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4Design of SPS-1 and SPS-2 Experiments The SPS-1 experiment was designed to assess the influence of the following factors on the performance of AC pavements: ⢠AC thickness, ⢠Base type, ⢠Base thickness, ⢠Subdrainage, ⢠Climate, ⢠Subgrade, and ⢠Truck traffic level. The original experimental design and research plan for SPS-1 is described in a Strategic Highway Research Program (SHRP) report (17). The design factorial for the SPS-1 exper- iment is shown in Table 1. The first two digits of the number shown within each cell signify the SPS experiment (in this case, SPS-1); the last two digits signify the test section num- ber of each design. The originally intended site factorial for the SPS-1 experi- ment is shown in Table 2. The states listed in the upper row for each subgrade type are those that built designs 0101 through 0112. The states listed in the lower row for each subgrade type are those that built designs 0113 through 0124. In the wet-freeze-fine subgrade cells, two pairs of states are listed; each state was to build a set of the 12 designs, so as to create âreplicatesâ of the designs. These are not, however, replicates in the true sense of the word, as the sites are not identical in terms of truck traffic or climate. The Texas site, originally listed in the dry-nonfreeze-coarse subgrade cell, was found to have a fine subgrade; conse- quently, it was recategorized as a dry-nonfreeze-fine site, as shown in the actual site factorial (Table 3). The pavement designs corresponding to designs 0101 through 0112 are shown in Table 4; those for designs 0113 through 0124 are shown in Table 5. The SPS-2 experiment was designed to assess the influence of the following factors on the performance of jointed PCC pavements: ⢠PCC thickness, ⢠Concrete flexural strength, ⢠Base type, ⢠Lane width, ⢠Subdrainage, ⢠Climate, ⢠Subgrade, and ⢠Truck traffic level. The original experimental design and research plan for SPS-2 are described in a SHRP report (18). The design facto- rial for the SPS-2 experiment is shown in Table 6. The first two digits of the number within each cell in Table 6 signify the SPS-2 experiment, and the last two digits signify the test sec- tion design. The site factorial for the SPS-2 experiment is shown in Table 7. The upper row corresponding to each subgrade type lists the states that built designs 0201 through 0212; the pave- ment designs constructed at these sites are shown in Table 8. The bottom row associated with each subgrade type in the table lists the states that built designs 0213 through 0224; the corresponding pavement designs are shown in Table 9. Several of the state DOTs also constructed supplemental test sections to evaluate design features or materials typically used in the state or that were of interest for future use. A total of 32 supplemental test sections were built at SPS-1 sites; 40 supplemental sections were built at SPS-2 sites. SPS-1 and SPS-2 Locations The locations of the SPS-1 sites and the SPS-2 sites are shown in Figures 1 and 2, and location details for the SPS-1 and SPS-2 sites are given in Tables 10 and 11. A comparison C H A P T E R 2 Description of the SPS-1 and SPS-2 Experiments
5Total Base Thickness (in.) Surface Thickness (in.) Dense- Graded Aggregate Asphalt- Treate d Base Asphalt- Treated Base over Dense- Graded Aggregate Perm eable Asphalt-Treated Base over Aggregate Asphalt- Treated Base ove r Perm eable Asphalt- Treated Base 4 0113 0103 0105 0107 0122 8 7 0101 0115 0117 0119 0110 4 0102 0116 0118 0120 0111 12 7 0114 0104 0106 0108 0123 4 0121 0112 16 7 0109 0124 Drainage No Yes Base Type Wet Dry Freeze Nonfreeze Freeze Nonfreeze IA, OH AL KS NM Fine subgrade VA, MI LA NE OK DE FL NV TX Coarse subgrade WI AR MT AZ Wet Dry Freeze Nonfreeze Freeze Nonfreeze IA, OH AL KS NM Fine subgrade VA, MI LA NE OK, TX DE FL NV Coarse subgrade WI AR MT AZ Table 1. SPS-1 design factorial. Table 2. Intended SPS-1 site factorial. Table 3. Actual SPS-1 site factorial.
6Drainage No Yes Base Type Total Base Thickness (in.) Surface Thickness (in.) Dense- Graded Aggregate Asphalt- Treate d Base Asphalt- Treated Base over Dense- Graded Aggregate Perm eable Asphalt-Treated Base over Aggregate Asphalt- Treated Base ove r Perm eable Asphalt- Treated Base 4 0103 0105 0107 8 7 0101 0110 4 0102 0111 12 7 0104 0106 0108 4 0112 16 7 0109 Table 4. Core SPS-1 test sections built at the Alabama, Delaware, Florida, Iowa, Kansas, Nevada, New Mexico, and Ohio sites. Total Base Thickness (in.) Surface Thickness (in.) Dense- Graded Aggregate Asphalt- Treate d Base Asphalt- Treated Base over Dense- Graded Aggregate Perm eable Asphalt-Treated Base over Aggregate Asphalt- Treated Base ove r Perm eable Asphalt- Treated Base 4 0113 0122 8 7 0115 0117 0119 4 0116 0118 0120 12 7 0114 0123 4 0121 16 7 0124 Drainage No Yes Base Type Table 5. Core SPS-1 test sections built at the Arizona, Arkansas, Louisiana, Michigan, Montana, Nebraska, Oklahoma, Texas, Virginia, and Wisconsin sites.
7Drainage No Ye s Base type Slab Thickness (in.) Flexural Strength (psi) Lane Width (ft ) Aggregate Lean Concrete Base Perm eable Asphalt- Treated Base 12 0201 0205 0209 550 14 0213 0217 0221 12 0214 0218 0222 8 900 14 0202 0206 0210 12 0215 0219 0223 550 14 0203 0207 0211 12 0204 0208 0212 11 900 14 0216 0220 0224 Wet Dry Freeze Nonfreeze Freeze Nonfreeze OH, KS NCFine subgrade MI, IA, ND AR DE NV, WA CACoarse subgrade WI CO AZ Table 6. SPS-2 design factorial. Table 7. SPS-2 site factorial. Drainage No Yes Base type Slab Thickness (in.) Flexural Strength (psi) Lane Width (ft ) Aggregate Lean Concrete Base Permeable Asphalt- Treated Base 12 0201 0205 0209 550 14 12 8 900 14 0202 0206 0210 12 550 14 0203 0207 0211 12 0204 0208 0212 11 900 14 Table 8. Core SPS-2 test sections built at California, Delaware, Kansas, Nevada, North Carolina, Ohio, and Washington sites.
8Drainage No Yes Base type Slab Thickness (in.) Flexural Strength (psi) Lane Width (ft ) Aggregate Lean Concrete Base Permeable Asphalt- Treated Base 12 550 14 0213 0217 0221 12 0214 0218 0222 8 900 14 12 0215 0219 0223 550 14 12 11 900 14 0216 0220 0224 Table 9. Core SPS-2 test sections built at Arizona, Arkansas, Colorado, Iowa, Michigan, North Dakota, and Wisconsin sites. Copyright © 1988-2004 Microsoft Corp. and/or its suppliers. All rights reserved. http://www.microsoft.com/streets/ © Copyright 2003 by Geographic Data Technology, Inc. All rights reserved. © 2004 NAVTEQ. All rights reserved. This data includes information taken with permission from Canadian authorities © Her Majesty the Queen in Right of Canada. (See www.microsoft.com/about/legal/permissions/faq.mspx) 0 mi 200 400 600 800 1000 Figure 1. SPS-1 (flexible pavement) sites.
9Copyright © 1988-2004 Microsoft Corp. and/or its suppliers. All rights reserved. http://www.microsoft.com/streets/ © Copyright 2003 by Geographic Data Technology, Inc. All rights reserved. © 2004 NAVTEQ. All rights reserved. This data includes information taken with permission from Canadian authorities © Her Majesty the Queen in Right of Canada. (See www.microsoft.com/about/legal/permissions/faq.mspx) 0 mi 200 400 600 80 0 1000 Figure 2. SPS-2 (rigid pavement) sites. SHRP ID State County or Parish Nearby City or Town Rout e L atitude Longitude 010100 AL Lee Opelik a U S 280 32.61 85.25 040100 AZ Mohave Kingman US 93 35.39 114.26 050100 AR Craighead Jonesboro US 63 35.72 90.58 100100 DE Sussex Ellendale US 113 38.79 75.44 120100 FL Palm Beach Coral Springs US 27 26.54 80.69 190100 IA Lee Burlington US 61 40.70 91.25 200100 KS Kiow a G reensburg US 54 37.60 99.25 220100 LA Calcasieu Lake Charles US 171 30.33 93.20 260100 MI Clinton Lansing US 27 42.99 84.52 300100 MT Cascad e G reat Falls I-15 47.41 111.53 310100 NE Thayer Hebron US 81 40.07 97.62 320100 NV Lande r B attle Mountain I-80 40.69 117.01 350100 NM Doña Ana Las Cruces I-25 32.68 107.07 390100 OH Delawar e D elaware US 23 40.43 83.06 400100 OK Comanche Lawton US 62 34.64 98.66 480100 TX Hidalg o M cAllen US 281 26.74 98.11 510100 VA Pittsylvani a D anville US 29 36.66 79.37 550100 WI Marathon Wausau SR 29 44.87 89.29 Table 10. SPS-1 location data.
of Figures 1 and 2 shows that the sites in the two experiments are comparably distributed in the eastern, midwestern, and western regions of the country; in the southeastern region, however, there are four SPS-1 sites but no SPS-2 sites. SPS-1 and SPS-2 Climates The average annual precipitation and the average annual temperature for each of the SPS-1 and SPS-2 sites are shown in Tables 12 and 13, respectively. This information was obtained from âvirtual weather stationâ statistics in the LTPP database, which represent distance-weighted averages from as many as five operating weather stations in the vicinity of each site. The distribution of the SPS-1 and SPS-2 sites with respect to average annual precipitation and temperature is illustrated in Figure 3. The Thornthwaite moisture index can be used to describe a locationâs climate in a way that reflects both precipitation and temperature (19). This index is calculated as a function of the difference between the average monthly precipitation and the potential evapotranspiration in each month of the year, with evapotranspiration being a function of the aver- age monthly temperature, the number of days in the month, and the length of the day (the number of hours between sunrise and sunset) in the middle of each month. The Thornthwaite moisture index values calculated for the 10 SHRP ID State County or Parish Nearby City or Town Route Latitude (deg) Longitude (deg) 040200 AZ Maricopa Phoenix I-10 33.45 112.74 050200 AR Saline Benton I-30 34.54 92.68 060200 CA Merced Turlock SR 99 37.42 120.77 080200 CO Adams Denver I-76 39.97 104.79 100200 DE Sussex Ellendale US 113 38.87 75.44 190200 IA Polk Des Moines US 65 41.65 93.47 200200 KS Dickenson Salina I-70 38.97 97.09 260200 MI Monroe Toledo, Ohio US 23 41.75 83.70 320200 NV Lander Battle Mountain I-80 40.72 117.04 370200 NC Davidson Lexington US 52 35.87 80.27 380200 ND Cass Fargo I-94 46.88 97.17 390200 OH Delaware Delaware US 23 40.43 83.08 530200 WA Adams Ritzville US 395 47.06 118.42 550200 WI Marathon Wausau SR 29 44.83 89.23 State State Code Latitude (degrees ) Longitude (degrees ) Average Annual Precipitatio n (in.) Average Annual Temperature AL 01 32.61 85.25 51.5 63.2 AZ 04 35.39 114.26 8.1 66.5 AR 05 35.72 90.58 48.1 60.1 DE 10 38.79 75.44 45.3 55.6 FL 12 26.33 80.69 52.5 73.5 IA 19 40.70 91.25 39.2 52.0 KS 20 37.60 99.25 25.0 55.1 LA 22 30.33 93.20 59.8 68.0 MI 26 42.99 84.52 31.7 47.8 MT 30 47.41 111.53 14.2 44.8 NE 31 40.07 97.62 29.5 52.5 NV 32 40.69 117.01 9.0 49.7 NM 35 32.68 107.07 10.6 60.4 OH 39 40.43 83.06 38.3 50.2 OK 40 34.64 98.66 30.7 61.7 TX 48 26.74 98.11 22.1 54.9 VA 51 36.66 79.37 44.2 57.5 WI 55 44.87 89.29 32.1 42.6 (°F) Table 11. SPS-2 location data. Table 12. Average annual precipitation and temperature levels for SPS-1 sites.
SPS-1 and SPS-2 sites are shown in Tables 14 and 15, listed from most arid (negative numbers) to most humid (positive numbers). In Figure 3, the SPS-1 and SPS-2 sites whose precipitation and temperature levels plot in the upper left-hand corner (high average annual temperature and low average annual precipitation) are those with the lowest Thornthwaite mois- ture index values. The Arizona SPS-2 site is the most arid of all of the sites, with a moisture deficit (potential evapotran- spiration exceeding precipitation) in every month of the year, and a Thornthwaite moisture index of -51. The average monthly precipitation and average monthly minimum, 11 State State Code Latitude (deg) Longitude (deg) (°F) Average Annual Precipitatio n (in.) Average Annual Temperature AZ 04 33.45 112.74 7.6 71.4 AR 05 34.54 92.68 53.0 61.7 CA 06 37.42 120.77 11.9 61.8 CO 08 39.97 104.79 14.7 49.7 DE 10 38.87 75.44 45.4 55.7 IA 19 41.65 93.47 33.1 48.9 KS 20 38.97 97.09 31.9 54.9 MI 26 41.75 83.70 33.0 49.9 NV 32 40.72 117.04 8.9 49.7 NC 37 35.87 80.27 44.2 58.6 ND 38 46.88 97.17 22.3 41.3 OH 39 40.43 83.06 38.3 50.2 WA 53 47.06 118.42 10.8 49.1 WI 55 44.83 89.23 32.1 42.7 Table 13. Average annual precipitation and temperature levels for SPS-2 sites. 40 52 64 76 AZ 02 CA 02 CO 02 WA 02 MT 01 NV 02 NV 01 AZ 01 NM 01 TX 01 KS 01 OK 01 FL 01 LA 01 AL 01 DE 01 DE 02 NE 01 IA 01 MI 01 WI 01 WI 02ND 02 IA 02 OH 02 AR 02 AR 01 VA 01 NC 02 OK 02 MI 02 OH 01 0 21 42 63 Average annual precipitation (in) A ve ra ge a nn ua l t em pe ra tu re (d eg F) Figure 3. Distribution of average annual precipitation and temperature at SPS-1 and SPS-2 sites.
mean, and maximum temperatures at the Arizona SPS-2 site are shown in Figure 4. By comparison, the site where the Nevada SPS-1 and SPS-2 test sections are located receives only slightly more precipita- tion than the Arizona SPS-2 site, but it has a higher Thorn- thwaite moisture index (-23). The Nevada site has a moisture surplus in 6 months of the year and a moisture deficit in the other 6 months. At 4,500 ft above sea level, the Nevada site has much lower temperatures than the Arizona SPS-2 site, which sits at 1,100 ft above sea level. The average monthly precipitation and the average monthly minimum, mean, and maximum temperatures at the Nevada SPS-1 and SPS-2 site are plotted in Figure 5. 12 State State Code TMI AZ 04 -48 NM 35 -39 NV 32 -23 OK 40 -2 KS 20 3 FL 12 3 TX 48 4 MT 30 13 NE 31 23 LA 22 38 AL 01 51 AR 05 56 VA 51 62 IA 19 64 MI 26 73 DE 10 79 OH 39 87 WI 55 106 State State Code TMI AZ 04 -51 CA 06 -32 NV 32 -23 WA 53 -10 CO 08 -5 KS 20 21 ND 38 36 IA 19 53 NC 37 56 AR 05 61 MI 26 61 DE 10 78 OH 39 87 WI 55 105 Table 14. Thornthwaite moisture index (TMI) values for SPS-1 sites. Table 15. Thornthwaite moisture index (TMI) values for SPS-2 sites. Arizona SPS-2 0 10 20 30 40 50 60 70 80 90 100 110 120 1 2 3 4 5 6 7 8 9 10 11 12 13 Month Te m pe ra tu re (d eg F) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Pr ec ip ita tio n (in ) min temp mean temp max temp precip Figure 4. Monthly average precipitation and high, mean, and low temperatures at the Arizona SPS-2 site.
In general, the Thornthwaite moisture index values at the SPS-1 and SPS-2 sites increase with increasing average annual precipitation and decreasing average annual temperature, as shown as a diagonal line downward and to the right across the plot in Figure 3. The site with the highest Thornthwaite mois- ture index value is not the one with the highest average annual precipitation (Louisiana SPS-1), but rather the site closest to the lower right-hand corner of the plot (the Wisconsin SPS-1 and SPS-2 test sections). Although there are several other sites that receive more precipitation, the combi- nation of moderate precipitation and low temperatures at the Wisconsin site results in a moisture surplus in 11 of 12 months of the year and a Thornthwaite moisture index of 105. A plot of the average monthly precipitation and average monthly minimum, mean, and maximum temperatures at the Wisconsin SPS-1 and SPS-2 site is shown in Figure 6. In the design of a pavement subsurface drainage system, a locationâs precipitation is typically characterized by a design rainfall (also called a design storm), which is the amount of rainfall expected with a selected frequency and duration. The frequency (also called the return period) is the likelihood of that event occurring in any given year. A 100-year storm, for example, is an event that has a 1% chance of occurrence in any given year. A 1-year rainfall is considered a once-a-year eventâthat is, with a 100% chance of occurrence in any given year. Thus a 1-year, 1-hour rainfall is an amount of rainfall that, at a particular location, lasts 1 hour and occurs, on average, once a year. A 2-year, 1-hour rainfall is an amount of rainfall that lasts 1 hour and occurs, on average, once every 2 years. As shown in Figure 7, there is an evident, albeit nonlinear, correlation between average annual precipitation and the 1-year, 1-hour rainfall for nearly all of the sites. The excep- tions are the three SPS-1 sites closest to the Gulf Coast (Texas, Louisiana, and Florida), for which the correlation curve seems to be shifted upward (higher 1-year, 1-hour rainfall at those sites than for noncoastal sites with similar levels of average annual precipitation). In the FHWA report Highway Subdrainage Design, Moul- ton cited Cedergren as having recommended 1-year, 1-hour precipitation rates as the basis for computing infiltration rates into pavement structures (1, 20). The contour map that Cedergren recommended for this purpose was from the 1961 Rainfall Frequency Atlas of the United States (21), which has been superseded in part by other reports (22-24). In contrast, the reference manual for the National Highway Instituteâs training course on pavement subsurface drainage design says that âa storm of 2-year frequency and 1-hour 13 Nevada SPS-1 and SPS-2 min temp mean temp max temp precip 0 10 20 30 40 50 60 70 80 90 100 110 120 1 2 3 4 5 6 7 8 9 10 11 12 13 Month Te m pe ra tu re (d eg F) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Pr ec ip ita tio n (in ) Figure 5. Monthly average precipitation and high, mean, and low temperatures at the Nevada SPS-1 and SPS-2 site.
14 Wisconsin SPS-1 and SPS-2 min temp mean temp max temp precip 0 10 20 30 40 50 60 70 80 90 100 110 120 1 2 3 4 5 6 7 8 9 10 11 12 13 Month Te m pe ra tu re (d eg F) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 Pr ec ip ita tio n (in ) Figure 6. Monthly average precipitation and high, mean, and low temperatures at the Wisconsin SPS-1 and SPS-2 site. 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 0 5 10 15 20 25 30 35 40 45 50 55 60 65 Average annual precipitation, inches O ne -y ea r, on e- ho ur pr ec ip ita tio n, in ch es Gulf SPS-1 sites (FL, LA, TX) All other SPS-1 and SPS-2 sites Figure 7. One-year, 1-hour precipitation rate versus average annual precipitation for SPS-1 and SPS-2 sites.
duration is typically used in design to determine the amount of rainfall that will be available to infiltrate the pavementâ (8). In any case, if the 1-year, 1-hour precipitation amount or the 2-year, 1-hour precipitation amount is known for a given location, it is not difficult to determine the other amount using the contour maps in the publications mentioned above. In addition, precipitation frequency data for weather stations in some states are accessible in electronic form. For example, there are Web sites that, once you enter the latitude and lon- gitude for any point within one of those states, will provide precipitation levels for a range of durations and frequencies. Such precipitation data was collected for the eight SPS-1 and SPS-2 sites located within those states; the results are pre- sented in Tables 16 and 17 and Figure 8. There is a strong curvilinear correlation between the 1-year, 1-hour precipita- tion levels and the 2-year, 1-hour precipitation levels. There is no right answer as to which rainfall frequency is most appropriate for use in pavement subsurface drainage design. What is important is that an agency pick a design rainfall, use it consistently in design, and then document the design rainfall used, along with other details of the drainage system design. 15 State State Code One-Year, 1-hour Rainfall (in./h) Two-Year, 1-Hour Rainfall (in./h) AL 01 1.7 AZ 04 0.5 0.8 AR 05 1.4 DE 10 1.4 FL 12 2.3 IA 19 1.3 KS 20 1.3 LA 22 2.2 MI 26 1.1 MT 30 0.4 NE 31 1.4 NV 32 0.25 0.32 NM 35 0.6 0.85 OH 39 1.0 1.32 OK 40 1.4 TX 48 1.9 VA 51 1.2 1.48 WI 55 1.2 State State Code One-Year, 1-Hour Rainfall (in./h) Two-Year, 1-Hour Rainfall (in./h) AZ 04 0.6 0.79 AR 05 1.6 CA 06 0.5 CO 08 0.6 DE 10 1.4 IA 19 1.3 KS 20 1.4 MI 26 1.1 NV 32 0.25 0.32 NC 37 1.3 1.60 ND 38 1.0 OH 39 1.0 1.32 WA 53 0.3 WI 55 1.2 Table 16. One-year and 2-year 1-hour rainfalls for SPS-1 sites. Table 17. One-year and 2-year 1-hour rainfalls for SPS-2 sites.
Test Section Layouts and Pavement Structures The station limits, layer thicknesses, and material types for each of the SPS-1 and SPS-2 test sections were extracted from the SPS_PROJECT_STATIONS and TST_L05B tables in the LTPP database. The thicknesses in the TST_L05B table represent the LTPP regional support centersâ best estimates of the as-built layer thicknesses and materials. Layout diagrams were developed to display the stationing of the test sections at each site, identify the sections to be drained, show the locations of edgedrain outlets where video inspection had been done, and indicate the material types and thicknesses of the pavement layers. For the SPS-2 sites, the layout diagrams also indicate which sections were built with widened slabs and show the design concrete strength. The SPS-1 and SPS-2 layout diagrams are included in Appendix A. For the purposes of analyzing deflections measured at the SPS-1 and SPS-2 sites, the layer materials used in the differ- ent test sections were categorized in the following groups: Group Description AC Asphalt concrete (the combined thickness of all lifts) PCC Portland cement concrete AGG1 Unbound aggregate layer directly beneath AC or PCC layer LCB Lean concrete base ATB Dense-graded asphalt-treated base PATB Permeable asphalt-treated base HMAC Hot-mix asphalt concrete base AGG2 Unbound aggregate layer beneath a treated base layer CAM Cement-aggregate mixture These groups were then used in the layout diagrams to indicate the composition of the pavement layers. In most cases in the SPS-1 experiment, the AC layer is the combined thickness of lifts of dense-graded asphalt concrete (material code 1 in the LTPP database). In some cases, (Arizona 040160, all of the Delaware SPS-1 sections, and all of the New Mexico SPS-1 sections), the top layer is an open- graded asphalt friction course (material code 2). In all cases in the SPS-2 experiment, the PCC layer is jointed plain concrete pavement (JPCP, material code 4). The Arizona SPS-1 site has one supplemental section (040160) with a JPCP surface layer, and another supplemental section (040163) with a roller-compacted concrete layer (material code 20, âotherâ) and an open-graded asphalt friction course. Materials categorized in this study as AGG1 are unbound granular materials directly beneath the AC or PCC layer; they are typically identified in the LTPP database as crushed stone (303) or crushed gravel (304). The materials categorized as AGG2 are unbound granular materials or gravel-soil mix- tures beneath a treated base layer. For this analysis, the mate- rial types listed in the LTPP database that were placed in the AGG2 group include âsoil-aggregate mixture, predominantly fine-grainedâ (307), âsoil-aggregate mixture, predominantly coarse-grainedâ (308), and a number of soils with a gravel or sand component. For backcalculation purposes, some 16 y = -0.2474x2 + 1.5617x R2 = 0.9876 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 One-year, one-hour rainfall (in/hr) Tw o- ye ar , o ne -h ou r r ai nf al l (i n/h r) Figure 8. One-year, 1-hour precipitation versus 2-year, 1-hour precipitation for SPS-1 and SPS-2 sites.
judgment was applied in distinguishing between a granular material considered as a layer in the pavement structure versus a granular material considered as part of the founda- tion and/or a filter layer intended to block fines from infil- trating a permeable base. Although the LTPP database may identify eight or nine different layer materials (including multiple AC lifts and mul- tiple granular subbase and select fill materials) above the subgrade for a given section, for the purposes of this study the SPS-1 test sections were analyzed as either one, two, or three layers above the subgrade. The SPS-1 sections fall into one of the following five groups: ⢠AC Group AâAC alone or AC over aggregate (AGG1), ⢠AC Group BâAC over asphalt-treated base (ATB), ⢠AC Group CâAC over asphalt-treated base (ATB) over aggregate (AGG2), ⢠AC Group DâAC over permeable asphalt-treated base (PATB) over aggregate (AGG2), and ⢠AC Group EâAC over asphalt-treated base (ATB) over permeable asphalt-treated base (PATB) The SPS-2 sections were analyzed as two layers above the subgrade, and all but a few fell into one of the following three groups: ⢠PCC Group AâPCC over dense-graded aggregate, ⢠PCC Group BâPCC over lean concrete base, and ⢠PCC Group CâPCC over permeable asphalt-treated base. The SPS-2 sections that did not fall into one of the three PCC groups included the following: ⢠Supplemental sections where the base layer is identified in the database as hot-mix asphalt concrete (material code 319): Arizona 040266, 040267, and 040268; Nevada 320259; and Washington 530259. ⢠Supplemental sections where the base layer is identified as an asphalt-treated mixture (material code 321): North Carolina 370259 and 370260. ⢠Supplemental sections where the base layer is identified as a cement-aggregate mixture (material code 331): Kansas 200259, Ohio 390261 and 390262, and Wisconsin 550261. ⢠A supplemental section where the concrete slab was con- structed on the subgrade: Colorado 080259. The layer thicknesses shown in the layout diagrams were obtained from the TST_L05B table in Release 19 of the LTPP database. It should be noted that there are quite a few minor differences (sometimes one or two tenths of an inch, but in a few cases up to a half of an inch) between the layer thicknesses reported in Release 19 and those reported in earlier releases. Soils at the SPS-1, SPS-2, and MnRoad Sites Information on the natural drainage characteristics of the soils was obtained, in most cases, from county soil reports published by the U.S. Department of Agricultureâs Natural Resources Conservation Service (NRCS). For a few of the SPS-1 and SPS-2 sites for which a printed copy of the county soil report could not be obtained, information on the soils at the sitesâ locations was requested from a state or local NRCS office or the countyâs agricultural extension office. For several of the SPS-1 and SPS-2 sites, the most recent county soil report had been published prior to the construc- tion not only of those test sections, but also of any roadway along that alignment. This made it difficult to identify the predominant soil type at the test sections. Latitudinal and longitudinal data, as well as geographical features such as rivers and streams, are in those cases especially useful in attempting to pinpoint the location of an SPS-1 or SPS-2 site on the map sheets in the county soil reports. The drainage class (also called the natural drainage class) of a soil describes the frequency and duration of periods of saturation or partial saturation in the absence of artificial (fabricated) drains or irrigation. Drainage classes are, how- ever, primarily defined for agricultural purposes, which explains why, for example, very rapid water movement through the soil is classified as âexcessive,â when from a pave- ment engineering perspective the more rapidly water moves through the soil, the better. There are seven drainage classes defined in the Soil Survey Manual: Excessively drainedâWater is removed very rapidly. The occurrence of internal free water commonly is very rare or very deep. The soils are commonly coarse-textured and have very high hydraulic conductivity or are very shallow. Somewhat excessively drainedâWater is removed from the soil rapidly. Internal free water occurrence commonly is very rare or very deep. The soils are commonly coarse-textured and have high saturated hydraulic conductivity or are very shallow. Well drainedâWater is removed from the soil readily but not rapidly. Internal free water occurrence commonly is deep or very deep; annual duration is not specified. Water is avail- able to plants throughout most of the growing season in humid regions. Wetness does not inhibit growth of roots for signifi- cant periods during most growing seasons. The soils are mainly free of the deep to redoximorphic features that are related to wetness. Moderately well drainedâWater is removed from the soil somewhat slowly during some periods of the year. Internal free water occurrence commonly is moderately deep and transitory through permanent. The soils are wet for only a short time within the rooting depth during the growing season, but long enough that most mesophytic crops are affected. They com- monly have a moderately low or lower saturated hydraulic conductivity in a layer within the upper 1 m, periodically receive high rainfall, or both. 17
Somewhat poorly drainedâWater is removed slowly so that the soil is wet at a shallow depth for significant periods during the growing season. The occurrence of internal free water commonly is shallow to moderately deep and transitory to permanent. Wetness markedly restricts the growth of mesophytic crops, unless artificial drainage is provided. The soils commonly have one or more of the following characteristics: low or very low sat- urated hydraulic conductivity, a high water table, additional water from seepage, or nearly continuous rainfall. Poorly drainedâWater is removed so slowly that the soil is wet at shallow depths periodically during the growing season or remains wet for long periods. The occurrence of internal free water is shallow or very shallow and common or persistent. Free water is commonly at or near the surface long enough during the growing season so that most mesophytic crops cannot be grown, unless the soil is artificially drained. The soil, however, is not continuously wet directly below plow-depth. Free water at shal- low depth is usually present. This water table is commonly the result of low or very low saturated hydraulic conductivity of nearly continuous rainfall, or of a combination of these. Very poorly drainedâWater is removed from the soil so slowly that free water remains at or very near the ground surface during much of the growing season. The occurrence of internal free water is very shallow and persistent or permanent. Unless the soil is artificially drained, most mesophytic crops cannot be grown. The soils are commonly level or depressed and frequently ponded. If rainfall is high or nearly continuous, slope gradients may be greater. (25) A second means of classifying soil drainage characteristics is by hydrologic soil group, which indicates the estimated runoff from precipitation. Soils not protected by vegetation are assigned to one of four groups, according to the intake of water when the soils are thoroughly wet and receive precipi- tation from long-duration storms. Group AâSoils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group BâSoils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group CâSoils having a slow infiltration rate when thor- oughly wet. These consist chiefly of soils having a layer that impedes downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group DâSoils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a per- manently high water table, soils that have a claypan at or near the surface, and soils that are shallow over nearly impervious mate- rial. These soils have a very slow rate of water transmission. (25) Three dual hydrologic groupsâA/D, B/D, and C/Dâare also recognized for those wet soils that can be adequately drained. The first letter applies to the drained condition, the second to the undrained. Only soils that are rated D in their natural condition can be assigned to a dual group, and then only if drainage is feasible and practical. Brief descriptions of the drainage characteristics of the pre- dominant type or types of soil at most of the SPS-1 and SPS-2 site locations are given below. The sites are listed alphabeti- cally by state. The descriptions are based on information obtained from county soil reports and from soil series avail- able on the Internet, as well as other sources (26-29). It is apparent that at some of the SPS-1 and SPS-2 sites, water that enters pavement structures is likely to be able to drain down- ward through the natural subgrade, while at other sites, where it is not likely to drain downward, a subdrainage system would be needed to allow the water to drain laterally. Alabama SPS-1: Appling sandy loam, with slopes ranging from 1% to 6%. This soil is an SM or SM-SC in the Unified Soil Classification System (ASTM D-2498) and an A-2 in the AASHTO Soil Classification System (AASHTO M-145). It is in hydrologic Group B. The Appling series consists of very deep, well drained, moderately permeable soils, on ridges and side slopes of the Piedmont uplands. They are deep to sapro- lite and very deep to bedrock. They formed in residuum weathered from felsic igneous and metamorphic rocks. Appling sandy loam is a soil low in natural fertility and organic content. Its natural vegetation is forest, and where it has been cleared it is used for pasture and crops. Photos of the Alabama SPS-1 site and of some soil that has accumulated at an outlet in one of the drained test sections are shown in Figures 9, 10, and 11. The taxonomic classification of Appling soils is as fine, kaolinitic, thermic Typic Kanhapludults. Fine refers to the soil texture, kaolinitic refers to the mineralogical composition being predominantly clay, and thermic indicates that the 18 Figure 9. Alabama SPS-1 site.
mean annual soil temperature is between 15°C and 22°C and that the mean winter and mean summer soil temperatures differ by less than 5°C. These soils are typical of the udult (humid) suborder of ultisols found throughout much of the southeastern United States (see Figures 12 and 13). Arizona SPS-1: Milkweed-Quartermaster-Buckndoe complex, with slopes ranging from 2% to 20%. This is a mix of about 50% Milkweed series soils, 30% Quartermaster series soils, 15% Buckndoe series soils, and 5% other soils. Milkweed, Quartermaster, and Buckndoe soils are classified as GP, GM-GC, GP-GM, or GM in the unified system and as A-1 or A-2 in the AASHTO system. Milkweed and Quarter- master soils are classified in hydrologic Group C; Buckndoe soils are in Group B. A photo of the Arizona SPS-1 site is shown in Figure 14. All three series in this complex are well drained soils, formed on fan terraces of plateaus at elevations of 4,600 to 5,500 ft. The Milkweed, Quartermaster, and Buckndoe series are shallow, moderately deep, and deep, respectively, to hard- pan. Milkweed and Buckndoe soils are derived predomi- nantly from sedimentary and igneous rocks; Quartermaster soils are derived predominantly from limestone and basalt. These soils make for grazeable woodland, firewood produc- tion, and wildlife habitat. The taxonomic classifications of the three soils are similar. All are inceptisols, which are âyoung,â that is, only mildly weathered. The distribution of the major suborders of incep- tisols in the United States is shown in Figure 15. Milkweed soils are classified as loamy-skeletal, mixed, superactive, mesic, shallow Petrocalcic Calciustepts. Loamy-skeletal refers to the soil texture, mixed refers to the mineralogical compo- sition, and superactive refers to the cation exchange capacity of the clay component. Mesic indicates that the mean annual soil temperature is between 8°C and 15°C and that the mean winter and mean summer soil temperatures differ by more than 5°C. Petrocalcic Calciustepts are soils with a cemented calcium carbonate horizon. Quartermaster soils are classified as fine- loamy, mixed, superactive, mesic Aridic (dry) Calciustepts. Buckndoe soils are classified as loamy-skeletal, mixed, super- active, mesic Aridic Calciustepts. Note that Calciustepts, being a fairly minor suborder of inceptisols, are not shown in Figure 15. They are found mainly on the Great Plains of the United States, as well as in the intermountain valleys of the western states. Arizona SPS-2: Perryville-Rillito complex, with slopes ranging from 0% to 3%, and Gunsight-Pinal complex, with 1% to 10% slopes. These are very deep, well drained to some- what excessively drained soils, formed on alluvial fans and terraces. Perryville, Rillito, and Gunsight soils are in hydro- logic Group B; Pinal soils are in hydrologic Group D. A photo of the Arizona SPS-2 site is shown in Figure 16. The taxonomic classifications of these soils identify them as hyperthermic (mean annual soil temperature greater than 22°C and mean winter and mean summer soil temperatures different by more than 5°C). The predominant Perryville, Rillito, and Gunsight soils are Haplocalcids, meaning that they are typical of calcid (carbonate) aridisols, the desert soils found in much of the southwestern United States, as shown in Figure 17. Arkansas SPS-1: Dundee fine sandy loam. This soil is an ML or CL-ML in the Unified Soil Classification System and an A-4 in the AASHTO system. It is in hydrologic Group C. The Dundee series consists of very deep, somewhat poorly drained soils that formed in loamy alluvium. These soils are level to gently sloping soils on natural levees and low terraces along former channels of the Mississippi River and its tributaries in 19 Figure 10. Water and soil at drainage outlet at Alabama SPS-1 site. Figure 11. Soil accumulation in drainage outlet at Alabama SPS-1 site.
Figure 12. Dominant soil orders of the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service.
21 Figure 13. Distribution of ultisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service. Figure 14. Arizona SPS-1 site. Figure 15. Distribution of inceptisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service. Figure 16. Arizona SPS-2 site. Figure 17. Distribution of aridisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service.
the southern Mississippi Valley. Dundee fine sandy loams have slopes of less than 1% and a shallow water table in the winter and spring. The typical crop grown in this soil is cotton. A photo from the Arkansas SPS-1 site is shown in Figure 18. The taxonomic classification of Dundee soils are as fine-silty, mixed, active, thermic Typic Endoaqualfs. The endo- prefix indicates that these soils tend to be saturated. These soils belong to the aqualf (wet) suborder of alfisolsâthe fertile but poorly draining soils that are commonly found in a broad swath from the Great Lakes region, down through the Mississippi Valley all the way to the Gulf of Mexico, as shown in Figure 19. Arkansas SPS-2: Savannah-Urban land complex, with 3% to 8% slopes. This soil is an SM or ML in the unified system and an A-2 or A-4 in the AASHTO system. It is in hydrologic Group C. The Savannah series consists of moderately well drained, moderately slowly permeable soils with a fragipan (a dense, brittle layer). A water table is perched above the fragipan at a depth of 1.5 to 3.0 ft below the surface during wet seasons (January to March). Savannah soils are formed in loamy marine or fluvial terrace deposits. They are on uplands and terraces that range from nearly level to moderately steep. The natural vegetation of Savannah soils is mixed hardwoods and pines; as the photos in Figures 20 and 21 show, the vicin- ity of the Arkansas SPS-2 site is forested. Perhaps the most striking thing about the Arkansas SPS-2 site, from the standpoint of drainage as an experimental pave- ment design factor, is how steep and variable the longitudinal slopes are. This is evident in the photos in Figures 20 and 21. The taxonomic classification of Savannah soils is as fine- loamy, siliceous (sandy), semiactive, thermic Typic Frag- iudults. The fragi- prefix refers to the presence of a fragipan. Like the soil at the Alabama SPS-1 site, the soil at the Arkansas SPS-2 sites belongs to the udult (humid) suborder of ultisols, found throughout much of the southeastern United States (see Figure 13). Colorado SPS-2: Vona loamy sand, 1% to 3% slopes. This soil is an SM in the unified system and an A-2 or A-4 in the 22 Figure 18. Arkansas SPS-1 site. Figure 19. Distribution of alfisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service. Figure 20. Arkansas SPS-2 site. Figure 21. Arkansas SPS-2 site.
AASHTO system. The Vona series consists of very deep, well to somewhat excessively drained, moderately rapid and rap- idly permeable soils that formed in eolian or partly wind- reworked alluvial materials. Vona soils are found on hills, ridges, plains, and uplands and are frequently parallel to major river channels. These soils are used for grazing cattle and for irrigated and drought-tolerant crops. The taxonomic classification of Vona soils is as coarse- loamy, mixed, superactive, mesic Aridic Haplustalfs. Mixed refers to their mineralogical content, superactive refers to the cation exchange capacity of the clay component, and mesic indicates that the mean annual soil temperature is between 8°C and 15°C and that the mean winter and mean summer soil temperatures differ by more than 5°C. Aridic Haplustalfs are among the drier soils of the ustalf (dry) suborder of alfisols (see Figure 19). Delaware SPS-1: Pocomoke sandy loam. This soil is an SM in the unified system and an A-2 or A-4 in the AASHTO sys- tem. The Pocomoke series consists of very deep, very poorly drained soils, formed in sandy sediments, mostly of marine origin, on low-lying terraces of the Atlantic and Gulf Coastal Plains. Slopes range from 0% to 2%. The water table is sea- sonally at or near the surface, and it remains at this level for long periods of time unless the soil is artificially drained. The flatness of the Delaware SPS-1 site is evident in Figure 22. The taxonomic classification of Pocomoke soils is as coarse-loamy, siliceous, active, thermic Typic Umbraquults. The umbra- prefix indicates that the A horizon (the top 10 in. or so) is dark in color, due to the organic matter present. Aquults are aquic (wet) ultisols (see Figure 13). Delaware SPS-2: Sassafras sandy loam, with 0% to 2% slopes. The Delaware SPS-2 site is located very near the Delaware SPS-1 site, but its soil is of a different type, with bet- ter drainage characteristics. The textures of the two soils are similar: like Pocomoke sandy loam, Sassafras sandy loam is an SM or ML in the unified system and an A-2 or A-4 in the AASHTO system. One key difference is that the depth to the seasonal high water table is greater than 5 ft for the Sassafras soil at the SPS-2 site, but 0 ft for the Pocomoke soil at the SPS-1 site. So while the SPS-1 siteâs soil is classified as very poorly drained, the SPS-2 siteâs soil is classified as well drained. A photo of the Delaware SPS-2 site is shown in Figure 23. The taxonomic classification of Sassafras soils is as fine- loamy, siliceous, semiactive, mesic Typic Hapludults. This is similar to the classification of the Pocomoke soils at the SPS-1 site. One curious difference is that the SPS-1 siteâs soil is clas- sified as belonging to the thermic temperature regime (mean annual temperature of 15°C to 22°C), while the SPS-2 siteâs soil is classified as belonging to the mesic regime (mean annual temperature of 8°C to 15°C). In fact, as shown in Tables 12 and 13, the two sites have nearly the same mean annual tem- perature (about 13°C), as one would expect, considering how close they are to each other. So while one soil series might more typically be found in the thermic regime and the other in the mesic regime, in this particular instance, these two locations both meet the definition of the thermic regime. Florida SPS-1: Pahokee muck. This is classified as a Pt in the Unified Soil Classification System; there is no correspon- ding class in the AASHTO system. It is in the A/D dual hydrologic class. Pahokee soils, which occupy the central and southern parts of the Everglades, are nearly level, very poorly drained organic soils that are 36 to 51 in. thick over lime- stone. Typically, they have a surface layer of black muck, over a black and dark reddish brown muck, resting on hard lime- stone. Pahokee mucks are formed in organic deposits of freshwater marshes. In natural areas the water table is at or above the surface for much of the year; in other areas the water table is controlled by artificial means. 23 Figure 22. Delaware SPS-1 site. Figure 23. Delaware SPS-2 site.
The taxonomic classification of Pahokee soils is as euic, hyperthermic Lithic Haplosaprists. Euic indicates a high base content. The hyperthermic soil moisture regime has a mean annual soil temperature greater than 22°C and a difference of more than 5°C between the mean summer and mean winter soil temperatures. Lithic means that the soils are near stone. They belong to the saprist (unrecognizable fibers) suborder of histosols, organic soils found in wetlands (see Figure 24). Iowa SPS-1: Fayette silt loam, 2% to 5% slopes. This soil is a CL or CL-ML soil in the Unified Soil Classification System and an A-4 or A-6 in the AASHTO system. It is in hydrologic Group B. The Fayette series consists of very deep, well drained, moderately permeable soils, formed in loess. These soils are on convex crests, interfluves and side slopes on uplands, and on treads and risers on high stream terraces. The seasonal high water table is more than 6 ft deep. The taxo- nomic classification of Fayette silt loam is fine-silty, mixed, superactive, mesic Typic Hapludalfs, of the alfisol order (see Figure 19). The Iowa SPS-1 site is shown in Figure 25. Kansas SPS-1: Naron fine sandy loam, 1% to 3% slopes. This soil is an SM, SM-SC, ML, or CL-ML in the Unified Soil Classification System and A-2 or A-4 in the AASHTO system. It is in hydrologic Group B. The seasonal high water table is more than 6 ft deep. The Naron series consists of very deep, well drained, moderately permeable soils that formed in loamy eolian sediments. These soils are on dunes on terraces in river valleys of the Great Bend Sand Plains. The taxonomic classification of Naron soils is as fine- loamy, mixed, superactive, mesic Udic Argiustolls. The argi- prefix refers to the presence of a clay horizon. These soils belong to the ustic (intermittently dry during the summer) suborder of mollisolsâthe dark, soft, grassland soils that cover much of the Great Plains, as well as much of Iowa and northern and central Illinois (Figure 26). The Kansas SPS-1 site is shown in Figure 27. Kansas SPS-2: Hobbs silt loam, channeled, and Clime- Sogn complex, with 5% to 20% slopes. The Kansas SPS-2 site is shown in Figure 28. Hobbs silt loam is a CL or CL-ML in the Unified Soil Classification System and an A-4 or A-6 in the AASHTO sys- tem. It is in hydrologic Group B. The seasonal water table is more than 6 ft deep. The Hobbs series consists of very deep, well drained, moderately permeable soils that formed in strat- ified, silty alluvium. These soils are on flood plains, foot slopes, and alluvial fans. The Hobbs silt loam soil is deep, nearly level soil with entrenched stream channels along intermittent drainageways. This soil is mostly used for range- land and wildlife areas. 24 Figure 24. Distribution of histosols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service. Figure 25. Iowa SPS-1 site. Figure 26. Distribution of mollisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service.
The taxonomic classification of Hobbs soils is as fine-silty, mixed, superactive, nonacid, mesic Mollic Ustifluvents. Mol- lic refers to a soft, dark, highly organic surface layer. The usti- prefix refers to intermittent dryness in summer. These soils belong to the fluvent (formed from alluvial deposits) subor- der of entisolsâa category that encompasses a wide range of ânewâ soils with little in common other than the near or total lack of soil profile development (Figure 29). The Clime-Sogn complex consists of well drained and somewhat excessively drained soils, some moderately deep (Clime) and some shallow (Sogn), on uplands. The complex is 50% to 80% Clime soils and 10% to 30% Sogn soils. These soils are best suited for rangeland; they have poor potential for cropland. The Clime series consists of moderately deep, well drained, slowly permeable soils on uplands, formed in residuum from calcareous clayey shale. Clime is in the CL or CH class in the Unified Soil Classification System and an A-7 or A-6 in the AASHTO system. It is in hydrologic Group C. The taxonomic classification of the Clime series is as fine, mixed, active, mesic Udorthentic Haplustolls. Udorthentic refers to the character- istics of the surface layer (that is, resembling udic entisols such as relatively steep slopes of exposed loess or shale). Clime soils belong to the ustic (dry in summer) suborder of mollisols (see Figure 26). The Sogn series consists of shallow and very shallow, some- what excessively drained, soils that formed in uplands from residuum weathered from limestone. Sogn is in the CL class in the unified system and in the A-7 or A-6 class in the AASHTO system. It is in hydrologic Group D. The taxo- nomic classification of Sogn is as loamy, mixed, superactive, mesic Lithic Haplustolls. Lithic means near stone. Like the Clime soils that share this complex, Sogn soils are in the ustic suborder of mollisols (see Figure 26). Louisiana SPS-1: Brimstone silt loam. This soil is a CL-ML or CL in the Unified Soil Classification System and an A-4 or A-6 in the AASHTO system. It is in hydrologic Group D. The Brimstone series consists of deep, poorly drained, slowly permeable soils that are high in exchangeable sodium. They formed in loamy sediments on low Late Pleistocene terraces. These soils are on broad flats at intermediate elevations. Slopes range from 0% to 1%. Water runs off the surface slowly and stands in low places for short periods after a heavy rain. The surface layer remains wet for long periods after a heavy rain. The seasonal high water table fluctuates between the surface and a depth of 1.5 ft from December through April. This type of soil is well suited for cultivating crops such as rice and soybeans and moderately well suited for pasture, although both cultivated crops and pasture plants require drainage to survive in this soil. The Louisiana SPS-1 site is shown in Figure 30. 25 Figure 27. Kansas SPS-1 site. Figure 28. Kansas SPS-2 site. Figure 29. Distribution of entisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service.
The taxonomic classification of Brimstone soils is as fine- silty, siliceous, superactive, thermic Glossic Natraqualfs. Glossic refers to the tongued interlayering of the horizons. The natr- prefix refers to the presence of a natric horizon (a layer of silicate clay with more than 15% exchangeable sodium ions). These soils belong to the aquic (wet) suborder of alfisols (see Figure 19). Michigan SPS-1: Capac loam, with 0% to 4% slopes. This soil is an ML or CL in the Unified Soil Classification System and an A-4 in the AASHTO system. The Capac series consists of very deep, somewhat poorly drained, moderately slowly permeable soils that formed in loam or clay loam calcareous till. These soils are on moraines and till plains of the Wiscon- sinian glaciation and typically have slopes ranging from 0% to 6%. The taxonomic class of Capac soils is fine-loamy, mixed, active, mesic Aquic Glossudalfs. The gloss- prefix in the name means that the soil horizons are tongued, or interlacing. Glossudalfs are in the udalf (moist) suborder of alfisols (see Figure 19). The Michigan SPS-1 site is shown in Figure 31. Michigan SPS-2: Pewamo clay loam. This soil is a CL in the Unified Soil Classification System and an A-6 or A-7 in the AASHTO system. It is in the C/D dual hydrologic class. The water table is near or above the surface in winter and spring. The Pewamo series consists of very deep, very poorly drained soils formed in till on moraines and lake plains. Permeability is moderately slow. This soil is found in low areas and depres- sions and is subject to frequent ponding. Figure 32 is a photo from the Michigan SPS-2 site, showing a pond alongside the roadway. The surface of the water in the pond appeared to be at a level not very different from the surface of the pavement. The taxonomic classification of Pewamo soils is as fine, mixed, active, mesic Typic Argiaquolls. The argi- prefix refers to the presence of a clay horizon. They are in the aquic (wet) suborder of mollisols (see Figure 26). Montana SPS-1: Virgelle-Absher complex, with slopes ranging from 0% to 3%. This soil is about 55% Virgelle loamy fine sand and 30% Absher clay loam. The Virgelle sand occu- pies the smooth slopes and convex areas, and the Absher soil occupies shallow depressions. A photo of the Montana SPS-1 site is shown in Figure 33. The Virgelle series consists of very deep, well drained soils that formed mainly in alluvium or eolian. These soils are on stream terraces and till plains at elevations of 3,300 to 3,600 ft. These soils are suitable for crops such as wheat and for rangeland or pastureland. This soil is an SM in the unified system and an A-2 in the AASHTO system. It is in hydrologic Group C. The seasonal high water table is more than 6 ft below the surface. The taxonomic classification of Virgelle soils is as clayey, mixed over smectitic, frigid Entic Haplustolls. Smectite is the name used for clays that used to be called montmorillonite. 26 Figure 30. Louisiana SPS-1 site. Figure 31. Michigan SPS-1 site. Figure 32. Michigan SPS-2 site.
natric horizon. These soils belong to the ustalf (dry) suborder of alfisols (see Figure 19). MnRoad: Hayden loam, with slopes ranging from 2% to 6%, and Dundas and Ames silt loams with 0% to 3% slopes. The MnRoad site is shown in Figure 34, and a diagram from the county soil report, showing the drainage characteristics of the major soil series of Wright County, Minnesota, is shown in Figure 35. Some of the MnRoad test sections are located in areas of fairly flat or mild slopes, with the pave- ment surface higher than the surrounding ground, while other test sections are located in low areas between hills, with the surrounding ground higher than the pavement sur- face or with ponded water alongside the roadway at almost the level of the pavement surface. In general, this variability in terrain makes the MnRoad site seem less suited for the study of subsurface drainage than for the study of other pavement design factors. 27 Figure 33. Montana SPS-1 site. Figure 34. MnRoad site. Figure 35. Major soils series in Wright County, Minnesota. Frigid refers to the soil moisture regime (mean annual soil temperature between 0°C and 8°C, and greater than 5°C difference between the mean winter and mean summer soil temperature). These soils belong to the ustic (intermittently dry) suborder of mollisols (see Figure 26). The Absher series consists of very deep, well, and moder- ately well drained soils that formed in till, glaciofluvial deposits, and alluvium derived from many sources of geologic materials. These soils are on alluvial fans, stream terraces, drainageways, sedimentary plains, and till plains. This soil is a CL in the unified system and an A-6 or A-7 in the AASHTO system. It is in hydrologic Group D. The seasonal high water table is more than 6 ft below the surface. The taxonomic classification of the Absher series is as fine, smectitic, frigid, leptic Torrertic Natrustalfs. Torrertic refers to a surface horizon with vertical cracks indicative of shrink- swell behavior. The natr- prefix refers to the presence of a
Hayden loam is an ML-CL in the unified system and an A-6 in the AASHTO system. The Hayden series consists of deep, well drained, moderately permeable soils that formed in cal- careous loamy glacial till on glacial moraines and till plains. In general, the slopes are gently undulating but irregular, and small areas of poorly drained soils are found in depressions between the slopes. The taxonomic classification of Hayden soils is as fine-loamy, mixed, superactive, mesic Glossic Hapludalfs. They belong to the udalf (moist) suborder of alfisols (see Figure 19). The Dundas and Ames silt loam map unit is more than 60% Dundas soils. Dundas silt loam is an MH or OH in the unified system and an A-5 in the AASHTO system. The Dundas series consists of very deep, nearly level, poorly drained soils that formed in loamy calcareous till on moraines. They formed mostly in friable calcareous, glacial till of the late Wisconsin stage. These soils have moderately low saturated hydraulic conductivity. Dundas and Ames are fair to good for crops and good for pasture; wetness is, how- ever, a problem because water moves slowly through these soils even with artificial drainage. The taxonomic classification of Dundas soils is as fine-loamy, mixed, superactive, mesic Mollic Endoaqualfs. Mollic refers to a mollic (soft, dark, organic) surface layer. The endo- prefix in- dicates that these soils tend to be saturated. These soils belong to the aqualf (wet) suborder of alfisols (see Figure 19). Nebraska SPS-1: Geary silty clay loam, with 3% to 7% slopes, eroded; and Hastings silty clay loam, 3% to 7% slopes, eroded. The Geary silty clay loam is on ridge crests and gently side slopes. It is a CL in the unified system and an A-6 in the AASHTO system. The Hastings soils, which occur at higher elevations than the Geary soils, are CL or CH in the unified system and an A-6 or A-7 in the AASHTO system. The main concerns about Geary and Hastings soils, with respect to their suitability for a highway location, are their high to very high susceptibility to frost action and their erodibility. The Geary series consists of very deep, well drained, mod- erately or moderately slowly permeable soils that formed in loess. These soils are on uplands. The taxonomic classifica- tion of Geary soils is as fine-silty, mixed, superactive, mesic Udic Argiustolls. The argi- prefix refers to the presence of a clay horizon. These soils belong to the ustoll (intermittently dry) suborder of mollisols (see Figure 26). The Hastings series consists of very deep, well drained soils on uplands. They formed in silty loess. Permeability is mod- erately slow. The taxonomic classification of Hastings soils is as fine, smectitic, mesic Udic Argiustolls. Like the Geary soils, they belong to the ustoll (intermittently dry) suborder of mollisols (see Figure 26). North Carolina SPS-2: Cecil sandy loam, with slopes rang- ing from 2% to 8%. Soils in the Cecil series are very deep, well drained, moderately permeable soils on ridges and side slopes of the Piedmont uplands. They are deep to saprolite and very deep to bedrock. They formed in residuum weathered from felsic, igneous, and high-grade metamorphic rocks. They are well drained, with medium to rapid runoff, medium internal drainage, moderate permeability, and low shrink-swell potential. The seasonal high water table is below 6 ft. Cecil soils are found throughout the Piedmont area of Alabama, Georgia, North Carolina, South Carolina, and Virginia. The taxonomic classification of Cecil soils is as fine, kaolinitic, thermic Typic Kanhapludults. (Note that this is the same taxonomic classification as at the Alabama SPS-1 site.) Kaolinitic indicates that the subsoil is clayey. Thermic indi- cates that the mean annual soil temperature is between 15°C and 22°C and that the mean winter and mean summer soil temperatures differ by less than 5°C. These soils are typical of the udult (humid) suborder of ultisols, found throughout much of the southeastern United States (see Figure 13). North Dakota SPS-2: Fargo silty clay. This soil is a CH in the unified system and an A-7-6 in the AASHTO system. It is in hydrologic Group D. The seasonal high water table is 0 to 3 ft below the surface. The Fargo series consists of very deep, poorly drained and very poorly drained, slowly permeable soils that formed in calcareous, clayey lacustrine sediments. These soils are on glacial lake plains, floodplains, and gently sloping side slopes of streams within glacial lake plains. Slopes range from 0% to 6%. A system of legal drains, section lines, road ditches, and field drains remove surface water from most Fargo soils. The taxonomic classification of Fargo soils is as fine, smec- titic, frigid Typic Epiaquerts. The epi- prefix indicates the presence of a perched water table. These soils are in the aquert (wet) suborder of vertisols, which consist of shrinking and swelling clay soils. As shown in Figure 36, vertisols are found in fairly few places in the United States. The greatest concen- trations of dry vertisols are in eastern Texas and western South Dakota. The greatest concentrations of wet vertisols are along the lower Mississippi River and along the border of North Dakota with Minnesota, where, unfortunately, the North Dakota SPS-2 site is located. Oklahoma SPS-1: Foard-Hinkle complex, with 1% to 3% slopes. This is a mix of Foard silt loam and Hinkle silt loam. The Oklahoma SPS-1 site is shown in Figure 37. Both the Foard and the Hinkle series consist of very deep, well drained, very slowly permeable soils that formed in ma- terial weathered from old alluvium of granitic outwash. Both are nearly level to gently sloping soils on broad summits and shoulder slopes of terrace pediments in the Central Rolling Red Plains and the Wichita Mountains. The taxonomic clas- sification of both Foard and Hinkle soils is fine, smectitic, thermic Vertic Natrustolls. Vertic indicates the presence of a surface layer with shrink-swell potential. The natr- prefix refers to the presence of natric horizon. These soils are of the ustoll (dry) suborder of mollisols (see Figure 26.) Texas SPS-1: Nueces-Sarita complex, with 0% to 3% slopes. A photo of the Texas SPS-1 site is shown in Figure 38. Both Nueces and Sarita soils are very deep, well drained, moderately 28
rapidly permeable soils, formed in sandy eolian materials over- lying loamy sediments. These soils are on gently undulating sandy eolian plains associated with vegetated dunes on the Sandsheet Prairie of the South Texas Coastal Plain. The taxonomic classification of Nueces soils is as loamy, mixed, superactive, hyperthermic Arenic Paleustalfs. Arenic refers to the presence of a sandy horizon. The pale- prefix refers to old development. The taxonomic classification of Sarita soils is as loamy, mixed, active, hyperthermic Grossarenic Paleustalfs. Both Nueces and Sarita soils are in the ustalf (dry) suborder of alfisols (see Figure 19). Virginia SPS-1: Appling sandy loam, with 7% to 15% slopes. Other than the steeper slopes, this is the same soil as at the Alabama SPS-1 site and it has the same taxonomic clas- sification (fine, kaolinitic, thermic Typic Kanhapludults) as the Cecil sandy loam at the North Carolina SPS-2 site. A photo of the Virginia SPS-1 site is shown in Figure 39. Washington SPS-2: Ritzville silt loam. The Ritzville series consists of very deep and deep to duripan, well drained, mod- erately permeable soils formed in loess. Ritzville soils are located on uplands, including plateaus, benches, and canyon side slopes. Elevations range from 800 to 3,000 ft, and slopes range from 0% to 70%. These soils formed in loess. They have a small amount (less than 20%) of volcanic ash in the surface layer. These soils are in a semiarid climate with cool, moist win- ters and warm, dry summers. A photo of the Washington SPS-2 site is shown in Figure 40. The taxonomic classification of Ritzville soils is coarse-silty, mixed, superactive, mesic Calcidic Haploxerolls. These soils belong to the xeroll (dry summers, moist winters) suborder of mollisols (see Figure 26). Wisconsin SPS-1: Kennan sandy loam, with 8% to 30% slopes, and Seelyeville muck. Kennan soils are gently sloping to steep and are well drained. They are formed in sandy loam or loamy sand glacial till, and they are found on the tops and 29 Figure 36. Distribution of vertisols in the United States. SOURCE: U.S. Department of Agriculture, Natural Resources Conservation Service. Figure 37. Oklahoma SPS-1 site. Figure 38. Texas SPS-1 site. Figure 39. Virginia SPS-1 site.
sides of knolls, hills, and ridges on terminal and recessional moraines. They are classified as SM, SM-SC, ML, or CL-ML in the unified system and as A-2, A-4, or A-1 in the AASHTO system. The taxonomic classification of Kennan soils is as coarse-loamy, mixed, superactive, frigid Haplic Glossudalfs. The gloss- prefix in the name means that the soil horizons are tongued, or interlacing. Glossudalfs are in the udalf (moist) suborder of alfisolsâthe fertile but poorly draining soils that are commonly found in the Great Lakes and Mississippi Valley regions (see Figure 19). The Seelyeville series consists of very deep, very poorly drained soils that formed in organic materials more than 51 in. thick. These soils are on glacial outwash plains, valley trains, flood plains, glacial lake plains and glacial moraines. Seelyeville soil is a PT in the Unified Soil Classification System and an A-8 in the AASHTO system. The taxonomic classification is euic, frigid Typic Haplosaprists. Euic signi- fies that the soil is organic and has a pH of 4.5 or more. Seelyeville soils belong to the saprist (unrecognizable fibers) suborder of histosolsâorganic soils found in wetlands (see Figure 24). Wisconsin SPS-2: Rosholt silt-loam, Scott Lake silt loam, and Oesterle loam, all with slopes ranging from 0% to 2%. The Rosholt series consists of very deep, well drained soils that are moderately deep to sandy outwash. These soils formed mostly in loamy alluvial deposits and are underlain by stratified sandy outwash. They are classified as SM, SM-SC, ML, or CL-ML in the unified system and as A-2, A-4, or A-1 in the AASHTO system. The taxonomic classification of Rosholt soil is as a coarse-loamy, mixed, superactive, frigid Haplic Glossudalf (which is the same taxonomic classification as the Kennan soil at the nearby Wisconsin SPS-1 site). Scott Lake soils are moderately well drained and are found on broad flats adjacent to lower depressions. They are classi- fied as ML, CL-ML, SM, or SM-SC in the unified system and as A-4 in the AASHTO system. Their taxonomic classification is coarse-loamy, mixed, superactive, frigid Oxyaquic Glossu- dalfs. The moisture regime of this soil is indicated by the suborder name oxyaquic, meaning oxygenated water. The Oesterle series consists of very deep, somewhat poorly drained soils that are moderately deep to underlying sandy outwash. They formed dominantly in loamy alluvium underlain by sandy outwash on outwash plains, valley trains, stream terraces, glacial lake plains, and outwash areas on moraines. They are classified as CL-ML, SM-SC, CL, or SC in the unified system and as A-4 in the AASHTO system. Their taxonomic classification is coarse-loamy, mixed, superactive, frigid Aquic Glossudalfs. Traffic at the SPS-1 and SPS-2 Sites The 18-kip equivalent single-axle load (ESAL) levels at the SPS-1 and SPS-2 sites were determined by extracting ESAL estimates from the TRF_MON_EST_ESAL table and axle load distributions from the TRF_MONITOR_AXLE_ DISTRIBUTION table in the LTPP database. Axle load distribution data were available for 12 of the 18 SPS-1 sites and 11 of the 14 SPS-2 sites. Data were not avail- able for the SPS-1 sites in Alabama, Louisiana, Montana, Oklahoma, Texas, and Wisconsin, nor were data available for the SPS-2 sites in California, North Dakota, and Wisconsin. ESALs were calculated for the years in which axle load dis- tribution data were available, using the number of axles reported in each load range in the distribution, and load equivalency factors calculated as a function of structural num- ber (in turn calculated from as-built layer thicknesses and typical structural coefficients for layer materials) or slab thick- ness. Average annual ESALs for the site were calculated using the annual ESAL estimates for the different test sections at the site. The average annual ESAL estimates for each site were then used to calculate accumulated ESAL estimates from the date the section was opened to traffic to each of several dates when distress and profile measurements were taken. The monitor- ing dates used were those on which measurements were obtained for most or all of the test sections at the site. Estimated accumulated ESALs are plotted for each of the SPS-1 sites with available traffic data in Figure 41 and for each of the SPS-2 sites in Figure 42. The different scales on the ver- tical axes of the two figures should be noted. In general, the SPS-2 sites have carried more truck traffic than have the SPS-1 sites; more than half of the SPS-2 sites have carried more truck traffic than the two most heavily trafficked SPS-1 sites. Because so many of the SPS-1 sites are located on lower volume roads (compared with the SPS-2 sites), extrapolating the findings from this study, or any study involving SPS-1 and SPS-2 data, to higher accumulated ESAL levels will be less reliable for the SPS-1 sites than for the SPS-2 sites. 30 Figure 40. Washington SPS-2 site.
31 0 1 2 3 4 5 6 7 8 Jan-92 Dec-92 Dec-93 Dec-94 Jan-96 Dec-96 Dec-97 Dec-98 Jan-00 Dec-00 Dec-01 Dec-02 Jan-04 Dec-04 Time in service (years) A cc um ul at ed fl ex ib le E SA Ls (m illi on s) Arkansas Nevada Delaware Florida Kansas Arizona Virginia Iowa New Mexico Michigan Ohio Nebraska Figure 41. Estimated accumulated ESALs for SPS-1 sites with traffic data available.
32 0 2 4 6 8 10 12 14 16 18 20 22 24 26 Jan-92 Dec-92 Dec-93 Dec-94 Dec-95 Dec-96 Dec-97 Dec-98 Dec-99 Dec-00 Dec-01 Dec-02 Dec-03 Dec-04 Dec-05 Year A cc um ul at ed ri gi d ES AL s (m illi on s) Michigan Arkansas North Carolina Arizona Kansas Nevada Ohio Washington Delaware Colorado Michigan Nevada Arkansas Kansas Figure 42. Estimated accumulated ESALs for SPS-2 sites with traffic data available.
