bazi, briggs, saboundjian, ullidtz 2docs.trb.org/prp/15-3691.pdf · bazi, briggs, saboundjian,...

Paper #15-3691 1 2 3 Seasonal Effects on a Low-Volume Road Flexible Pavement 4 5 6 7 Gabriel Bazi, PhD, PE, Corresponding Author 8 Lebanese American University (LAU) [Current Affiliation] 9 P.O. Box 36, Byblos, Lebanon 10 Dynatest Consulting Inc. [Former Affiliation] 11 165 S. Chestnut St., Ventura, CA 93001 12 Phone: + 1 805 613-7070; Email: [email protected] 13 14 Robert Briggs, PE 15 Dynatest Consulting Inc. 16 13953 US Highway 301 South, Starke, FL USA 32091 17 Tel: +1 904 964 3777 Ext. 225; Email: [email protected] 18 19 Steve Saboundjian, PhD, PE 20 Alaska Department of Transportation and Public Facilities 21 5800 East Tudor Road, Anchorage, AK 99507 22 Phone: +1 907 269-6214; Email: [email protected] 23 24 Per Ullidtz, PhD, Dr.techn. 25 Dynatest International A/S 26 Naverland 32, DK 2600 Glostrup, Denmark 27 Email: [email protected] 28 29 30 31 Paper Submitted for Presentation and Publication at the 94th Annual Meeting of the 32 Transportation Research Board, 2015 33 34 35 36 Word count: 3,502 words text + 15 tables/figures x 250 words (each) = 7,252 words 37 38 39 40 Revision Date: November 14, 2014 41

Bazi, Briggs, Saboundjian, Ullidtz 2

1 ABSTRACT 2 3 Alaska’s Parks Highway is an asphalt paved and predominantly two-lane, low-volume roadway 4 that extends over 323 miles, and links its two largest cities, Anchorage and Fairbanks. This 5 study assessed the effects of thawing on this low-volume roadway pavement and developed 6 seasonal adjustment factors for the different pavement layers. Falling Weight Deflectometer 7 (FWD) testing were carried out weekly at three temperature data probe (TDP) sites during 8 springtime. The purpose of the FWD tests was to monitor the pavement structural conditions and 9 moduli variations during the spring thaw and recovery periods. In addition this work determined 10 when the pavement thaw initiated, how quickly it progressed, and whether the pavement returned 11 to an “equilibrium” summertime state. It was found that profound changes in backcalculated 12 modulus values can occur within one week of the onset of thawing. In addition, moduli were 13 used to develop modular ratios for the subgrade and base course layers. Results showed that 14 during thawing, the subgrade and base course layers reached about 30-40% and 50-70% of their 15 summertime reference moduli, respectively. These ratios are lower than those currently used in 16 Alaskan pavement design. It is recommended to conduct further testing to verify the seasonal 17 adjustment factors proposed in this study. Surface moduli values, calculated and plotted without 18 the need for the pavement layer thicknesses, were found to be useful in instantly identifying 19 whether partial thawing has occurred. 20 21

22 23 24

Keywords: Falling Weight Deflectometer (FWD), Spring thaw, Temperature data probes, 25 Modular ratios, Parks Highway, Low Volume Road (LVR) 26


INTRODUCTION 1 Alaska’s Parks Highway, shown in Figure 1, links the two largest cities of the state and can be 2 characterized as a low-volume road along long stretches of its corridor. It is an interstate, asphalt 3 paved two-lane highway that extends over 323 miles from the Glenn Highway, 35 miles north of 4 Anchorage, to Fairbanks. It is owned and maintained by the Alaska Department of 5 Transportation and Public Facilities (ADOT&PF). It is expected that this highway will be 6 impacted by the potential development of a natural gas pipeline along its corridor. Therefore 7 assessing the health of this corridor’s pavement infrastructure and evaluating layer properties is 8 of utmost importance. 9

The highway traverses two climatic zones: a transitional climate zone from its southern 10 end to Broad Pass [Milepost (MP) 193], and a continental zone north of MP 193. While both 11 zones are considered dry, discontinuous permafrost conditions prevail in the continental zone. 12 The transitional zone is relatively warmer than the continental zone, with temperatures at or 13 above freezing. Within each zone and in the mountainous regions of the Alaska Range, micro 14 climates exist where atypical climatic conditions can prevail (1). 15

Along the highway corridor, ADOT&PF maintains a Road Weather Information System 16 (RWIS) which is a network of cameras, and meteorological and pavement sensors (2). The 17 system includes Temperature Data Probes (TDP) where temperature readings are collected 18 hourly at several depths along 72-inch vertical probes embedded within the roadway 19 embankment and its pavement. The data is used for road design, research, and by road 20 maintenance personnel for winter sanding operations. In-situ characterization of pavement layer 21 properties is therefore an important task that will help assessing the effects of seasonal variations 22 on pavement performance and damage. 23

In the past a number of studies have addressed the effects of seasonal climatic factors on 24 pavement materials and pavement damage. 25

One study monitored and analyzed pavement damage during spring thaw (1). The study 26 used traffic, pavement temperature, and Falling Weight Deflectometer (FWD) data to determine 27 the fraction of overweight axle loads and corresponding pavement damage during spring thaw. 28 Comparisons of remaining life using mechanistic methods were conducted. In addition, ground 29 temperature measurements were also analyzed to determine when thaw initiates and how long 30 spring load restrictions are required. 31

The effects of seasonal freeze–thaw cycles on a Swedish instrumented flexible pavement 32 structure were investigated in 2010 (3) by conducting frequent FWD measurements throughout 33 spring thaw and the recovery periods. Using the backcalculated layer stiffness and moisture 34 measurements in unbound layers, a degree of saturation-based moisture-stiffness model was 35 developed for the granular layer and the subgrade. This model fell on a unique curve showing 36 promising agreement with the laboratory-based model proposed by the mechanistic empirical 37 design guide that analytically predicts changes in modulus due to changes in moisture. 38

Granular base course materials from Alaska were characterized to capture the effects of 39 temperature, freeze–thaw cycle, moisture, and fines contents on its resilient moduli (MR) (4). 40 Predictive MR models were developed and compared with those based on the Long-Term 41 Pavement Performance data. 42

Subgrade soil characterization was carried out in another study from Tennessee (5). The 43 coefficients for the generalized universal MR model were obtained and linked to the soil moisture 44 content and its physical properties. 45


Effects of climatic factors on flexible pavement performance and service life were 1 examined in another study (6). Temperature factors (both the increase in average annual 2 temperature and the seasonal variation in temperature) were examined through a sensitivity 3 analysis. It was concluded that these temperature factors are the most influential in pavement 4 performance, and the pavement service life may experience considerable reduction because of 5 climate change in some regions if design is not adapted to the changed climate. 6

7 OBJECTIVE 8 The main objective of this study was to assess the effects of thawing on this low-volume 9 roadway pavement and develop seasonal adjustment factors (i.e., modular ratios) for the different 10 pavement layers. It also aimed at determining when pavement thaw initiated, how quickly it 11 progressed, and when the pavement returned to an “equilibrium” summertime state. The 12 pavement conditions ranged from fully frozen pavement and subgrade to fully thawed 13 conditions. Pavement layer moduli were determined at three TDP sites and different springtime 14 dates, then trends were analyzed and reported. Of particular interest are the minimum layer 15 moduli during the thaw period for the various layers. This information was used to develop 16 recommendations regarding seasonal pavement layer moduli variations for use in future 17 structural design. 18

19 PAVEMENT TESTING AND DEFLECTION EVALUATION 20 ADOT&PF performed repeated FWD measurements at three TDP sites located along the Parks 21 Highway during thawing and recovery periods. Temperature probes, placed at those sites, have 22 been in use for several years to monitor thawing of the pavement structures and have been the 23 primary source of information used to place and remove SLRs in order to protect the pavement 24 from overloading during its weakest conditions. 25

Pavement deflection measurements were collected by ADOT&PF personnel on 12 dates 26 between March 8 and July 6, 2011 at each of the three TDP locations – Cantwell (MP 211, 27 northernmost), Little Coal Creek (MP 163.2) and Chulitna (MP 117, southernmost). Deflections 28 were acquired during periods ranging from fully frozen to fully thawed pavement conditions. 29 Average annual daily traffic (AADT) at these sites is shown in Table 1. It should be mentioned 30 that the TDP sites do not include sensors that measure pavement moisture levels. Nevertheless, 31 at these locations, springtime saturation of base course is often observed by road maintenance 32 personnel who report water oozing out of existing pavement cracks. 33

The FWD was setup with the small plate (12-in diameter) and nine geophones located at 34 0, 12, 18, 24, 36, 48, 60, 72 and 84-in radial offsets from the center of the plate. Three drops 35 were recorded at each test point. FWD loads ranged from approximately 8,000 to 15,000-lbs 36 depending on the drop height and pavement stiffness at the time of testing. 37

For analytical purposes, the last drop (drop 3) at each test point was evaluated. Drop 38 number 3 was at approximately the same load level for all sites and testing periods. The 39 deflections were normalized to 9,000-lbs. A summary of the average normalized center 40 pavement deflections for each location are shown in Figure 2. Very small deflections, under 1 41 mil for a 9,000-lbs load, were noted when the pavement was fully frozen and they increased to 42 10-12 mils (1 mil = 0.001 inch or 0.0254 mm) when the pavement was fully thawed. The 43 deflections at all three sites were somewhat comparable. The initiation of thawing varied for 44 each site – April 20 for Cantwell, April 12 for Little Coal Creek and March 30 for Chulitna. 45 Because the deflections at the outer sensors were relatively small during the frozen phase, it was 46


at times difficult to obtain valid data (decreasing deflections with increasing distance from the 1 load center). 2

The pavement deflection basins for the various testing dates at the Little Coal Creek site 3 are shown in Figure 3. The plots for the Cantwell and Chulitna sites follow the same trends as 4 the Little Coal Creek site, and therefore they are not presented in this paper. Based on Figures 2 5 and 3, the following observations can be made: 6

o On March 8 (initial FWD testing date), the deflections for all three sites were very 7 small indicating that the subgrade and pavement upper layers were frozen solid. 8

o Significant thawing occurred between March 30 and April 20 at the three sites. 9 o Thawing was occurring from the “top down” as evidenced by the change in the 10

innermost sensors (closest to the load plate) first. 11 o Thawing continued to occur in the subgrade over the majority of the test period as 12

evidenced by changes in the outermost deflection measurements (36 through 84-in 13 from the load plate). 14

o By May 3rd, for Little Coal Creek and Chulitna, subgrade thawing has advanced to the 15 point that it has no further effect on the measured deflections. By contrast, subgrade 16 thawing was still progressing up to the last test date at Cantwell. 17

o For all locations, once the thaw initiated, it progressed rapidly. 18 o Thaw initiation and progression correlated to the locations, i.e., southernmost 19

locations thawed first and progressed more rapidly. 20 21 SURFACE MODULI 22 An effective and efficient method for evaluating the FWD deflections without requiring the 23 pavement layer thicknesses is to calculate and plot the surface moduli at each geophone position. 24 The surface moduli provide an apparent or equivalent stiffness assuming the pavement is 25 composed of a semi-infinite half-space and the stress zone spreads at a 45 degree angle with 26 depth (Figure 4). As such, the pavement response (deflection) recorded at a distance of 60-in 27 from the load is assumed to be the response of a homogeneous mass at a depth of 60-in. 28

The surface moduli are calculated using the Boussinesq equations. The surface modulus 29 at the center of the load plate is calculated using the distributed load equation: 30

31

E0= 2P�1-μ2�πad0

(1) 32

33 The surface modulus at a distance r from the center of the load plate is calculated using 34

the point load equation: 35 36

Er=P�1-μ2�πrdr

(2) 37

38 Where: 39

E0, Er = Surface modulus, psi 40 P = applied load, lbs 41 µ = Poisson's ratio (assumed to be 0.35) 42 a = Radius of the applied load, in 43 d0 = Deflection at the center of the applied load, in 44


r = distance from the center of the applied load, in 1 dr = deflection at distance r from the center of the applied load, in 2

3 The surface moduli plots for the various testing dates at the three sites are shown in 4

Figures 5 through 7. Notes are provided on the first figure to facilitate interpretation. Inspection 5 of the surface moduli plots showed that: 6

o Pavements in their frozen state exhibited very high stiffnesses. Subgrade stiffnesses 7 could exceed 300 to 400 ksi. 8

o Overall pavement stiffness (SM0) in the frozen state could exceed 2,000 ksi. 9 o The surface moduli plots verified the trend of top down thawing. 10 o It was apparent that the subgrade modulus at Cantwell was still in a state of change on the 11

last test date of July 5. 12 o By May 3rd, the subgrade stiffness had stabilized for Little Coal Creek and Chulitna. 13 o Surface moduli plots can be very effective in determining the state of thaw in the 14

pavement structure. 15 16 LAYER MODULI AND MODULAR RATIOS 17 All layer moduli were backcalculated for each deflection basin using the Dynatest ELMOD 18 software (7). The actual in-situ material properties are derived through a reverse, layered analysis 19 technique using the Odemark-Boussinesq Deflection Basin Fit option. It should be noted that, in 20 general, most of the measured magnitudes of deflection are due to the response of the subgrade. 21 It is therefore very important that the subgrade modulus is accurately determined. A small error 22 in the subgrade modulus will lead to large errors in all layer moduli. 23

The pavement layer thicknesses used during backcalculation were obtained using ground 24 penetrating radar (GPR) testing and verified using coring (Table 1). 25

During the fully frozen state, the pavement materials exhibited very high modulus values 26 which are considered to be unreliable, especially for the base layer. The average layer moduli 27 were restricted to 10,000 ksi, since any higher number would be unrealistic. The average layer 28 moduli for the various testing dates at the Chulitna site are shown in Figure 8 along with the 29 average air and surface temperatures. The plots for the Cantwell and Little Coal Creek sites 30 follow the same trends as the Chulitna site, and therefore they are not presented in this paper. 31 Inspection of the layer moduli plots showed that: 32

o Profound changes in the modulus values occurred within one week of the onset of 33 thawing. 34

o Unbound materials, after thawing, reached minimum values over time followed by a 35 recovery period in which the moduli increased substantially. This minimum occurred 36 shortly after thaw progression and was probably due to trapped moisture above the 37 thaw line. 38

o The thawing process took roughly 20 days to complete at Chulitna and Little Coal 39 Creek. Cantwell occurred later but completed largely in one week. 40

o The modulus values in the frozen state are extremely far above those suggested by the 41 Alaska Flexible Pavement Design (AKFPD) for all material types (8). 42

o The modulus values in the thawed state are lower than those suggested by the 43 AKFPD Guide for all material types. 44

The modular ratios with respect to the July FWD testing (considered as reference 45 conditions) were calculated and plotted in Figures 9 through 11 for the subgrade, base and 46


asphalt concrete layers, respectively. During thawing, the subgrade and base reached about 30-1 40% and 50-70% of the summertime reference moduli, respectively. Currently the AKFPD 2 Guide (8) uses modular adjustments of 50-70% for subgrades, and 70-90% for aggregate base 3 materials. 4 5 TEMPERATURE DATA PROBES (TDP) THAW DEPTH 6 The ADOT&PF RWIS system was used to obtain the air and pavement temperatures from the 7 TDPs for the three sites during FWD testing. Each probe is made up of 16 thermistors; where 8 temperatures are recorded at the pavement surface, just under the pavement, every 3-in for the 9 first foot, and every 6-in for the next five feet as shown in Figure 12. Table 2 shows the Little 10 Coal Creek (MP 163.2) TDP data. The heavy black lines in the table indicate the location of the 11 thaw line (32°F transition). The temperature values are color coded to facilitate interpretation, 12 where higher than freezing temperatures are highlighted in red and lower temperatures are 13 highlighted in blue. Data that was questionable or absent is marked with “NA” for “not 14 available” or replaced with data from the closest available date. 15

The air temperature data is suspect since it does not correlate well with the temperatures 16 measured in the pavement structure. The subgrade was thawed beyond a depth of 72-in around 17 mid-June for the Cantwell (MP 211) site, around May 10 for the Little Coal Creek (MP 163.2) 18 site and around May 17 for Chulitna (MP 117) site. It should be noted that although Chulitna is 19 the southernmost of the three TDP stations, it was not the quickest to thaw. Most likely it does 20 not receive as much daily sunlight as the others. 21 The thaw line was accounted for in ELMOD by using an automatically calculated depth 22 to rigid layer (bedrock). This parameter was enabled during the backcalculation process to 23 compensate for the fact that the subgrade is partially frozen. It removes the masking effect of the 24 stiff frozen portion of the subgrade and therefore improves the accuracy of backcalculation 25 process for the upper pavement layers. 26 Figure 13 shows the TDP thaw depth, average depth to rigid layer from backcalculation, 27 and average FWD center deflections and deflections at 72-in. Close relationship exists between 28 the outermost deflections, the TDP depth of thaw and the calculated depth to bedrock after 29 thawing. This illustrates that the outermost deflections are heavily influenced by the frozen layer 30 at depths of at least 72-in or less. 31 32 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS 33 This study revealed that the FWD is an excellent nondestructive tool to evaluate thawing 34 conditions, and quantify seasonal effects on this low-volume roadway. The procedure outlined 35 in this study is not only of value to Alaskan highways, but anywhere where springtime pavement 36 weakening occurs. Without any knowledge of pavement layer types and thicknesses, the 37 operator of a FWD can, immediately, identify points where partial thawing has occurred, by 38 examining the surface moduli plot on the screen, and pinpointing an approximate thaw depth. 39 This information can be communicated in real time for the application of load restrictions. 40 Likewise, the operator can determine the recovery, although this might require the use of some 41 historical data. 42

FWD testing on the Parks Highway flexible pavement at three TDP sites showed that 43 pavement deflections are negligible under a 9,000-lbs load when the pavement is in its frozen 44 state. The pavement deflections increased dramatically as the pavement structure began to thaw. 45


The outer sensors are particularly suited to detect where the thaw line is located within the 1 pavement structure. 2

When the thaw initiated, it progressed rapidly downward reaching the 72-in limit of the 3 TDPs within a week or two. The surface moduli plot is a useful tool in quickly assessing the 4 depth of the thaw line as is the “Depth to Bedrock” calculation routine in ELMOD. The 5 deflection basin shapes correlated well with the TDP temperature data. 6

The current round of testing was completed early July. There is evidence that the 7 pavement sections were still undergoing thawing in the lower subgrade layers and that the 8 subgrade and other unbound layers were undergoing recovery, most likely due to the drying 9 process. It is recommended that another round of testing be conducted through fall and into the 10 winter to establish equilibrium conditions and to investigate the effects of freezing on the 11 pavement structures. 12

Seasonal adjustment factors were developed for this low-roadway roadway; Figures 9 13 through 11 show these modular ratios for the different pavement layers. Lower than the 14 currently used by the ADOT&PF modular ratios are recommended: 50-70% and 30-40% for 15 unbound base course and subgrade, respectively. Further testing should be conducted to verify 16 the seasonal adjustment factors proposed in this paper since they differ from those currently used 17 by the AKFPD Guide. The methodology described in this study can be applied to other TDP 18 sites, along other highway corridors within the state to validate the universality of the layer 19 adjustment factors derived in this study. Temperature and frequency sweep laboratory stiffness 20 testing is recommended for the typical asphalt concrete mixes to determine the seasonal 21 variations. 22 23 ACKNOWLEDGMENTS 24 The work represented herein was the result of a team effort. The authors would like to thank 25 ADOT&PF personnel for collecting the FWD test data over several weeks. 26 27 DISCLAIMER 28 The contents of this paper reflect the views of the authors, who are responsible for the accuracy 29 of the data presented herein. The paper’s contents do not necessarily reflect the views or policies 30 of Alaska DOT&PF or any local sponsor. This work does not constitute a standard, 31 specification, or regulation. Alaska DOT&PF does not endorse, support or favor any product, 32 equipment, technology, software or procedure cited in this paper. 33 34 REFERENCES 35 1. Raad, L., E. Johnson, D. Bush, and S. Saboundjian. Parks Highway Load Restriction Field 36

Data Analysis Case Study. In Transportation Research Record: Journal of the 37 Transportation Research Board, No. 1615, Transportation Research Board of the National 38 Academies, Washington, D.C., 1998, pp. 32-40. 39 40

2. Alaska Department of Transportation & Public Facilities. Road Weather Information System 41 (RWIS). http://www.dot.state.ak.us/iways/roadweather/forms/IndexForm.html. Accessed 42 July 30, 2014. 43

44


3. Salour, F., and S. Erlingsson. Investigation of a Pavement Structural Behaviour during 1 Spring Thaw using Falling Weight Deflectometer. Road Materials and Pavement Design, 2 Volume 14, Issue 1, 2013, pp. 141-158. 3

4 4. Li, L., J. Liu, X. Zhang, and S. Saboundjian. Resilient Modulus Characterization of Alaska 5

Granular Base Materials. In Transportation Research Record: Journal of the Transportation 6 Research Board, No. 2232, Transportation Research Board of the National Academies, 7 Washington, D.C., 2011, pp. 44-54. 8

9 5. Zhou, C., B. Huang, E. C. Drumm, X. Shu, Q. Dong, and S. Udeh. Seasonal Resilient 10

Modulus Inputs for Tennessee Soils and Their Effects on Asphalt Pavement Performance. 11 Proceedings of the 2013 Transportation Research Board Annual Meeting, Paper #13-4351. 12

13 6. Qiao, Y., G. W. Flintsch, A. R. Dawson, and T. Parry. Examining Effects of Climatic 14

Factors on Flexible Pavement Performance and Service Life. In Transportation Research 15 Record: Journal of the Transportation Research Board, No. 2349, Transportation Research 16 Board of the National Academies, Washington, D.C., 2013, pp. 100-107. 17

18 7. Evaluation of Layer Moduli and Overlay Design (ELMOD) Software, version 6.1.75. 19

Dynatest International, Naverland 32, DK - 2600 Glostrup, Denmark. 20 21

8. Alaska Flexible Pavement Design Guide, Report No. FHWA-AK-RD-03-01, ADOT&PF, 22 April 2004. 23


LIST OF TABLES 1 2 TABLE 1 AADT and Pavement Layer Thicknesses 3

TABLE 2 Little Coal Creek MP 163.2 Temperature Probe Data 4 5 6 7 LIST OF FIGURES 8 9 FIGURE 1 Parks Highway, northbound at MP 162. 10 FIGURE 2 Normalized center deflections at 9,000-lbs. 11 FIGURE 3 Little Coal Creek MP 163.2 normalized deflections (at 9,000-lbs) vs. radial distance. 12 FIGURE 4 Surface moduli concept. 13 FIGURE 5 Cantwell MP 211 surface moduli vs. radial distance. 14 FIGURE 6 Little Coal Creek MP 163.2 surface moduli vs. radial distance. 15 FIGURE 7 Chulitna MP 117 surface moduli vs. radial distance. 16 FIGURE 8 Chulitna MP 117 layer moduli. 17 FIGURE 9 Subgrade modular ratios (July reference). 18 FIGURE 10 Base modular ratios 19 FIGURE 11 Asphalt concrete modular ratios 20 FIGURE 12 Temperature data probes locations (2). 21 FIGURE 13 Little Coal Creek MP 163.2 thaw depth and deflection vs. date. 22


TABLE 1 AADT and Pavement Layer Thicknesses 1 Location [MP] AADT Per Lane,

2011 Layer Thicknesses Used in ELMOD

Cantwell [MP 211] 687 4-in Asphalt Concrete over 11-in Base over Subgrade Little Coal Creek [MP 163.2] 641 6-in Asphalt Concrete over 4.5-in Base over Subgrade

Chulitna [MP 117] 583 4-in Asphalt Concrete over 17-in Base over Subgrade 2 TABLE 2 Little Coal Creek MP 163.2 Temperature Probe Data 3

4 5

6 FIGURE 1 Parks Highway, northbound at MP 162. 7 8

Month/Day 03/08 03/16 03/23 03/30 04/12 04/20 04/26 05/03 05/10 05/17 06/01 07/15Air NA NA 25.6 34.2 31.8 32.5 39.8 38 37.2 46.1 54.3 59.7

Surface NA NA 28.4 38.8 50 48.5 56.6 60.1 59.7 68.5 73.6 81.3Bottom NA NA 26.6 34.6 43 42.5 50.9 53.4 52 61.5 69.6 74.8

3" NA NA 25.7 32.7 38.1 41.1 47.7 51.8 52.1 58.6 68.9 72.26" NA NA 25 31.4 34.2 40.1 45.6 50.4 51.9 56.8 68.3 70.39" NA NA 24.4 30.8 31.8 38.8 43.9 49 51.3 55.2 67.4 68.6

12" NA NA 23.9 30.4 31.6 37.6 42.4 47.5 50.5 53.9 66.5 67.418" NA NA 22.9 29.3 31.1 35.3 40 44.7 48.6 51.5 64.4 65.624" NA NA 22.7 28.9 31.2 33.4 38.3 42.7 47 49.7 62.6 64.530" NA NA 22.2 28.2 30.8 32.1 36.1 40.4 45 47.6 59.8 63.236" NA NA 21.9 27.5 30.7 31.8 34.2 38.6 43.2 45.6 57.4 62.142" NA NA 22 27.2 30.6 31.6 32.4 37.2 41.6 44 55.1 61.248" NA NA 22.3 27.1 30.6 31.3 32.2 35.8 39.7 42 52.5 59.754" NA NA 22.9 27.1 30.6 31.2 32 34.2 37.3 39.6 49.3 58.360" NA NA 23.8 27.2 30.6 31.4 31.9 33 35.4 37.6 46.8 5766" NA NA 24.9 27.7 30.7 31.4 32.2 32 33.7 35.7 44.2 55.672" NA NA 26.2 28.5 31.1 31.7 32.3 32 33.3 34 41.9 54.1


1 FIGURE 2 Normalized center deflections at 9,000-lbs. 2 3

4 FIGURE 3 Little Coal Creek MP 163.2 normalized deflections (at 9,000-lbs) vs. radial 5 distance. 6 7


1 FIGURE 4 Surface moduli concept. 2

3 4 FIGURE 5 Cantwell MP 211 surface moduli vs. radial distance. 5 6

Surface modulus at 0” (SM0) assumes everything below 0” is uniform

SM60 assumes everything below 60” is uniform

60”

Pavement upper layers and subgrade thawed

Upper layers thawing

Subgrade thawing

Pavement upper layers and subgrade frozen


1 FIGURE 6 Little Coal Creek MP 163.2 surface moduli vs. radial distance. 2 3

4 FIGURE 7 Chulitna MP 117 surface moduli vs. radial distance. 5 6


1

2 FIGURE 8 Chulitna MP 117 layer moduli. 3 4

5 FIGURE 9 Subgrade modular ratios (July reference). 6 7


1 FIGURE 10 Base modular ratios (July reference). 2 3

4 FIGURE 11 Asphalt concrete modular ratios (July reference). 5 6


1 FIGURE 12 Temperature data probes locations (2). 2 3

4


1 FIGURE 13 Little Coal Creek MP 163.2 thaw depth and deflection vs. date. 2

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