2: Verification of backcalculation techniques and comparisons of laboratory measured values with those calculated from field measurements or deflections (4 papers) Part of Session 2: Characterization of Pavement Materials and the Effects of Non Linearity on Backcalculation of Layer Moduli (4 papers) SESSION - - N D T for Pavement Structural Evaluation, Design and Rehabilitation Chairman Dr Albert J Bush III, U.S Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS Part of Session 3: Problems/errors associated with backcalculation methods in terms of pavement evaluation, and backcalculation of design parameters for concrete pavements (4 papers) Part of Session 3: Analysis of deflection measurements and effects of load distributions on pavement response (4 papers) SESSION -NDT for Other Pavement Uses: Use of the Results From NDT to Determine Layer Thickness, Joint Efficiency, and Void Detection (5 Papers) Chairman Dr Gilbert Y Baladi, Professor, Michigan State University, East Lansing, MI SESSION Panel Discussion on Backcalculation of Layer Moduli Chairman Dr Gilbert Y Baladi, Professor, Michigan State University, East Lansing, MI Discussion paper presented by Richard May, Asphalt Institute, Lexington, KY and Harold L Von Quintus, Brent Rauhut Engineering, Austin, TS entitled "The Quest for a Standard Guide to NDT Backcalculation" Panel participants: Dr Albert J Bush III., U.S Army of Engineers, Waterways Experiment Station, Vicksburg, MS Dr Jacob Uzan, Israel Institute of Technology (Technion), Israel; Richter, Federal Highway Administration, Turner Fairbanks, Washington, DC; Dr Ullditz, Technical University of Denmark, Denmark, and Luckanen, Braun Intertec, Minneapolis, MN Papers m this STP are presented on those topics in the four sessions listed previously These papers include examples of different backcalculation of layer moduli procedures, comparisons X Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized between laboratory measured and field calculated values, as well as, the more common examples on the use of deflection testing to evaluate pavement structures The papers published represent eight different countries, eleven different states, and thirteen different educational agencies It is the hope of the organizers of this symposium that the papers presented will provide the readers with much of the latest information in the areas of pavement evaluation using NDT techniques, and application of that data for use in pavement design One of the goals and objectives of this symposium was to determine if the industry could find a common ground to standardize a backcalculation procedure In specific, this was the focus of the panel discussion at the end of the symposium This panel discussion was preceded by a paper entitled "The Quest for a Standard Guide to NDT Backcalculation" (presented by Mr Richard May) and a presentation by Dr Albert Bush (Symposium Cochairman and D4.39 Subcommittee Chairman) entitled "Where We Go From Here." From the question and answers during the panel discussion, it was the general consensus that backcalculation of layer moduli from deflection measurements will definitely be used in the future for the rehabilitation design and evaluation of pavement structures The question however, is still: what is the reliability of these values? Specifically, it was the general consensus of the panel and attendees that the accuracy of backcalculated moduli is model dependent and unknown, as well as those values measured in the laboratory because there is a diversity of opinion on the simulation of field conditions in the laboratory For example, there is controversy within the industry on whether backcalculation procedures should be based on a dynamic or static analysis, and what values actually represent the "truth," both in the laboratory or from field measurements In summary, most participants, concurred that there needs to be a standard "baseline" of values from which to compare on a project, material, or pavement bases, and that one should not become paralyzed by the imperfection of the procedures More importantly, research must be merged into practice on a consistent basis and one way to accomplish this is through the standardization process As such, a procedure needs to be standardized and that procedure should concentrate on user oriented issues Thus, the editors, panel, as well as most symposium participants involved in these discussions, believe that some standardized procedure should be pursued to ensure that a common set of values can be compared The editors wish to thank all those who participated in this symposium and who contributed to this STP Special thanks are given to the authors, the reviewers of the papers, ASTM Committees D18 and D4 for sponsoring the symposium, and to the members of Subcommittees D18.10 and D04.39 for their valuable input and efforts Last but not least, the editors would like to express their deep appreciation to the ASTM staff for their assistance in preparing for this symposium and in its preparation The high professional quality of ASTM publications would not be possible without their dedicated and professional efforts Dr Albert J Bush III U.S Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS; symposium cochairman and coeditor Mr Harold L Von Quintus President, Brent Rauhut Engineering, Austin, Texas, symposium cochairman and editor Dr Gilbert Y Baladi Professor of Civil Engineering, Michigan State University, East Lansing, Michigan, symposium cochairman and coeditor Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 512 NONDESTRUCTIVE TESTING: SECOND VOLUME above, u n l e s s c o r r e l a t i o n s are d e v e l o p e d and verified R e g r e s s i o n equations or s i m p l i f i e d a l g o r i t h m s d e v e l o p e d from q u a s i - s t a t i c l a y e r e d elastic model c o m p u t e r - g e n e r a t e d o u t p u t may be used, p r o v i d e d the r e s u l t i n g equivalent layer elastic m o d u l i are used to recalculate, in the layered elastic model, the d e f l e c t i o n s at each point u s e d w i t h i n the m e a s u r e d d e f l e c t i o n basin The p e r c e n t error (between c a l c u l a t e d and m e a s u r e d d e f l e c t i o n basins) s h o u l d then meet the same r e q u i r e m e n t s as d i s c u s s e d later PROCEDURE The f o l l o w i n g d i s c u s s i o n provides g e n e r a l g u i d e l i n e s intended to assist in the e s t i m a t i o n of the structural layer moduli of existing pavements Deflection Testinq The A S T M S t a n d a r d Guide for N o n d e s t r u c t i v e T e s t i n g of Pavements U s i n g Cyclic L o a d i n g D y n a m i c D e f l e c t i o n Equipment (D 4602) and ASTM S t a n d a r d Test M e t h o d for D e f l e c t i o n s w i t h a F a l l i n g - W e i g h t - T y p e Impulse L o a d D e v i c e (D 4694) p r o v i d e p r o c e d u r e s that can be u s e d for n o n d e s t r u c t i v e d e f l e c t i o n t e s t i n g of p a v e m e n t s using d y n a m i c cyclic and impact l o a d i n g d e f l e c t i o n equipment, r e s p e c t i v e l y These test p r o c e d u r e s g e n e r a l l y refer to the c a l i b r a t i o n and operation of v a r i o u s types of NDT equipment It should be e m p h a s i z e d that proper c a l i b r a t i o n of the sensors is essential for m e a s u r i n g accurate pavement responses, e s p e c i a l l y those far a w a y from the load The location and spacing of m e a s u r e m e n t s are r e c o m m e n d e d in A S T M Standard Guide for G e n e r a l Pavement D e f l e c t i o n M e a s u r e m e n t s (D 4695) Delineatinq Pavement Sections Plots of d e f l e c t i o n p a r a m e t e r s as a f u n c t i o n of l o n g i t u d i n a l d i s t a n c e or s t a t i o n can be v e r y helpful in d e f i n i n g p a v e m e n t s u b s e c t i o n s w i t h similar characteristics Longitudinal profile graphs of b o t h m a x i m u m surface d e f l e c t i o n and the d e f l e c t i o n m e a s u r e m e n t furthest from the load should be p r e p a r e d for the pavement b e i n g evaluated If the a p p l i e d load inducing these d e f l e c t i o n s v a r i e d by more than five percent, the i n d i v i d u a l d e f l e c t i o n s (especially the maximum) s h o u l d be n o r m a l i z e d to a reference load m a g n i t u d e to lessen the scatter in the data: normalized deflection = actual deflection r e f e r e n c e load x actual load Other d e f l e c t i o n b a s i n parameters, such as AREA, m a y also be p l o t t e d to p r o v i d e an i n d i c a t i o n of the v a r i a t i o n in overall load d i s t r i b u t i o n c a p a c i t y of the pavement However, the above normalization p r o c e s s is not n e c e s s a r y or a p p r o p r i a t e for the A R E A calculation A general formula for A R E A is d e f i n e d as follows for more than one d e f l e c t i o n sensor (other d e f i n i t i o n s exist for specific numbers of sensors, such as shown in Fig (Hoffman and Thompson, 1982)); r e s u l t s from d i f f e r e n t equations m a y not be comparable): n-i AREA=(Dist~/2)+[E 61 x i=2 where, (Dist i + Disti+,)/(2~max)]+[Dist, x ~n /(26max)] n is the number of sensors u s e d to m e a s u r e basin, Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorize 300 mm AREA D1/DO 300 mm 300 mm D3/DO CopyrightbyASTMInt'l(allrightsreserved);SunDec2714:44:10EST2015 Downloaded/printedby UniversityofWashington(UniversityofWashington)pursuanttoLicenseAgreement.Nofurtherreproductionsauthorized Fig Concept of "AREA" for Structural Capacity A R E A (mm) = 150 [1 + (D1/DO) + (D2/DO) + (D3/DO)] DO/DO = I 150 m m Ol _.L Z C r> > W > 0 Z Z U I C Z -I C < o Z > -< > 514 NONDESTRUCTIVE TESTING: SECOND VOLUME ~i is the d e f l e c t i o n m e a s u r e d w i t h s e n s o r i, Dist is the distance b e t w e e n sensor and i, Dist~ is the distance b e t w e e n sensor n and n-l, Dist, is the d i s t a n c e b e t w e e n sensor i and i-l, Dist~.~ is the distance b e t w e e n s e n s o r i and i+l, and ~max is the m a x i m u m d e f l e c t i o n at the center of the load, m e a s u r e d with sensor i By e v a l u a t i n g these and other l o n g i t u d i n a l profiles, p a v e m e n t segments w i t h s i g n i f i c a n t l y d i f f e r e n t p a v e m e n t r e s p o n s e c h a r a c t e r i s t i c s can be v i s u a l l y and/or s t a t i s t i c a l l y d e s i g n a t e d as individual subsections Note 3: For some o v e r l a y d e s i g n procedures, results from d e f l e c t i o n t e s t i n g are i n i t i a l l y u s e d to d e s i g n a t e d e s i g n sections and aid in e v a l u a t i n g d i f f e r e n c e s in m a t e r i a l properties D e f l e c t i o n data are p l o t t e d in the form of a p r o f i l e by l o c a t i o n t h r o u g h o u t the length of the p a v e m e n t s e c t i o n and then s e p a r a t e d into subsections with s i m i l a r d e f l e c t i o n b a s i n characteristics In other p r o c e d u r e s , layer moduli are i n i t i a l l y c a l c u l a t e d for each m e a s u r e d b a s i n and t h e n these moduli or the e x p e c t e d p a v e m e n t p e r f o r m a n c e b a s e d on these m o d u l i are u s e d to d e l i n e a t e u n i f o r m subsections Note 4: S u b s e c t i o n s with similar deflections, d e f l e c t i o n b a s i n characteristics, moduli, a n d / o r e x p e c t e d p a v e m e n t p e r f o r m a n c e can be s t a t i s t i c a l l y c h e c k e d by u s i n g the Student-t test to d e t e r m i n e if two sets of data are s i g n i f i c a n t l y different U n d e r v a r i a b l e t o p o g r a p h i c a l or g e o l o g i c a l conditions, b a c k c a l c u l a t i o n of layer moduli for each m e a s u r e m e n t location may be p r e f e r r e d or even necessary In more u n i f o r m situations, for s i m p l i f i c a t i o n purposes, an actual "representative" d e f l e c t i o n basin could be s e l e c t e d for analysis However, some s i t e - s p e c i f i c i n f o r m a t i o n can be m i s s e d and/or a d d i t i o n a l error introduced Basins with large d i f f e r e n c e s (greater than two s t a n d a r d d e v i a t i o n s within the d e s i g n section) that may occur could be o v e r l o o k e d by a n a l y z i n g o n l y a "representative" basin Locations with notably different d e f l e c t i o n m a g n i t u d e s should be e v a l u a t e d individually Note 5: If the pavement exhibits o n l y o c c a s i o n a l cracks, such as asphalt thermal c r a c k i n g or concrete joints or cracks, the d e f l e c t i o n b a s i n s s e l e c t e d for analysis should represent u n c r a c k e d surfaces (or m e a s u r e m e n t s should be taken w i t h the load and all s e n s o r s at least 1.5 m (5 ft) f r o m any cracks), b e c a u s e layered elastic t h e o r y does not c o n s i d e r these discontinuities If the p a v e m e n t surface has e x t e n s i v e cracking, then these areas should be e v a l u a t e d as well and the type and s e v e r i t y of cracks should be noted on the report with the b a c k c a l c u l a t e d layer elastic moduli These kinds of n o t a t i o n s m a y be h e l p f u l in e x p l a i n i n g the analysis findings for that location The c a l c u l a t e d e q u i v a l e n t moduli will u s u a l l y reflect the surface condition A p p r o x i m a t e m a t e r i a l c l a s s i f i c a t i o n s and layer t h i c k n e s s e s can be o b t a i n e d from h i s t o r i c a l as-built c o n s t r u c t i o n records A p a v e m e n t c o r i n g p r o g r a m will p r o v i d e more a c c u r a t e thicknesses, p r e f e r a b l y to the n e a r e s t m m (0.2 in.) for b o u n d layers or 25 mm (i.0 in.) for u n b o u n d layers, and the material type of each layer in the pavement structure, and also check for the e x i s t e n c e of a shallow rigid layer (e.g bedrock) Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authori MAY AND VonQUINTUS ON NDT BACKCALCULATION Note 515 6: As a general rule, all m a t e r i a l types and layer t h i c k n e s s e s r e c o v e r e d from as-built c o n s t r u c t i o n plans should be v e r i f i e d u s i n g field cores and/or b o r i n g s if at all possible The n u m b e r of cores r e q u i r e d per analysis s e c t i o n or project is not a part of this standard E n g i n e e r i n g j u d g e m e n t may be n e e d e d or s t a t i s t i c a l m e t h o d s m a y be u t i l i z e d (Yoder and Witczak, 1975) to d e t e r m i n e the n u m b e r of cores r e q u i r e d to estimate layer t h i c k n e s s e s to a d e s i r e d level of p r e c i s i o n and d e g r e e of confidence T h i c k n e s s v a r i a t i o n s are d e p e n d e n t on c o n s t r u c t i o n p r a c t i c e and m a i n t e n a n c e activities However, it should be n o t e d that any d e v i a t i o n b e t w e e n the a s s u m e d and actual in-place layer t h i c k n e s s e s may affect the b a c k c a l c u l a t e d layer moduli significantly For each individual m e a s u r e d or the "representative" m e a s u r e d d e f l e c t i o n b a s i n to be evaluated, the r e q u i r e d data are e n t e r e d into the p r e f e r r e d a n a l y t i c a l technique The N D T device l o a d i n g c h a r a c t e r i s t i c s , Poisson's ratios and t h i c k n e s s e s of all the assumed individual layers, d e f l e c t i o n values and locations, and p o s s i b l y initial e s t i m a t e s of the layer moduli (seed moduli) are i n c l u d e d in the input data set The Poisson's ratio of the subgrade should be s e l e c t e d carefully Small v a r i a t i o n s in this value m a y cause s i g n i f i c a n t d i f f e r e n c e s in the moduli of the upper p a v e m e n t layers Typical ranges of Poisson's ratio values, that m a y be u s e d if other values are not available, are the following: asphalt c o n c r e t e : p o r t l a n d cement c o n c r e t e : u n b o u n d granular bases : c o h e s i v e soil : c e m e n t - s t a b i l i z e d soil : l i m e - s t a b i l i z e d soil : ' Depending Note 0.30 0.10 0.20 0.25 0.10 0.10 on strain level and degree to to to to to to 0.40 0.20 0.40' 0.45" 0.30 0.30 of saturation 7: In programs where seed m o d u l i are required, their s e l e c t i o n can affect the number of n e c e s s a r y iterations, the time r e q u i r e d b e f o r e an a c c e p t a b l e solution is a c h i e v e d and possibly, the final moduli that are determined If an e x t r e m e l y p o o r selection of moduli is made, the analysis m a y p o s s i b l y fail to find a solution w i t h i n the s p e c i f i e d t o l e r a n c e b e t w e e n c a l c u l a t e d and m e a s u r e d deflections In this case, an a l t e r n a t e set of seed m o d u l i m a y p r o v i d e an a c c e p t a b l e s o l u t i o n b e f o r e r e a c h i n g the m a x i m u m a l l o w a b l e n u m b e r of iterations Ordinarily, if the tolerance is s u f f i c i e n t l y narrow, the final moduli that are c a l c u l a t e d are not s i g n i f i c a n t l y a f f e c t e d by the values c h o s e n for the initial set of seed moduli In addition, m a n y programs require a range of a c c e p t a b l e moduli values for each of the layers to improve the speed of o p e r a t i o n and to limit the m o d u l i to their a p p r o x i m a t e p r a c t i c a l values Thin Layers in Pavements For u p p e r surface layers that are thin, that is, less than 1/4 of the d i a m e t e r of the loaded area (for example, 75 mm (3 in.) or less for a 300 mm (12 in.) loading plate) or layers that are thinner than the layer d i r e c t l y above, the elastic moduli often cannot be a c c u r a t e l y d e t e r m i n e d by most b a c k c a l c u l a t i o n methods These thin layers, if possible, should be c o m b i n e d in a s s i g n e d t h i c k n e s s with Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authori 516 NONDESTRUCTIVE TESTING: SECOND VOLUME the same type of m a t e r i a l above or b e l o w the thin layer, or the moduli of the thin layers can be e s t i m a t e d and a s s i g n e d as "known" values For thin asphalt concrete layers (with v e r y few cracks) on u n b o u n d g r a n u l a r base courses, the e l a s t i c moduli m a y be m e a s u r e d in the l a b o r a t o r y u s i n g A S T M S t a n d a r d Test M e t h o d for Indirect T e n s i o n Test for R e s i l i e n t M o d u l u s of B i t u m i n o u s M i x t u r e s (D 4123), or m a t h e m a t i c a l l y e s t i m a t e d u s i n g a v a i l a b l e r e g r e s s i o n equations (Asphalt Institute, 1982) or n o m o g r a p h s (Shell International, 1978) The t e m p e r a t u r e at which the modulus is m e a s u r e d or e s t i m a t e d should c o r r e s p o n d to that w h i c h e x i s t e d in the field at the time the d e f l e c t i o n s were measured For flexible p a v e m e n t s w i t h single or double b i t u m i n o u s s u r f a c e treatments, the surface layer is u s u a l l y c o m b i n e d w i t h the base material in the b a c k c a l c u l a t i o n procedure L u m b e r of Layers B a s e d on r e c o m m e n d e d practice, the number of u n k n o w n layers (including subgrade but e x c l u d i n g any fixed a p p a r e n t stiff layer) to be b a c k c a l c u l a t e d s h o u l d be no more than five and p r e f e r a b l y less In order to solve for a number of "unknowns" (for example, four layer moduli), as a minimum, that same n u m b e r and more, if available, of "knowns" (for example, five deflections) should be provided, to b e t t e r d e f i n e the b a s i n and reduce the number of p o s s i b l e c o m b i n a t i o n s of moduli that would p r o v i d e a d e f l e c t i o n b a s i n match A l t h o u g h m o r e d e f l e c t i o n points can be d e r i v e d a r t i f i c i a l l y by i n t e r p o l a t i n g b e t w e e n actual m e a s u r e d points, this is not r e c o m m e n d e d b e c a u s e a d d i t i o n a l error can be i n t r o d u c e d by not i n t e r p r e t i n g the correct changes in slope b e t w e e n points Therefore, if four d e f l e c t i o n sensors were used, then a m a x i m u m of four u n k n o w n layers (three p a v e m e n t layers and the subgrade) could be u s e d in the s t r u c t u r a l evaluation For a p a v e m e n t where more than three to five layers were constructed, the t h i c k n e s s e s of layers of similar (same type of binder) m a t e r i a l s may be c o m b i n e d into one e f f e c t i v e s t r u c t u r a l layer for b a c k c a l c u l a t i o n purposes T h e s e analysis techniques, in general, i t e r a t i v e l y p r o g r e s s toward the center of the d e f l e c t i o n b a s i n from the outer edge of the b a s i n in d e t e r m i n i n g these layer moduli For example, it is possible to estimate (AASHTO, 1986) the m i n i m u m d i s t a n c e from the c e n t e r of the a p p l i e d load at w h i c h the d e f l e c t i o n m e a s u r e d at the pavement surface is due p r i m a r i l y to the strain or d e f l e c t i o n of the subgrade (see Fig i), r e l a t i v e l y independent of the o v e r l y i n g layers Therefore, a m e a s u r e d d e f l e c t i o n b e y o n d this d i s t a n c e can be used to solve for the e f f e c t i v e subgrade m o d u l u s at that stress level directly For s t r e s s - d e p e n d e n t materials, it is a d v i s a b l e that the first sensor b e y o n d this distance be u s e d to solve for the subgrade modulus D e p e n d i n g on the materials in the p a v e m e n t structure, it may be n e c e s s a r y to e m p l o y n o n - l i n e a r response p a r a m e t e r s in the process Each s u c c e e d i n g d e f l e c t i o n point can be a t t r i b u t e d to strains that occur in response to the load in s u c c e s s i v e l y more layers and it t h e r e f o r e provides some a d d i t i o n a l "known" i n f o r m a t i o n about the u p p e r p a v e m e n t layers The e f f e c t i v e m o d u l i of these upper layers are then e s t i m a t e d using the closer (to the load) deflections and the p r e v i o u s l y e s t i m a t e d lower layer moduli Estimation of an A p p a r e n t Stiff Layer M a n y b a c k c a l c u l a t i o n p r o c e d u r e s include an a p p a r e n t stiff (Mr = 700 to 7000 MPa (100,000 to 1,000,000 psi)) layer at some depth into the subgrade It is intended to s i m u l a t e either b e d r o c k or the depth where it appears that v e r t i c a l d e f l e c t i o n is negligible Research has shown that the results of the analysis can be s i g n i f i c a n t l y i n a c c u r a t e by not i n c l u d i n g such a layer or by not l o c a t i n g this stiff layer near the actual depth, p a r t i c u l a r l y if the actual depth is less t h a n 4.6 m (15 ft) The m a g n i t u d e of this e r r o r is also Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions author MAY AND VonQUINTUS ON NDT BACKCALCULATION 517 a f f e c t e d b y the m o d e l i n g of the subgrade; for example, a n o n l i n e a r s t r e s s - d e p e n d e n t (softening) m a t e r i a l w o u l d also lead to "stiffer" s u b g r a d e layers w i t h depth, or d e c r e a s i n g stress, if i n c l u d e d in the t o t a l n u m b e r of layers T o l e r a n c e s of D e f l e c t i o n M a t c h i n q The a c c u r a c y of the final b a c k c a l c u l a t e d m o d u l i is a f f e c t e d b y the t o l e r a n c e a l l o w e d w i t h i n the p r o c e d u r e for d e t e r m i n i n g a m a t c h b e t w e e n the c a l c u l a t e d and m e a s u r e d d e f l e c t i o n s Two different a p p r o a c h e s are c o m m o n l y e m p l o y e d for e v a l u a t i n g this "match" These are an a r i t h m e t i c a b s o l u t e sum (AASE) of p e r c e n t e r r o r and a root m e a n s q u a r e (RMSE) p e r c e n t error In b o t h p r o c e d u r e s , the e n g i n e e r s h o u l d b e a r in m i n d that the s i g n i f i c a n c e of r a n d o m s e n s o r e r r o r can b e m u c h g r e a t e r at the o u t e r s e n s o r l o c a t i o n s w h e r e the a c t u a l m e a s u r e d d e f l e c t i o n s are v e r y small; therefore, d i f f e r e n t t o l e r a n c e w e i g h t i n g f a c t o r s for e a c h s e n s o r m a y be a c o n s i d e r a t i o n A n a r i t h m e t i c a b s o l u t e sum of p e r c e n t error, AASE, m a y be u s e d to e v a l u a t e the m a t c h b e t w e e n the c a l c u l a t e d and m e a s u r e d d e f l e c t i o n b a s i n s a n d is d e f i n e d as: n A A S E = i00 E I (@measl - 6calcl)/ 6measll i=l where n : n u m b e r of s e n s o r s u s e d to m e a s u r e basin, ~meas i = m e a s u r e d d e f l e c t i o n at p o i n t i, a n d ~calc i = c a l c u l a t e d d e f l e c t i o n at p o i n t i The m a g n i t u d e of t o l e r a n c e v a r i e s w i t h the n u m b e r of d e f l e c t i o n s e n s o r s u s e d to d e f i n e the basin It is s u g g e s t e d that the sum of p e r c e n t e r r o r s h o u l d not be g r e a t e r t h a n the f o l l o w i n g v a l u e s for the p a v e m e n t s e c t i o n to be a d e q u a t e l y c h a r a c t e r i z e d : 9-18 p e r c e n t 7-14 p e r c e n t 5-10 p e r c e n t if n i n e d e f l e c t i o n s e n s o r s are used, if s e v e n d e f l e c t i o n s e n s o r s are used, if five d e f l e c t i o n s e n s o r s are used and N o less t h a n five d e f l e c t i o n s e n s o r s s h o u l d be u s e d to d e s c r i b e the basin A root m e a n s q u a r e p e r c e n t error, RMSE, m a y a l s o be u s e d to e v a l u a t e the m a t c h b e t w e e n the c a l c u l a t e d and m e a s u r e d d e f l e c t i o n basins This m e a s u r e of e r r o r is less d e p e n d e n t o n the n u m b e r of s e n s o r s u s e d to characterize the d e f l e c t i o n basin However, the same m i n i m a l n u m b e r of d e f l e c t i o n s e n s o r s (five) as a b o v e s h o u l d be followed R M S E is d e f i n e d as follows: R M S E = i00 n {i/n E [(~calcl - ~measl)/ 6measl] }0.5 i=1 w h e r e the p a r a m e t e r s are the same as p r e v i o u s l y d e f i n e d A maximum t o l e r a n c e limit of to p e r c e n t o n the root m e a n s q u a r e e r r o r is recommended N o t e 8: If the above r e q u i r e m e n t s for the p e r c e n t e r r o r cannot be met, t h e n c o n d i t i o n s m a y exist w h i c h v i o l a t e the a s s u m p t i o n s of l a y e r e d e l a s t i c t h e o r y or the a c t u a l layer c o m p o s i t i o n s or t h i c k n e s s e s m a y be s i g n i f i c a n t l y d i f f e r e n t t h a n t h o s e u s e d in the model A d d i t i o n a l f i e l d m a t e r i a l s a m p l i n g or c o r i n g at t h e s e l o c a t i o n s m a y p r o v i d e the m e a n s to r e s o l v e this problem If this c o n d i t i o n c a n n o t be reconciled, t h e n m o r e c o m p l e x m o d e l s w h i c h c a n s i m u l a t e d y n a m i c loading, m a t e r i a l i n h o m o g e n e i t i e s , Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions 518 NONDESTRUCTIVE TESTING: SECOND VOLUME or p h y s i c a l be used Note CONTENTS 9: discontinuities in the p a v e m e n t should There are several factors that affect the a c c u r a c y and a p p l i c a b i l i t y of b a c k c a l c u l a t e d layer moduli A n y analysis method that uses an i t e r a t i v e or s e a r c h i n g p r o c e d u r e to m a t c h m e a s u r e d to c a l c u l a t e d d e f l e c t i o n basins will result in some error The m a g n i t u d e of this error depends on d i f f e r e n t factors, some of which include: (i) c o m b i n i n g d i f f e r e n t layers into one s t r u c t u r a l layer, (2) n u m b e r of d e f l e c t i o n p o i n t s and l i m i t a t i o n on number of layers u s e d in the analysis, (3) "noise" or inaccuracies c o n t a i n e d in the sensor m e a s u r e m e n t itself; small d e f l e c t i o n s that are c l o s e in m a g n i t u d e to the e s t a b l i s h e d r a n d o m error for the sensors, (4) d i s c o n t i n u i t i e s such as c r a c k s in the pavement, p a r t i c u l a r l y if located b e t w e e n the load and the sensor, (5) i n a c c u r a t e a s s u m p t i o n of the e x i s t e n c e and depth of an apparent stiff layer; depths less than feet m a y require a d y n a m i c analysis, (6) d i f f e r e n c e s b e t w e e n a s s u m e d and actual layer thicknesses; due to i n a c c u r a t e or u n a v a i l a b l e m e a s u r e m e n t s or p o i n t - t o - p o i n t v a r i a b i l i t y , (7) s a t u r a t e d clays d i r e c t l y b e n e a t h b a s e materials, (8) e x t r e m e l y weak soils b e n e a t h the b a s e and o v e r l y i n g m u c h s t i f f e r soils, (9) n o n - u n i f o r m load p r e s s u r e d i s t r i b u t i o n s at the l o a d - p a v e m e n t c o n t a c t area, (I0) non-linear, inhomogeneous, or a n i s o t r o p i c m a t e r i a l s in the pavement structure (especially the subgrade) and (II) for s u c c e s s i v e layers, a stiffness ratio (Mr upper layer/ M, lower layer) less then 0.3 OF REPORT The report d o c u m e n t i n g the b a c k c a l c u l a t e d layer m o d u l i for each p a v e m e n t s e c t i o n s h o u l d include the following: results i) Identification~location of p a v e m e n t tested, l o c a t i o n of test points analyzed, date and time of d e f l e c t i o n testing, file name of original d a t a file, and the b a c k c a l c u l a t i o n p r o g r a m (including v e r s i o n number) used 2) D e t a i l s of the N D T device (load range, s p a c i n g of all d e f l e c t i o n sensors) load footprint, and 3) The thicknesses, Poisson's ratios (assumed or measured) and material types of each layer in the p a v e m e n t s t r u c t u r e t h r o u g h o u t the test s e c t i o n as well as the source of this information Any d i f f e r e n c e s in c o n s t r u c t i o n h i s t o r y or p a v e m e n t c r o s s - s e c t i o n within the s e c t i o n should be n o t e d if the i n f o r m a t i o n is k n o w n or available In addition, any layers that were c o m b i n e d into one s t r u c t u r a l layer for analysis should be so indicated 4) V i s u a l c h a r a c t e r i s t i c s of the test section T h e s e could include n o t a t i o n s on the location of changes in p a v e m e n t features such as surface a p p e a r a n c e or type, t r a n s i t i o n s from cut to fill, p r e s e n c e of culverts, d i f f e r e n t soil types, and d i f f e r e n t shoulder widths In addition, the locations, types, severity, and extent of p a v e m e n t d i s t r e s s e s such as rutting, washboarding, b l o c k cracking, and fatigue c r a c k i n g s h o u l d be noted to aid the e n g i n e e r in u n d e r s t a n d i n g any a n o m a l i e s in the data The location of the applied Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions autho MAY AND VonQUINTUS ON NDT BACKCALCULATION loading relative to any n e a r b y surface distress 519 should also be noted 5) The ambient air t e m p e r a t u r e and p a v e m e n t surface t e m p e r a t u r e for each b a s i n m e a s u r e m e n t In addition, the a v e r a g e a s p h a l t p a v e m e n t layer t e m p e r a t u r e can be o b t a i n e d by d r i l l i n g a small hole to the m i d d e p t h of the asphalt concrete, f i l l i n g with l i q u i d (oil or water), and m e a s u r i n g the liquid t e m p e r a t u r e w i t h a t h e r m o m e t e r set in the fluid after the r e a d i n g has stabilized If this is not possible, some p r o c e d u r e s also exist for e s t i m a t i n g the p a v e m e n t t e m p e r a t u r e as a f u n c t i o n of d e p t h u s i n g the air t e m p e r a t u r e s of the p r e v i o u s five days and the current pavement surface t e m p e r a t u r e (Southgate and Deen, 1969) 6) The m e a s u r e d load m a g n i t u d e and m e a s u r e d and c a l c u l a t e d d e f l e c t i o n s for each basin u s e d to b a c k c a l c u l a t e layer moduli When a "representative" d e f l e c t i o n b a s i n is used, report the range of the actual values m e a s u r e d for each sensor 7) The e q u i v a l e n t layer elastic moduli of each s t r u c t u r a l layer for each b a c k c a l c u l a t e d b a s i n along with the m e a n and s t a n d a r d d e v i a t i o n for the d e s i g n s e c t i o n of each layer In some cases, the results are too few or are not n o r m a l l y - d i s t r i b u t e d , and o t h e r s t a t i s t i c a l tools m a y be more appropriate, such as m e d i a n values, o u t l i e r analyses, and f r e q u e n c y d i s t r i b u t i o n plots 8) For each layer moduli calculation, the a r i t h m e t i c absolute sum of p e r c e n t error or the root mean square p e r c e n t error b e t w e e n the m e a s u r e d and c a l c u l a t e d d e f l e c t i o n basins SUMMARY This d i s c u s s i o n provides the current status of the draft A S T M S t a n d a r d Guide for " C a l c u l a t i n g In Situ E q u i v a l e n t Elastic M o d u l i of Pavement M a t e r i a l s U s i n g L a y e r e d Elastic Theory" It r e p r e s e n t s the e i g h t h draft, u n p u b l i s h e d and u n c i r c u l a t e d in its p r e s e n t form We u n d e r s t a n d that if it were balloted, some more negative votes would s u r e l y result There are a n u m b e r of c o n t e s t e d points w h i c h have made this s t a n d a r d appear to be an impossible or at least improbable goal to attain Some of these items m a y not be a m a t t e r of simply c o m p r o m i s i n g our perspective; but, some could be a q u e s t i o n of d e a l i n g with incorrect, misleading, or u n k n o w n advice One of the most d e b a t a b l e issues is how to model a n o n - l i n e a r s t r e s s - d e p e n d e n t subgrade material The characterization from backcalculation, which includes the in-situ o v e r b u r d e n condition, p r o v i d e s a b e t t e r overall "average" than that o b t a i n e d from a small, u s u a l l y r e m o l d e d l a b o r a t o r y specimen However, since the outer sensor is u s e d for c a l c u l a t i n g this modulus, the c o r r e s p o n d i n g stress levels can be m u c h lower (and moduli higher) than those d i r e c t l y u n d e r the load This d i l e m m a has led some r e s e a r c h e r s to resort to d i v i d i n g the b a c k c a l c u l a t e d result by a factor of three to get the "correct" answer Even if past p e r f o r m a n c e p r e d i c t i o n m o d e l s were d e v e l o p e d u s i n g laboratory characterization of the subgrade modulus which tends to give lower values, there must be a better, m o r e s c i e n t i f i c a l l y - s o u n d a p p r o a c h to this problem A n u m b e r of other issues have also e v o l v e d which will h o p e f u l l y be a d d r e s s e d at this symposium These q u e s t i o n s are the following: i How we deal with surface cracks in p l a c i n g the N D T device and in c h a r a c t e r i z i n g the pavement m a t e r i a l p r o p e r t i e s (include or avoid)? How m a n y individual layers can we "reasonably" expect to b a c k c a l c u l a t e in an analysis? What is the m i n i m u m n u m b e r of d e f l e c t i o n readings r e q u i r e d for this analysis? At what d e p t h does the apparent stiff layer or b e d r o c k become Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions author 520 NONDESTRUCTIVE TESTING: SECOND VOLUME a critical input parameter? Is the modular ratio (Mr upper layer/ M r lower layer) of overlying layers a problem? How critical is Poisson's ratio? How critical are seed moduli? What is the best way of handling the many sources of longitudinal variability? Should every deflection basin be evaluated? Should the tolerance of fit vary by deflection sensor? REPERENCES American Association of State Highway and Transportation Officials (1986) AASHTO Guide for Desiqn of Pavement Structures 1986 Asphalt Institute (1982) "Research and Development of The Asphalt Institute's Thickness Design Manual (MS-l) Ninth Edition", Research Report No 82-2 Bush, Albert J III and Baladi, Gilbert Y (1989) Editors, N o n d e s t r u c t i v e Testinq of Pavements and B a c k c a l c u l a t i o n of Moduli, ASTM STP 1026 Hoffman, Mario S and Thompson, Marshall R (1982) "Backcalculating Nonlinear Resilient Moduli from Deflection Data", Transportation Research Record 852, pp.42-51 Lytton, R L., Germann F P., Chou Y J., and Stoffels, S M (1990) "Determining Asphalt Concrete Pavement Structural Properties by Nondestructive Testing," NCHRP Report No 327, National Cooperative Highway Research Program Shell International ~1978) Appendix of the Shell Manual, Shell International Petroleum Company Ltd Pavement Desiqn Southgate, H F and Deen, R C (1969) "Temperature Distribution within Asphalt Pavements and Its Relationship to Pavement Deflection", HRB Record 291, pp 116-131 Van Cauwelaert, F J., D R Alexander, W R Barker, and T D White (1989) "A Competent Multilayer Solution and Backcalculation Procedure for Personal Computers, Nondestructive Testinq of Pavements and Backcalculation of Moduli, ASTM STP 1026 Yoder, ~ , E J and Witczak, M W (1975) Principles published by John Wiley and Sons, Inc of Pavement Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized STP1198-EB/Dec 1994 Author Index A Akram, T., 170 Jackson, D J., 395 Jordahl, P., 38 B K Baker, M., 473 Baladi, G Y., 68 Boddapati, K M., 326 Brown, S F., 218 Krarup, J., 143 L Lenngren, C A., 361 Lepert, P., 277 Lytton, R L., 53, 159 C Caprioli, P., 277 Coetzee, N F., 233 Coree, B., 125 Crovetti, J A., 309, 455 M Magnuson, A H., 53, 159 Mahmood, T., 68 Mahoney, J P 233 Maser, K R., 343 May, R W., 505 McCaffrey, P S., Jr., 251 Murphy, M R., 395 D Darter, M I., 83 de Atmeida, J R., 218 Drnevich, V P., 125 F N Fernando, E., 343 Ferregut, C., 261 Nazarian, S., 261, 326, 473 Newcomb, D E., 361 G R George, K P., 203 Gucunski, N 380 Raab, A R., 68 Rada, G R., 38 Reddy, S., 473 Richter, C A., 38 Roddis, W M K., 343 Roque, R., 440 H Hall, J W., Jr., 251 Hall, K T., 83 Harichandran, R S., 68 Hiltunen, D R., 440 Holikatti, S., 291 Hudson, W R., 488 Scullion, T., 170, 343 Sebaaly, P E., 291 Shahin, M Y., 309 Smith, R E., 170 Stubbs, N., 53, 159 Stubstad, R N., 233 I Ioannides, A M., 103 521 Copyright by9ASTM (all International rights reserved); Sun Dec 27 14:44:10 EST 2015 Copyright 1994 byInt'l ASTM www.astm.org Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 522 NONDESTRUCTIVE TESTING OF PAVEMENTS T Thom, N H., 218 Tia, M., 404 Tirado-Crovetti, M R., 455 Torpunuri, V S., 53, 159 U Uddin, W., 203, 488 Ullidtz, P., 143 Uzan, J., V Van Deusen, D A., 361 Vennalaganti, K M., 261 Von Quintus, H L., 505 W Wahlman, T., 143 White, T D., 125 Wimsatt, A., 395 Wu, C.-L., 404 Z Zaghloul, S M., 125 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized STP1198-EB/Dec 1994 Subject Index A Accelerometers, 380 Aircraft pavement, 233, 251 Analysis of variance, 125 Annular loading, 309 Asphalt concrete, 3, 170 Asphalt layer moduli, 309 Asphalt overlaid concrete, 83 Asphalt pavements, 233 ASTM standard, deflection, 505 Deflection transfer efficiency, 440 Deflectometers, multidepth, 170 Density, effect on strength, 251 Dispersive methods, 277 curves, Rayleigh waves, 380 Dynamic analysis techniques, 3, 125 Dynamic excitation, 53 Dynamic linear technique, Dynamic nonlinear modulus, 3, 125 B E Base thickness, 343 BISDEF, 203 Bulk modulus model, C California Bearing Ratio, 251 Coefficient of dowel/concrete interaction, 440 COLIBRI, 277 Composite pavement structures, 83 Concrete pavement, 404, 473 joints, 395 slab on grade system, 103 slabs, 440, 455 Creep curve, 53 Critical stress method, 404 I) Damping, 53 Deflection analysis, 83, 143, 170, 203, 218 ASTM standards for, 505 effects on, 395 support, 455 surface, 440 void measurement with, 488 Deflection basins, 291 theoretical, 68 Elastic analyses, linear, 170 Elastic joints, 404 Elastic layer, 68, 505 Elastic linear program, 326 Elastic moduh', 53, 380, 404 in situ test, 38 Minnesota Road Research Project, 361 Elastic stiffness, 218 ELSDEF, 203 ELSYM5, 309 EVERCALC, 68 F Falling weight deflectometer, 143, 170 aircraft base, 251 concrete pavement, 404 elastic stiffness with, 218 embankment tests, 361 granular/subgrade characterization, 203 jointed concrete slabs, 440, 455 loading system, 326 load transfer efficiency, 395 material property, 53 methodology verification, 159 multilayer analysis, 125 phase lag effects, 291 slab-on-grade concrete, 103 523 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 524 ONDESTRUCTIVE TESTING OF PAVEMENTS FEACONS, 404 FEAD, 218 Filtering criteria, 380 Finite element analysis, 125, 218, 326, 440 FEACONS, 404 Flexible pavement, 203, 233, 261, 326, 505 Foundation moduli, 83 Foundation support moduli, 103 Foundation support value, 455 FPEDD1/RPEDD1, 203 Frequency domain, 159 dynamic linear with, Frequency response curves, 159 G Gauss-Newton method, 218 Geophones, 395 Gradient method, 68 Ground penetrating radar equipment, 488 Grout, 488 H Heavy weight deflectometer, 233 Horn antenna radar, 343 Impedance, 277 Impulse loading equipment, 309 Impulse response, 473 Load distributions, 309 Load effects, truck, 170 Loading, 251 annular, 309 assumptions versus actual, 125 vertical circular, 380 Load level choice, 233 Load, peak, 291 Load transfer efficiency, 395 Long-Term Pavement Performance, 38 M MICHBACK, 68 Minnesota Road Research Project, 361 MODCOMP2, 203 Models, 125, 218 annular loading, 309 bulk modulus, layered viscoelastic halfspaces, 53 pavement response, 143 strain softening, 203 MODULUS, 68, 203 Modulus of elasticity, 53 Moisture, 251 Monte Carlo simulation technique, 261 Multidepth deflectometers, 170 N J Joints, pavement, 395, 440 L interaction, 395 ered media, 159, 277 ered system, 261, 361 analysis, 125, 277 thickness measurement, 380 Layered viscoelastic halfspaces, 53, 159 LEAD, 218 Linear methods, 3, 326 Load, applied, 326 •Laier Newton method, 68 Gauss-Newton method, 218 Nonlinear elastic, static method, Nonlinear models, 125, 218 Nonlinear response, 203, 233 O Overburden, 218 Overlays, 83 design, 233 thickness, 291 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized INDEX 525 P Peak load, 291 Penetrometer soundings, dynamic cone, 361 Phase lag, 291 Plate sensor, 103 Poisson's ratio, 261, 395 Pore pressure, 218 Portland cement concrete, 488 Pressure distribution, 326 Proof roller, 488 R Radar, thickness evaluation, 343 Rayleigh waves, 380 Regression analysis, 125 Remaining life, 261, 326, 488 Resilient moduli, 203, 361 Rigid pavement, 326, 473 Seismic methods, 380 Shear strain attenuation curve, 203 Slab moduli, 83 Slab-on-grade system, 103 Spectral analysis of surface waves, 380 Standards, ASTM, 505 Static linear elastic technique, Stochastic analysis, 261 Strategic Highway Research Program, 3, 38, 103 Strain softening models, 203 Strains interfaces, 261 laboratory versus in situ tests, 361 Strains, subgrade, 170, 203 Stress analysis, critical, 404 Stress sensitivity, effect on tests, 233 Structural capacity, 38 Subbase support, 395, 404, 455, 473, 488 Subgrade reaction, 440 Subgrade strains, 125, 170, 203, 218, 361 Surface deflection, 309, 440 T Thickness layer, 68, 125, 380 pavement, 343 Time domain, 159 dynamic linear with, Transient dynamic response equipment, 488 V Voids determination, 473 measuring, 488 W Wave propagation, 277 Copyright by ASTM Int'l (all rights reserved); Sun Dec 27 14:44:10 EST 2015 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized