FLEXIBLE PAVEMENTS DEFLECTION-COVERAGE RELATIONSHIP FOR. ?1-s9~ A. H. Joseph, J. W. Hall, Jr. IBiLE 0I0 0 UN IVERSIAT UBNCHMIN. etz Refer.

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1 38ms?1-s9~ MISCELLANEOUS PAPER S DEFLECTION-COVERAGE RELATIONSHIP FOR FLEXIBLE PAVEMENTS by A. H. Joseph, J. W. Hall, Jr. fii l IBiLE I rk etz Refer UN IVERSIAT UBNCHMIN ence Room AT URBANA-CHAMPAIGN ivil Engineering epa ENGINEERING 16 C. E. Bull? ing niversity of Illinois June 1971 Jrbana, Illinois 6181 Sponsored by Office, Chief of Engineers, U. S. Army Conducted by U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED retadc339 79

2 Destroy this report when no longer needed. it to the originator. Do not return The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

3 MISCELLANEOUS PAPER S DEFLECTION-COVERAGE RELATIONSHIP FOR FLEXIBLE PAVEMENTS by A. I. Joseph, J. W. Hall, Jr. June 1971 Sponsored by Office, Chief of Engineers, U. S. Army Conducted by U. S. Army Engineer Waterways Experiment Station, Vicksburg, Mississippi ARMY-MRC VICKSBURG, MISS. APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

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5 THE CONTENTS OF THIS REPORT ARE NOT TO BE USED FOR ADVERTISING, PUBLICATION, OR PROMOTIONAL PURPOSES. CITATION OF TRADE NAMES DOES NOT CONSTITUTE AN OFFICIAL EN- DORSEMENT OR APPROVAL OF THE USE OF SUCH COMMERCIAL PRODUCTS. iii

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7 Foreword Authority for performance of the study reported herein is contained in Long-Range Program, &M, A, FY 1969 and FY 197, Project Q6-1, Task 8, Work Unit 9. The study was accomplished by personnel of the Soils Division, U. S. Army Engineer Waterways Experiment Station (WES), during the period July 1968-March 197. Engineers actively engaged in the collection and analysis of data were Messrs. A. H. Joseph and J. W. Hall, Jr. The overall study was under the general supervision of Messrs. W. J. Turnbull, J. P. Sale, A. A. Maxwell, and R. G. Ahlvin. Directors of the WES during the conduct of the study and the preparation of this report were COL Levi A. Brown, CE, and COL Ernest D. Peixotto, CE. Technical Directors were Mr. J. B. Tiffany and Mr. F. R. Brown. V

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9 Contents Foreword Conversion Factors, British to Metric Units Summary of Measurement. Introduction Background Sources of Data V Page ix xi Airfield Test Pavements Stockton test No Barksdale test section Stockton test No Multiple-wheel heavy gear load (MWHGL) Heavy gear loads pilot test section test section Highway Test Pavements WASHO test AASHO test Arkansas highway tests Virginia highway tests Analysis of Data Conclusions and Recommendations Literature Cited Tables 1-9 Plates 1-5 vii

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11 Conversion Factors, British to Metric Units of Measurement British units of measurement used in this report can be converted to metric units as follows: Multiply inches miles (U. S. statute) square feet pounds kips pounds per square inch Fahrenheit degrees By /9 To Obtain centimeters kilometers square meters kilograms kilograms kilograms per square centimeter Celsius or Kelvin degrees* * To obtain Celsius (C) temperature readings from Fahrenheit (F) readings, use the following formula: C = (5/9)(F - 32). To obtain Kelvin (K) readings, use: K = (5/9)(F - 32) ix

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13 Summary This study was conducted for the purpose of developing a relationship between elastic pavement deflection and pavement performance (number of traffic applications necessary to cause failure). Data for the study were taken from past studies of airfield and highway pavements. A summary of test conditions, failure criteria, and traffic type is given for each data source. A relationship was developed between elastic deflection and the number of coverages of traffic for combined airfield and highway data and for airfield data only. The relationship of wheel load and tire pressure is given, and a multiple-regression equation was determined to predict coverages as a function of wheel load, tire pressure, and deflection. xi

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15 DEFLECTION-COVERAGE RELATIONSHIP FOR FLEXIBLE PAVEMENTS Introduction 1. Pavement engineers have realized for many years that the response of a pavement to an applied load in terms of elastic deflection (rebound) is an indication of the ability of the structure to support the load. In this report, the term elastic deflection or deflection refers to the amount of vertical rebound of a pavement surface that occurs when a load is removed from the surface. Most of the research has been in the field of highway pavements, and several investigators have gone so far as to set limiting values for deflection. 2. Deflection is not directly considered in present Corps of Engineers (CE) criteria for design or evaluation of flexible pavements, but deflection measurements have been recorded on many test pavements at the U. S. Army Engineer Waterways Experiment Station (WES) and at various airfields. These data, along.with data from reported studies of deflections of highway pavements, form the basis for this report. The Office of the Chief of Engineers (OCE) instructed WES to initiate the subject study to extract information from these previous studies that might relate elastic pavement deflection to pavement performance. Such a relationship would have application to pavement design and nondestructive pavement evaluation. Background 3. Deflection has been measured on both highway and airfield pavements for quite some time, with the realization that these deflections had some relation to pavement performance. In 1955 Hveem1 published allowable values of elastic pavement deflections for various types of highway pavements in California. The work of Hveem was later extended to relate these allowable deflections to repetitions of traffic. Studies35' made in other countries have presented values of allowable deflections that are in general agreement with those established by Hveem. Engineers 1

16 concerned with airfield pavements have also noted that pavement deflections somehow indicate performance; deflection has been used to indicate shear deformation. Allowable elastic deflections for highways are generally given in the range of.2 to.3 in.,* but it has been felt that airfield pavements could withstand from.2- to.3-in, deflection. The reason that the allowable deflection for airfield pavements is so much greater than that for highway pavements is that an airfield carries only a few thousand repetitions of load during its life, whereas the number of repetitions on a highway is in the millions. Also, the allowable deflections under certain types of heavy aircraft loads may be greater because of the larger tire contact areas supporting the heavier loads, resulting in a flatter curvature of the pavement. Certainly, the degree of bending as well as the number of repetitions affects the life of the asphaltic surface. The magnitude of the surface deflection, which is the sum of the deflections that occur in all the layers of the pavement structure and the subgrade, indicates the degree to which each pavement component is strained by the imposed load. Sources of Data 4. Although allowable and critical elastic deflections for both highway and airfield pavements have been reported, literature relating such deflections to traffic characteristics and load repetitions is relatively scarce. The study reported herein was an attempt to bring together available information relating pavement surface deflections to the number of load repetitions necessary to cause failure. The following paragraphs give the referenced publications from which information was drawn and some pertinent facts about each source as to the methods used to measure deflections and to determine traffic characteristics and failure criteria. * A table of factors for converting British units of measurement to metric units is presented on page ix. 2

17 Airfield Test Pavements Stockton test No. 16'7 5. In March 1942, construction was begun on a pavement test section at Stockton Airfield near Stockton, California, by personnel of the California Division of Highways and of the U. S. Army Engineer District, Sacramento, CE. The test section was built over an old taxiway, which consisted of 6 in. of sand loam stabilized with asphalt emulsion over a weak adobe subgrade. The test section was surfaced with 3-in. asphaltic concrete over a crushed gravel base with the combined thickness of pavement and base varying from 6 to 42 in. Traffic was applied in two lanes with a 25,- and a 4,-lb single-wheel load. 6. Elastic deflection, defined as the total vertical movement during any one application of a load, was measured with General Electric travel gages installed within the test section. 7. Failure was determined by visual observation of surface cracking and grooving (rutting). Grooving, at the time of failure, ranged between 1.5 and 2 in. in depth. Information taken from references 6 and 7 is shown in table 1. Barksdale test section 8 8. Barksdale Field, near Shreveport, Louisiana, was selected because of its uniform plastic clay subgrade as the site for one of a series of tests initiated by OCE to obtain data for development of design procedures for flexible pavements placed on various types of subgrades to support heavy wheel loads. Traffic testing on each of the test tracks at Barksdale was performed during February and March 1943 with 2,- and 5,-lb single-wheel loads. 9. General Electric travel gages were used to measure elastic deflections. Failure was defined as: "...the development of a definite crack pattern in the 3-in. asphaltic concrete pavement under the action of repeated loads. The initial stage is generally evidenced by fine cracks; as tracking continues, deep, wide cracks develop; and finally the wide cracks run into each other breaking the pavement into individual pieces." 3

18 1. A sharp increase in deflections to as much as.5 in. followed by a decrease was noted for several of the test items at Barksdale. The Barksdale report notes a period of "water pumping" during these periods of increased deflections. This could have been caused by development of excess pore pressure in the subgrade material. Information taken from the Barksdale report is given in table 2. Stockton test No In 1945, a second test section was constructed at Stockton Field, California, by the Sacramento District, CE. This test section consisted of 26 items, each with a different design constructed over three subgrades of different strengths with various thicknesses of base and subbase and with asphaltic concrete varying in thickness from 2-1/2 to 16 in. 12. Deflection gages similar to those used in the first Stockton test and in the Barksdale test were used. July 1946 and February Traffic was applied between After approximately 25 coverages with a 15,-lb single wheel, the test load was increased to 2, lb. Failure of the test items was determined in a manner similar to that in the first Stockton test. table 3. Information taken from reference 9 is shown in The coverages to failure shown in the table are a combination of coverages of the 15,-lb wheel load and the 2,-lb wheel load converted to terms of an equivalent number of coverages of the 15,-lb load. the CE. 1 This was accomplished through use of the CBR design equation of Multiple-wheel heavy gear load (MWHGL) test section 13. From July 1968 to November 1969, test pavements were constructed at WES and trafficked to determine if present criteria were adequate for design of pavements to accommodate large multiple-wheel aircraft such as the C-5A. For comparison purposes, single-wheel traffic was applied to some of the test sections. Results of the single-wheel traffic that caused pavement failure are shown in table The test pavements consisted of a 3-in. asphaltic concrete surface, a 6-in. crushed stone base, a sand-gravel subbase that varied in thickness for each test item, and a heavy clay (CH) subgrade. Traffic was '4

19 applied at pavement temperatures above 9 F. Deflection measurements were taken in items 1 and 2 with a precision rod and level to determine the deflection basin to the edge of the load wheel. These measured deflections were then extrapolated to give the maximum deflection at the center of the tire. The ratios of theoretical deflection factors for deflection of a homogeneous elastic half-space under uniform circular loading11 were used for the extrapolation. The pavements were considered failed when cracking of the asphaltic concrete had progressed to the point at which the surface was no longer waterproof or at which upheaval of the pavement surface at the edge of the traffic lane had reached 1 in. Results of the MWHGL test pavements will be published soon. Heavy gear loads pilot test section This test section, authorized by the U. S. Air Force and constructed at WES in the fall of 1956, consisted of 4 in. of asphaltic concrete, 7 in. of 3-CBR crushed limestone, 12 in. of 1-CBR crushed limestone, a 6 -in. layer of old pavement, and 7 in. of 45-CBR crushed limestone, making a 3 6 -in. pavement structure over a 2- to 3-CBR subgrade. Traffic was applied to items 2, 23, and 26 with a 128,-lb twin-wheel assembly. Deflections were measured on the pavement in both the loaded (between the dual wheels) and the unloaded conditions, using a level instrument to read rods placed in a prearranged position on the pavement. 16. Failure was described as either severe cracking or severe rutting. When cracking had progressed to the point that the pavement was no longer effectively waterproof, it was considered to be severe. When the pavement became unserviceable or hazardous for use by aircraft because of rutting, then rutting was termed severe. Table 5 gives information taken from this study. The deflections shown in the table were corrected in a manner given later in this report to represent the deflection at the center of the wheel load. Highway Test Pavements WASHO test In the summer of 1952, a test road comprised of two test loops 5

20 was constructed in southern Idaho. One test loop consisted of 4 in. of asphaltic concrete, 2 in. of base, and from to 16 in. of subbase; the other loop was made of 2 in. of asphaltic concrete, 4 in. of base, and to 16 in. of subbase. Both loops were built over a silt loam to silty clay loam subgrade. Traffic was applied between November 1952 and May Deflections were measured with the Benkleman beam under the regular test traffic of tractor-semitrailer combinations with the tractor drive axles and trailer axles loaded to specified weights. Creep-speed deflections measured during the period 1 June to 7 July 1953 were used for this study. 19. Failure criteria were difficult to determine from the WASHO report, but for this study, failure was considered to have occurred at the time when 16 to 18 sq ft of deep patching had been placed in any one test section. Table 6 presents information taken from the WASHO report. AASHO testlh 2. In August 1956, construction was begun on a highway test road located at Ottawa, Illinois. This test road consisted of four large loops and two small loops. Each loop was a segment of a four-lane divided highway. Loop 1 was an instrumentation pavement and was not trafficked. Traffic, consisting of tractor-semitrailer combinations except in loop 2 where small single-unit trucks were used, was applied between October 1958 and November 196. Every vehicle in any one of the traffic lanes had the same axle load and axle configuration. 21. Deflections were measured with the Benkleman beam, and creepspeed values recorded in October 1958 were used for this study. 22. Failure was assumed to have occurred at a Pavement Serviceability Index (PSI) of 1.5. Practically all cases of failure occurred during or at the end of the spring thaw period. study are shown in table 7. The AASHO data used in this Arkansas highway tests This study began in July 1958 on 115 miles of flexible pavement located in the loess-terrace soil in eastern Arkansas. Deflections were measured at creep speed with the Benkleman beam under an 18,-lb singleaxle dual-wheel load. Traffic was given in terms of equivalent 5-lb 6

21 wheel loads. Failure was determined from a condition survey rating and from statements in reference 15 pertaining to the condition of the pavement. Information from reference 15 is given in table 8. Virginia highway tests Tests were made in the spring of 1962 on highway pavements in Virginia. Rebound deflections were measured with the Benkleman beam under an 18,-lb, single-axle, dual-wheel load. Traffic is given in terms of average daily volumes of trailer trucks and buses. Time from the year that the pavement was opened to traffic to the year that it was resurfaced due to pronounced cracking was taken as the life of the pavement. This time was multiplied by the average daily traffic to obtain an estimate of the total traffic. This information is given in table 9. Analysis of Data 25. Many factors affect the deflection of a pavement and the measurement of this deflection. Pavement surface deflections are dependent on such factors as gross load, tire pressure, wheel configuration, and rate of loading, as well as the pavement's structural strength and thickness of the asphaltic surfacing. Deflection of a pavement under identical loading conditions may vary due to such factors as temperature, subgrade moisture changes, hardening of the asphalt, and additional compaction of the pavement layers due to traffic. 26. The data accumulated in this study were certainly affected by the above-mentioned factors although most of the data were taken from controlled test pavements. Deflection data shown in tables 1-8 were measured at creep speeds during the early life of the pavements. The deflections shown in tables 5-8 were measured between dual wheels, and these values were extrapolated to give the deflection at the center of one of the wheels by using the ratio of theoretical deflection factors for a uniform circular load on a homogeneous elastic half-space. The deflection between a set of dual wheels was increased by the ratio of the deflection factor beneath one of the wheels of the dual assembly to the factor at the center of the dual assembly. The highway data were given in number of individual load 7

22 repetitions, whereas coverages were used to give the number of loadings on most of the airfield pavements. A coverage is one repetition of the test load applied to every point in a given traffic lane. Repetitions-percoverage factors developed by the WES1 were used to change all of the traffic information to coverages. No correction was made for temperature, but most data were taken during warm periods with ambient temperatures of about 7 to 8 F. Plate 1 presents a graphical analysis of elastic deflection and number of coverages at failure for both highway and airfield pavements. (Failure criteria for each source of information have previously been described.) The ranges showing one standard error of estimate are shown in plate 1. The correlation coefficient for these data is.73. The equation for the best-fit line is D = C (1) where D = elastic deflection, in. C = coverages to failure Plate 2 is similar to plate 1 except that only data from airfield test pavements are presented. For the airfield data, the correlation coefficient is.64, and the equation for the best-fit line is D =.9523C (2) 27. Attempts were made to reduce the scatter of the data points in plates 1 and 2 by introducing various combinations of tire pressure, wheel load, and strength of the pavement structure. best fit for each set of the airfield data. Plate 3 gives the line of Indications here are for the heavier wheel loads to be at the top of the plot and for lighter loads and higher tire pressure to be near the bottom. A multiple-regression analysis was made of the airfield data, and a plot of actual coverages versus predicted coverages from the regression equation considering deflection, wheel load, and tire pressure is shown in plate 4; a correlation coefficient of.8 was obtained. The multiple-regression equation is 8

23 .2166Pl 3344 (3) C = p D where C = coverages to failure P = single-wheel load, lb p = tire pressure, psi D = elastic deflection, in. Plate 5 presents the results of the multiple regression of coverages as a function of deflection, wheel load, tire pressure, subgrade CBR, total pavement thickness above the subgrade, and thickness of the asphaltic concrete layer. This relationship gave a correlation coefficient of.84 and a prediction equation of ) O.716)4T P CBR T p D where C = coverages to failure TT = thickness of total structure above subgrade, in. CBR = California Bearing Ratio of subgrade P = single-wheel load, lb p = tire pressure, psi D = elastic deflection, in. 28. Some of the scatter is probably due to variations in failure criteria, capability of measuring precise elastic deflection at the center of a wheel load, and environmental factors. Some of the highway pavements, such as those in the AASHO tests, were affected by freeze-thaw cycles, but this was not a factor in the airfield pavements. The shape of the deflection basin, i.e., the radius of curvature, plays an important part in the life of the pavement surface. Such information was not available for this study. Various conditions of loading on two pavements of different strength could produce situations of equal deflection beneath the wheel 9

24 but with unlike deflection basin shapes. Therefore, some of the variation of data points in this study may be due to radii of curvature or to shearing strain. Conclusions and Recommendations 29. This study shows that there is a definite relationship between the elastic deflection beneath a wheel load and the number of repetitions of that load necessary to cause failure of the pavement. This relationship, although not very precise, is surprising in consideration of the number of variables involved. The relationship given in this report incorporates many loading conditions and various pavement structural types, as well as a variety of environmental conditions. The relation is adversely affected by the lack of uniform failure criteria, and no consideration was given to the type of failure, i.e., whether a shear failure in the subgrade or other pavement component or fatigue failure of the asphaltic concrete surfacing. 3. Results of future tests on airfield pavements test sections that may be constructed and tested, as well as data from the highway field, should be used to further develop the deflection-performance relationship presented in this report. In the future, measurements of the deflection basin, as well as deflection beneath the wheel load, should be made, since the degree of bending of the pavement surface probably has a great effect on the pavement life. 31. The results of this study, especially if further refined in consideration of additional data, can be useful in the development and application of theoretical pavement design methods and in nondestructive testing to evaluate flexible pavements. If pavement deflections derived from layer theories could be related to measured prototype deflections, then the results of the present study would create the link between theory and actual pavement performance. 1

25 Literature Cited 1. Hveem, F. N., "Pavement Deflections and Fatigue Failures," Bulletin No. 114, pp 43-74, 1955, Highway Research Board, Washington, D. C. 2. Zube, E. and Forsyth, R., "Flexible Pavement Maintenance Requirements as Determined by Deflection Measurements," Record No. 129, pp 6-75, 1966, Highway Research Board, Washington, D. C. 3. Carneiro, F. B. L., "Benkleman Beam--Auxiliary Instrument of the Maintenance Engineer," Record No. 129, 1966, Highway Research Board, Washington, D. C. 4. Lister, N. W., "Deflection Measurements on the Experimental Sections on A.l near Boroughbridge (N. Riding)," Laboratory Note LN/247/NWL, 1963, Department of Scientific and Industrial Research, Road Research Laboratory, Great Britain. 5. Foster, C. R. and Ahlvin, R. G., "Failure Criteria for Flexible Airfield Pavements," Bulletin No. 187, pp 72-75, 1958, Highway Research Board, Washington, D. C. 6. Porter,. J., "Report on Stockton Runway Test Section," Sept 1942, U. S. Army Engineer District, Sacramento, CE, Sacramento, Calif. 7., "Test Section No. 1, Stockton Field, California," Proceedings, American Society of Civil Engineers, Vol 75, Paper No. 1, U. S. Army Engineer District, Little Rock, CE, "Service Behavior Test Section, Barksdale Field, Louisiana," Oct 1944, Little Rock, Ark. 9. Porter,. J., "Accelerated Traffic Test at Stockton Airfield," Mar 1948, U. S. Army Engineer District, Sacramento, CE, Sacramento, Calif. 1. Ahlvin, R. G., "Developing a Set of CBR Design Curves," Instruction Report No. 4, Nov 1959, U. S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss. 11. Ahlvin, R. G. and Ulery, H. H., "Tabulated Values for Determining the Complete Pattern of Stresses, Strains, and Deflections Beneath a Uniform Circular Load on a Homogeneous Half Space," Bulletin No. 342, pp 1-13, 1962, Highway Research Board, Washington, D. C. 12. Burns, C. D. and Womack, L. M., "Pavement Mix Design Study for Very Heavy Gear Loads, Pilot Test Section," Technical Report No , Feb 1962, U. S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss. 13. Highway Research Board, "The WASHO Road Test; Part 2--Test Data and Analyses and Findings," Special Report No. 22, 1955, Washington, D. C. 14., "The AASHO Road Test Report No. 5," Special Report 61E, 1962, Washington, D. C. 11

26 15. Ford, M. C. and Bissett, J. R., "Flexible Pavement Performance Studies in Arkansas," Bulletin No. 321, pp 1-15, 1952, Highway Research Board, Washington, D. C. 16. Nichols, F. P., Jr., "Deflections as an Indicator of Flexible Pavement Performance," Record No. 13, pp 46-65, 1963, Highway Research Board, Washington, D. C. 17. Brown, D. N. and Ahlvin, R. G., "Revised Method of Thickness Design for Flexible Highway Pavements at Military Installations," Technical Report No , Aug 1961, U. S. Army Engineer Waterways Experiment Station, CE, Vicksburg, Miss. 12

27 Table 1 Results of Stockton Test No. 1 Single- Tire Test Section Pavement Thickness, in. Coverages Average Wheel Pressure Deflection Asphaltic Total at Deflection Subgrade Load, lb psi Station Point Concrete Structure Failure in. CBR 25, , Table 2 Results of Barksdale Field Tests Coverages Elastic Single- Tire Test Section Pavement Thickness, in. At Time of Deflec- Sub- Wheel Pressure Item Deflection Asphaltic Total Deflection At tion grade Load, lb psi No. Plug Concrete Structure Measurement Failure in. CBR 2, a b , a b Table 3 Results of Stockton Test No. 2 Coverages Single- Tire Test Pavement Thickness, in. At Time of Elastic Wheel Pressure Section Asphaltic Total Deflection At Deflection Subgrade Load, lb psi Item No. Concrete Structure Measurement Failure* in. CBR 15, A B A B * Equivalent coverages of 15,- and 2,-lb wheel in terms of 15,-lb wheel load.

28 Table 4 Results of Tests on Multiple-Wheel Heavy Gear Load (MWHGL) Test Section Single- Tire Test Pavement Thickness, in. Coverages Elastic Wheel Pressure Section Asphaltic Total at Deflection Subgrade Load, lb psi Item No. Concrete Structure Failure in. CBR 3, , Table 5 Results of Tests on Heavy Gear Loads Pilot Test Section Coverages Tire At Time of Wheel Pressure Test Section Deflection At Deflection, in. Load, lb psi Lane Item Measurement Failure Measured Corrected 128, 24 B * (Dual) B ** B ** Failed by severe cracking of surface. ** Failed by severe rutting of surface. Table 6 WASHO Road Test Data Wheel Path Applications of Test (Inner or Traffic Prior to Equivalent Deflection, in. Section* Outer) Major Distress** Coverages Measured Corrected s I 185 x 13 7, S 185 x 13 7, S 16 x l3 67, S 18 x 13 68, S 18 x 13 75, T 18 x 13 17, T 138 x , l-2-32t 185 x , l-2-4t 18 x 13 17, l-2-4t I 185 x , * Test section numbers indicate total thickness of pavement structure in inches, thickness of asphaltic concrete surface in inches, wheel load in kips, and axle type--s (single axle) and T (tandem axle). All tire pressures were 75 psi. ** Condition of major distress taken as 16 to 18 sq ft of deep patching.

29 Equivalent Deflection, in. Coverages Measured Corrected Axle Load kips 6 Tire Pressure psi 45 Test Loop Section (Continued) Pavemer.t Thickness, in., o o o-o o o (4-1 /2-2)-o 3-(i4-11)-o 3-(11-8)- 3-(8-5) 3-(5-2)- 3-(14-i1)- 3-(11-8)-o 3-(8-5)- 3-(5-2)- 3-(4-1/2-2)- 3-(11-8)- 3-(8-5)- 3-(5-2)-o 3-(14-11)-o 3-(8-5)- 3-(5-2) Wheel Path (Inner or Outer) I, C C C I, C I I S, AA5OI Test Data Applications of Traffic at Pavement Serviceability Index of ,5 58,7 551,2 1,7 3,3 78, 117,9 18,1 551,2 58,7 15,3 183,2 16,8 75, 715,6 89,5 11, 71,3 69,5 89,5 89,5 78,4 623, 5,3 77,5 568,ooo 598,8 77,5 73,2 77,5 79,5 71,4 82,8 72,6 18,3 18,3 18,3 71,3 93,4 9,7 149,2 89,5 69,5 316,7 559,4 111, 77,5 73,3 774,7 553,7 9,7 7,1 182,6 553,7 14,5 88,1 581,9 126,7 78,4 12,9 12,9 11, 125,3 113,9 117,7 468, 73,3 73,3 7,9 73,9 71,4 11,9 113,9 113,9 17,2 149,2 49, 49, 117,7 114,3 84,5 71,4 1,47,9 132, 261,9 19,9 186,8 6 1,1 26,4 4, 36,7 186,8 19,9 35,7 62,1 36,2 25,4 242,6 33,9 38,3 265,6 26,4 33,9 33,9 29,7 236, 2, 29,4 215,2 226,8 29,4 27,8 29,4 3,1 27,1 31,4 27,5 41,1 41,1 41,1 265,6 35,4 34,4 56,5 33,9 26,4 12, 211,9 42,1 29,4 27,8 293,4 29,7 34,4 26,6 69,2 29,7 39,6 33,4 22,4 48,ooo 29,7 39, 39, 38,3 47,5 43,1 44,6 177,3 27,8 27,8 26,9 28, 27,1 38,6 43,1 43,1 4,6 56,5 185,6 185,6 44,6 43,3 32, 265,7 396,9 5, o.o o o.o * Each entry indicate, asphaltic concrete, bate course, and subbase thicknesses. (1 of 3 sheets)

30 Axle Load kips Tirr> Pres- sure psi (Continued) Loop Test Section Pavement, Thickness, in ( /4)-4 3-(14-1/4-1-1/2)-4 3-(1-1/2-6-3/4)-4 3-(6-3/4-3)-4 3-(6-1/4-3)-4 3-(9-3/4-7-1/2)-4 3-(7-1/2-5-1/4)-4 3-(5-1/4-3)-4 3-(6-1/4-3)-4 3-(9-3/4-7-1/2)-4 3-(7-1/2-5-1/4)-4 3-(8-14-1/4)-4 3-(6-3/4-3) (15-11)-8 4-(11-7)-8 4-(7-3)-8 4-(1o-1/2-8)-4 4-(8-5-1/2)-4 4-(5-1/2-3)-4 4-(1o-1/2-6-3/4)-4 4-(6-3/4-3)-4 4-(lo-1/2-6-3/4)-4 4-(6-3/4-3)-4 4-(7-3)-8 4-(1o-1/2-8)-4 4-(8-5-1/2)-4 4-(5-1/2-3) Wheel Applications Path of Traffic (Inner at Pavement or Serviceability Outer) Index of 1.5 O 59,2 I 77,2 77,2 I 59,2 I, 7, 11,5 11,5 11,5 11,5 81,7 81,7 I, 81,7 I, 77,2 I, 11,5 I, 11,5 I, 11,5 13,7 7, 36,4 85,6 85,6 75,5 67,1 123, I 614,9 I 275,6 I 8,4 121,8 I, 551,4 89,7 I 36,4 36,4 I, 1, 127,2 98,5 94,ooo 76,3 76,3 76,3 76,3 16,8 16,8 16,8 16,8 774,2 117, 79,1 662,7 117, 77,9 774,4 151,5 298,1 17,9 82,5 338,1 96,4 71,5 72,5 72,5 72,5 148,1 486,9 182, 14,7 117, 117, 574,5 626,7 99,5 11,4 11,4 626,7 148,1 74,5 1,98,4 182, 182, 626,7 774,4 486,9 588,1 94,9 17,9 7,4 7,4 Equivalent Coverages 25, 32,6 32,6 25, 29,5 42,8 42,8 42,8 42,8 34,5 34,5 34,5 32,6 42,8 42,8 42,8 43,8 29,5 15,4 36,1 36,1 31,9 28,3 51,9 259,5 116,3 33,9 51,4 232,7 37,8 15,4 15,4 53,7 41,6 39,7 32,2 32,2 32,2 32,2 45,1 45,1 45,1 45,1 326,7 49,4 33,4 264,4 49,4 32,9 326,8 63,9 125,8 45,5 34,8 142,7 4,7 3,2 3,6 3,6 3,6 62,5 25,4 76,8 44,2 49,4 49,4 242,4 264,4 383,8 42,8 42,8 264,4 62,5 31,4 463,5 76,8 76,8 264,4 326,8 25,4 248,1 4, 45,5 295,5 295,5 Deflection, in. Measured Corrected o o.o o o.o (3 of 3 sheets)

31 'ire Axle Pres- Load sure kips psi (Continued) Test Loop Section Pavement Thickness, in (8-6)-4 3-(6-4)-4 3-(4-2)-4 3-( /2)-4 3-(12-1/2-9)-4 3-(9-5-1/2)-4 3-(5-1/2-2)-4 3-(12-1/2-9)-4 3-(9-5-1/2)-4 3-(5-1/2-2)-4 3-(8-6)-4 3-(6-4)-4 3-(4-2)-4 3-(12-1/2-9)-4 3-(9-5-1/2)-4 3-(5-1/2-2)-4 3-(12-1/2-9)-4 3-(9-5-1/2)-4 3-(5-1/2-2) o o o o-4 5-o-4 5-o-4 5-o (Continued) Wheel Path (Inner or outer) 5, I I 1, I Application of Traffic at Pavement Serviceability Index of ,7 8,6 112,3 98,5 589,2 95,7 112,8 75,2 774,4 149,4 94,4 74, 621,6 588,8 17,3 97,6 774,4 88,5 647,9 488,7 2,6 636, 98,5 81,9 466,7 14,9 88,5 59,8 149,4 87,5 75,2 71,4 2, 75,8 118,4 86,1 5,5 336,3 83,4 76,7 4,5 7,3 7,3 7,3 79,6 87,5 87,5 83,4 98,6 12,5 1, 97,6 11,4 98,5 11,4 16,6 7,3 7,3 7,3 7,3 14,9 16,6 113,4 1, 7,7 89,7 372,9 76,1 16,5 1,4 625,7 77,2 94, 78,5 972,2 94, 767,9 75,5 73,8 94,ooo 625,7 94, 625,7 697,9 84,6 488,1 36,4 77,2 Equivalent Coverages 29,8 3,5 42,5 37,3 223,2 36,3 42,7 28,5 293,3 56,6 35,8 28, 235,5 223, 4,6cc 37, 293,3 33,5 245,4 185,1 1, 24,9 37,3 31, 176,8 39,7 33,5 22,7 56,6 33,1 28,5 265,7 75,8 28,7 44,8 32,6 2,1 127,4 31,6 29,1 1,7 26,6 26,6 26,6 3,2 33,1 33,1 31,6 37,3 38,8 37,9 37, 38,4 37,3 38,4 4,4cc 26,6 26,6 26,6 26,6 39,7 4,4cc 43, 37,9 29,8 37,8 157,3 32,1 44,9 42,4cc 264, 32,5 39,7 33,1 41,2 39,7 324,ooo 31,9 31,1 39,7 264, 39,7 264, 294,5 35,7 26, 15,4 32,6 Deflection, in. Measured Corrected o o.o o (2 of 3 sheets)

32 Table 8 Arkansas Highway Test Data Tire Traffic Pressure Equivalent Deflection, in. Load, lb psi Repetitions Coverages Measured Corrected 18,* 9 1,743, 277, , 111, , 73, , 16, , 3, * Single axle, dual wheels. Table 9 Virginia Highway Test Data Pavement Pavement Age Tire Thickness, in. Traffic at Deflection Pres- Asphal- Total Equivalent Fail- in. Load sure tic Struc- Daily Coverages ure Meas- Corlb psi Concrete ture Avg** at Failure years ured rected 18,* , , ,631, ,715, ,342, , * Single axle, dual wheels. ** Trailer trucks and buses , , , ,5 < , , ,

33 " i If t r '-I- P I. _- FI -i-t- -k. -, r r I I _ -_-- ]4 STANDARD ERROR OF ESTIMATE -i i i i i i i i i i i I I i I i _ L_ ' I 77t - - ~~~~1 A-1 1 A i r- I I I I L I i I ---- Z V LJ. 1 ~-. I- J WU I {--- 4l- I I I i + 4 1! 1! 4! - I I I I I I I I - I I I i i i 1 i i i i +- I _- - lii i~~ -- J r -rte s '-r - T l o -i T e o 3, --Ur p --- v- lii V V V V_ T Y Y V 7 V V U T 7 v T v vy VY Y r ov Y T" -T "T V T I wv I 1 I-- - -I I Imo. 19 vif M I T I 1 1 IV tvt l I " Ilt Vi V I _ T V T c- O y -- I- T Y I I ' II 3n4 i i I i Tntft- + i i i i i i i i i i V TTU 1 i o oil.9 9 ~ -..._ \ )o I3 \4 15 COVERAGES TO FAILURE L i i i i i _ 16 LEGEND O STOCKTON I * STOCKTON 2 BARKSDALE VIRGINIA HIGHWAY V WASHO V AASHO A PILOT TEST SECTION AMWHGL ARKANSAS HIGHWAY DEFLECTION VS COVERAGES SINGLE- AND MULTIPLE-WHEEL LOADS COMBINED HIGHWAY AND AIRFIELD DATA PLATE I

34

35 STANDARD ERROR OF ESTIMATE - *v.9 v e " Z U w J W& u I-. I e.11 I _ J _I. _ IIII _IIII I I I I I... _ I I I I I.1I_ I 1g 12 4 COVERAGES TO FAILURE LEGEND O STOCKTON I A STOCKTON I BARKSDALE V BARKSDALE WHEEL LOAD KIPS TIRE WHEEL PRESSURE LOAD PSI KIPS 55 " STOCKTON A MWHGL 5 63 MWHGL 3 71 TIRE PRESSURE PSI DEFLECTION VS COVERAGES SINGLE-WHEEL DATA AIRFIELD TEST PAVEMENTS P 'LATE 2

36

37 . MW/HGL, 5 KIPS, 165 PS/ STOCKTON 1, 4 K/PS, 59 PSI BARKSDAL E, 5 KIPS, 7 PSI z -S STOCK TON 2,15O KIPS, l PSI U wa J STOCKTON 1, 25 KIPS, 55 PSI U- U La BARKSDAL E, 2 KIPS, 63 PS1.3 L-- 4 X1 1' 12 ACTUAL COVERAGES 13 6X1 3 m DEFLECTION VS COVERAGES BEST-FIT LINES FOR INDIVIDUAL DATA SETS SINGLE-WHEEL DATA AIRFIELD TEST PAVEMENTS

38 / / I -U I- I4 ~ tieeii5eeeeieeei lee IIIIEEEEIiii{ L~IEE1IIEEEE""""I / 2flEI2IffiEEE~Y_ lielelieth /2 / I II 13 cr w U U W cr 12 ~ O E STDAEO_ ijj - OFESIMT -F - -T - 4 1' 1 1 O STOCKTON I A STOCKTON I BARKSDALE V BARKSDALE LEGEND 1, - CII/ WHE EL LOAD KIPS 25 * STOCKTON 2 4 A MWHGL 2 MWHGL 5 7) WHEEL LOAD KI PS ACTUAL COVERAGES PREDICTED VS ACTUAL COVERAGES MULTIPLE-REGRESSION ANALYSIS SINGLE-WHEEL DATA AIRFIELD TEST PAVEMENTS CORRELATION COEFFICIENT.8

39 14 Ilk V) W wd F- Y a Id a IV STANDARD ERROR OF ESTIMATE - -U m -I 1 1 WHEEL LOAD KIPS O STOCKTON I 25 SSTOCKTON I 4 BARKSDALE 2 V BARKSDALE 5 LEGEND 1' 12 WHEEL LOAD KIPS STOCKTON 2 15 A MWHGL 3 MWHGL 5 ACTUAL COVERAGES PREDICTED VS ACTUAL COVERAGES MULTIPLE-REGRESSION ANALYSIS SINGLE-WHEEL DATA AIRFIELD TEST PAVEMENTS CORRELATION COEFFICIENT.84

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41 DISTRIBUTION LIST FOR MISCELLANEOUS PAPER S Address No. of Copies Chief of Engineers, Department of the Army, Washington, D. C ATTN: ENGMC-ED 2 ENGME-RD 2 ENGPA 1 Library 1 Commanding General, U. S. Army Materiel Command, Washington, D. C ATTN: AMCRD-T 2 AMCRL 2 Commanding Officer, USACDC Engineer Agency, 1 Fort Belvoir, Va. 226 The Engineer School, Technical Information Branch, 1 Archives Section (Building 27), Fort Belvoir, Va. 226 Director, U. S. Army Terrestrial Sciences Research Center, 1 P.. Box 282, Hanover, N. H ATTN: AMXCR-EC Director, U. S. Army Construction Engineering Research 2 Laboratory, P.. Box 45, Champaign, Ill Each Division Engineer, U. S. Army Engineer Division ATTN: Library 1 Chief, Engineering Division 1 Laboratory 1 Each District Engineer, U. S. Army Engineer District ATTN: Library 1 Chief, Engineering Division 1 Chief of Staff, United States Air Force, Washington, D. C. 233 ATTN: Director of Civil Engineering 1 AF/PREES 1 Director, Air Force Weapons Laboratory, 1 Kirtland AFB, N. Mex ATTN: WLDC Commander, Civil Engineering Center, 1 Wright-Patterson AFB, Ohio ATTN: AF/PREC 1

42 Address No. of Copies Chief, Naval Facilities Engineering Command, Department of 1 the Navy, Washington, D. C. 235 ATTN: Chief Engineer Officer-in-Charge, U. S. Naval Civil Engineering Research and 1 Evaluation Laboratory, Construction Battalion Center, Port Hueneme, Calif Defense Documentation Center, Cameron Station, 12 Alexandria, Va ATTN: Mr. Meyer Kahn Federal Aviation Agency, 8 Independence Avenue, Washington, D. C ATTN: Chief, Airports Standard Division--AS58 1 Office of Management Services, MS111 Highway Research Board, National Research Council, Constitution Avenue, Washington, D. C Director of Public Roads, Bureau of Public Roads, Department of Transportation, Washington, D. C ATTN: Library 1 Director, Research and Development 1 Chief Engineer 1 Engineering Societies Library, 345 East 47th Street, 1 New York, N. Y. 117 Professor Arthur Casagrande, Pierce Hall, Harvard University, 1 Cambridge, Mass Professor K. B. Woods, School of Civil Engineering, 1 Purdue University, Lafayette, Ind Professor Frank E. Richart, Jr., Department of Civil Engineering, 1 University of Michigan, 34 West Engineering, Ann Arbor, Mich Professor Ralph E. Fadum, School of Engineering, 1 North Carolina State College at Raleigh, Box 5518 Raleigh, N. C Professor Robert V. Whitman, Room 1-343, Dept of Civil and 1 Sanitary Engineering, Massachusetts Institute of Technology, Cambridge, Mass

43 Address No. of Copies Mr. Stanley D. Wilson, Shannon and Wilson, Consulting Engineers, North 38th Street, Seattle, Wash Library of Congress, Exchange and Gift Division, 2 Washington, D. C. 254 ATTN: American and British Section Superintendent of Documents, Division of Public Documents, 1 U. S. Government Printing Office, Washington, D. C. 242 Building Research Advisory Board, National Academy of Sciences, Constitution Avenue, Washington, D. C Professor Nathan M. Newmark, University of Illinois, S. Pleasant Street, Urbana, Ill Dr. Philip C. Rutledge, Mueser, Rutledge, Wentworth & Johnston, Madison Avenue, New York, N. Y. 117 Department of Civil Engineering, University of Illinois, Urbana, Ill ATTN: Professor Ralph B. Peck 1 Professor Chester P. Siess 1 Professor William H. Goetz, Joint Highway Research Project, 1 Civil Engineering Building, Lafayette, Ind Professor John F. McLaughlin, School of Civil Engineering, 1 Purdue University, Lafayette, Ind

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45 TTnra ngni fi Prl Security Classification DOCUMENT CONTROL DATA - R & D (Security classification of title, body of abstract and indexing annotation must be entered when the overall report Is classified) 1. ORIGINATING ACTIVITY (Corporate author) 2a. REPORT SECURITY CLASSIFICATION U. S. Army Engineer Waterways Experiment Station Unclassified Vicksburg, Mississippi 2b. GROUP 3. REPORT TITLE DEFLECTION-COVERAGE RELATIONSHIP FOR FLEXIBLE PAVEMENTS 4. DESCRIPTIVE NOTES (Type of report and inclusive dates) Final report s. AU THOR(S) (First name, middle initial, last name) Alfred H. Joseph Jim W. Hall, Jr. 6. REPORT DATE 7a. TOTAL NO. OF PAGES 7b. NO. OF REFS June Sa. CONTRACT OR GRANT NO. a. ORIGINATOR'S REPORT NUMBER(S) b. PROJECT NO. Miscellaneous Paper S c. 6b. OTHER REPORT NO(S) (Any other number that may be asalned this report) d. 1. DISTRIBUTION STATEMENT Approved for public release; distribution unlimited. 11. SUPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY Office, Chief of Engineers, U. S. Army Washington, D. C. 13. ABSTRACT This study was conducted for the purpose of developing a relationship between elastic pavement deflection and pavement performance (number of traffic applications necessary to cause failure). Data for the study were taken from past studies of airfield and highway pavements. A summary of test conditions, failure criteria, and traffic type is given for each data source. A relationship was developed between elastic deflection and the number of coverages of traffic for combined airfield and highway data and for airfield data only. The relationship of wheel load and tire pressure is given, and a multiple-regression equation was determined to predict coverages as a function of wheel load, tire pressure, and deflection. DD Noeev O W R 6sACKS JOM "S '473 f OKSOLKTK FOR ARMY USE JAN S. WHICH IS Unclassi t i eca security Claeeificetion

46 Security Unclassified Classification 14. LINK A LINK S LINK C K DeflecionROLE WT ROLE WT ROLE WT De fle ct ion Flexible pavements Traffic tests Unclassified Security Classification

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50 University of T Liino B16 NCEL Romine Street Urbana, Illinois 6181