Highway Research Council

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1 K. Vswni N. Reserch Engineer Highwy Highwy Reserch Council Virgini Coopertive Orgniztion Sponsored Jointly by the Virgini (A 1973 October C 73-R21 VHR A DESIGN GUIDE FOR SUBDIVISION PAVEMENTS IN VIRGINIA by Deprtment of Highwys nd the University of Virgini) Chrlottesville, Virgini

3 K. Vswni N. Reserch Engineer Highwy nd Virgini's design experience. For flexible pvements, it is divided Results two prts: (1) the evlution of the soil support vlue of the subgrde, the thick- into equivlencies of the pving mterils, nd the trffic in terms of vehicles per ness nd (2) design considertions such s the determintion of the required thick- dy; meet the design thickness index. For portlnd cement concrete pvements, it to bsed on trffic only. is design method is to be used s n lterntive to prgrph 3 (pges 4-), This nd Pvement Design", of Revised Subdivision Stndrds s conveyed by "Bse dted October 3, 1968, from the Deputy Commissioner nd Chief Engi- memorndum to the Bord of Supervisors of All Counties in the Secondry System. neer for ll mterils nd construction cn be found in the current Specifictions Deprtment of Highwys' Rod nd Bridge Specifictions" or pproprite "Virgini Offices or the Virgini Deprtment of Highwys, Mterils Division, 21 District Brod Street, Richmond, Virgini design of flexible pvement is E. on pges 4 to. concrete pvement design is given on pges 15 covered 16. nd Averg e Cli.forni Bering Rti o (CBR) of the Project_t_ ll cses, " Virgini Test Method for Conducting C iforni Bering In Tests" (Designtion VTM-8) is to be used for evluting the CBR. For ech Rtio sufficient CBR tests should be run to determine the true verge CBR vlue project the vrious soils in the subgrde. of verge CBR vlue of the project is the verge of the CBR test vlues rejecting the very low nd very high vlues. fter A DESIGN GUIDE FOR SUBDIVISION PAVEMENTS IN VIRGINIA by INTRODUCTION design method for subdivision rods is bsed on AASHO Rod Test ness index of the pvement nd the selection of the mterils nd lyer thicknesses specifictions. Specific testing procedures cn be found in "Virgini's supplementl Methods Mnul" or its revisions. Copies of these two documents my be ob- Test tined from the Mterils Engineers locted in Virgini Deprtment of Highwys' THE EVALUATION OF VARIABLES

4 fctor of soil could be obtined if its soil clssifiction is known s resiliency in Appendix I, pge A-1. shown 1.5 Medium low 2.0 Medium Very low 3.0 predicted regionl resiliency fctors re given in Figure 1 (pge 3) Appendix H (pges A-2 to A-6), se fctors re vlid when the moisture nd of the subgrde soil is t or ner optimum. optimum moisture content is determined by AASHO Test Method Designtion T This test content usully not necessry unless visul observtions indicte it should be mde. is with moisture contents percent bove the optimum will need specil Soils.Resih,'ency F,ctor (R. F.) subgrde soils hve been divided into five clssifictions bsed on resiliency properties. resiliency fctors re given in Tble 1o their TABLE 1 RESILIENCY FACTORS FOR SOILS Degree of Resiliency R. F. High.0 Low 2.5 tretment or will be undercut. -2-

5 -3-

6 will be evluted in the sme mnner s given in prgrph 1 Trffic 2 "Me hod of Determining Trffic Usge of Revised Subdivision Stndrds" pge subdivision rods in Virgini usully consist of one, two, or three lyers different mterils of vrying depth over the subgrde. two- nd three-lyer of systems re shown in Figure 2. h 1 Thick. Equiv. 1 h 2 Thick. Equiv. 2,h Thick. Equiv. 3 3 \\\\\\\\\\\\\\\ or Bse 2 Thick. Equiv. 2 Subbse \\\ \\\\\\\\\ \ \\\\ \\.\\\ \\ Subgrde soil support vlue nd the trffic s discussed in the preceding prgrphs to the determintion of the strength required of the pvement. This strength re- led is termed the "thickness index" of the pvement. thickness index quirement is stisfied by providing mterils of known strength indices, termed requirement equivlencies" of the mterils. thickness index (D) nd thickness "thickness (} re discussed below. equivlencies thickness index (D} is the strength of the pvement bsed on its resistnce deflection cused by wheel lod. It is obtined by the eqution to D lh l+2h 2+ 3h 3 1, 2, nd 3 re the thickness equivlencies of the mterils in the surfce, bse when subbse lyers nd hl, h2, nd h 3 re the thicknesses in inches of the surfce, bse, nd C 51 Trffic in Terms of Vehicles Per Dy. (vpd) conveyed by memorndum dted October from he Deputy Commissioner s Chief Engineer o the Bord of Supervisors of All Counties in he Secondry System. nd DESIGN METHOD FOR FLEXIBLE PAVEMENTS _De sign M eth.o.d Surfce Surfce h 1 Thick. Equiv. l Bse Subbse Subgrde () Three-lyer System (b} Two-lyer System Figure 2. Pvement sections. Thickness Index nd subbse lyers, respectively, s shown in Figure 2. Sometimes subbse my not be provided nd in this cse h 3 0o -4-

7 thickness equivlency () of given mteril is the index of strength mteril contributes per inch depth of the pvement. Its vlue depends on the the thickness equivlencies of the pving mterils re given in Tble 2 6). As new mterils re introduced, their thickness equivlencies hve to (pge evluted. It should be noted tht the thickness equivlencies of some mterils be higher when they re plced in the bse thn when plced in the subbse. Thus re stone hs n vlue of 1o 0 when used in the bse course nd n vlue of untreted in the subbse course. Cement treted ggregte nd select mterils types I 0.6 Investigtions hve shown tht the strength of the cement treted ntive soil borrow mterils (e. g., select mterils type II nd select borrow) vries depending or their physicl nd chemicl properties. For this reson, the thickness equivlencies upon such mterils re kept the sme whether they re plced in the bse or in the sub- of bse. the cse of two-lyer system, the thickness equivlencies of the mteril in In lower lyer will be the sme s tht of the mteril in the bse (given in Tble 2) for the ickness of eight.inches or less. If the thickness of this lower lyer exceeds eight the pvement should be considered s equivlent to three-lyer system with inches, tht it should hve minimum totl thickness of 6 inches nd thickness equiv- re of 1.5. In cse the subgrde soil is very wek or highly resilient (Ro F. 1 or 2) lency _ Thickne.ss Equivlency type of the mteril nd its loction in the pvement. nd IIl re similrly considered. the lower hlf of the bse hving thickness equivlencies equl to those of the subbseo For full-depth sphltic concrete (consisting of n S-5 surfce nd the reminder B-3 bse) plced directly on the prepred subgrde, the tenttive recommendtions the subgrde should be stbilized. -5-

8 EQUIVALENCY VALUES FOR MATERIALS THICKNESS SUBDIVISION ROADS FOR Mteril Mteril Loction Nottion Nottion I 1 Bse Subbse Thick. Equiv Asphltic Concrete (B-3 or B-l) A.C TABLE 2 Loction Vlue 1.67 Surfce 1 Asphltic Concrete (S-5) A.C. Prime nd double sel* D.S. O. 84* 1.50 A. Co (Full dep. Full depth sphlt concrete Untreted Aggregte Agg Cement treted Aggregte CTA 1.67 Selo Mt., Type I &III Sel. Mt Soil Cement S.C Cem. Tr. Selo Mt., Type II Sel. Mt. C 1.17 Cem. Tr. Sel. Borrow Sel. Bor. C 1.00 Untreted Aggregte Agg Cement treted Aggregte CTA 1.33 Sel. Mt., Type I &III Sel. Mt Soil Cement S.C Soil Liin S.L Cem. Tr.Sel. Mt., Type II Sel. Bor. C 1.17 Cem. Tr. Sel. Borrow Sel. Boro C 1.00 * Use this vlue for lh 1 s shown in exmples 1, 2, nd 3 given on pges 11,, nd

9 .Evlu.ti0 n esign Procedure method of evlution of the verge CBR vlue of the project hs been in the preceding pges. explined design CBR vlue is two-thirds of the verge CBR vlue. fctor of is dopted s sfety fctor to compenste for the nonuniformity of soils two-thirds on projects, nd lso to compenste for the very low bering CBR smples encountered re not considered when computing the verge CBR vlues of soils encountered which projects Further, four dys of soking s specified in the test method does on necessrily give the minimum CBR strength of some soils. Thus, the two-thirds not predicted CBR design vlues given in Appendix II (pges A-2 through A-6) be used only with the pprovl of the District Mterils Engineer locted in the cn option of chnging these predicted CBR vlues bsed on his knowledge of locl soil predicted regionl resiliency fctors given in Appendix II (pges A-2 to nd Figure 1 should be used. A-6) Ev..!.u, 0 n of.sol.1 Support Vlue (SSV) Design CBR x R. F. SSV bove. given predicted SSV vlue s given in Appendix II (pges A-2 through A-6) nd in Figure 3 (pge 8 cn be used only when the District Mterils Engineer hs lso trffic count is the trffic in both directions. For two-lne fcilities, the design trffic This equl to this trffic count. For four-lnes, the design trffic is equl to 80% of this is design procedure is s follows- o.f.,design.cbr fctor would compenste for ll such vritions. District Highwy Engineer's Office. District Mterils Engineer will hve the conditions..evl ution. of Re.silienc. Fctor tro.f.) evlutions of the design CBR nd R.F. re pproved the design CBR vlue given in the Appendix. Ev, lu.tion of Design Trffic (Design...VPD) method of determining the trffic count hs been noted in the preceding pges. trffic count. -7-

10 -8-

11 nomogrph (Figure 4, pge ) considers design trffic in both directions. fct tht only hlf the design trffic uses the design lne hs been tken into ccount the development of the thickness index (D)o For this reson, the nomogrph should be in t the design trffic count. entered nomogrph ssumes hevy commercil trucks (2 xles nd 6 tires or hevier) be not greter thn 5.0% of the totl vpd. When it is nticipted tht the trffic will to higher percentge of these hevy trucks the equivlent design vpd will be include s follows. Equivlent design vpd the design vpd + 20 times the number clculted the nomogrph (Figure 4, pge ) t the soft support vlue (SSV) nd Enter trffic (design vpd) vlue nd determine the thickness index (D). design nomogrph specifies minimum D of 6.8 nd mximum D of 20. If the vlue obtined from the nomogrph is greter thn 20, stge construction with D D the vlue of D is obtined, the mteril in ech lyer of the pvement nd After thickness of ech lyer s shown in Figure 2 (pge 4) cn be determined by the the is illustrted by three exmples, given on pges 11,, nd 13, using the dt This below. se exmples re intended to clrify the design procedure nd not given necessrily the pvement design selection. vpd 350, 900, nd 4,000o the clyey soils with no mic content nd where vpd For bove mentioned pvement design stndrds re for flexible pvements only. re minimum requirements, nd where ceunty hs estblished pvement designs se hve greter thickness index, the county's pvement designs shll supersede this which procedure. design of excess hevy commercil trucks over 5.0 percent of the trffic. nomogrph will then be entered t the equivlent design vpd insted of t the design vpd. Evlution o,f,, Thiq,kne.ss In..dex (D) 20 in the first stge my be provided. Choice of Mterils nd ir Thicknesses following eqution: D= lh 1 +2h 2+3h 3 ( ee Figure 2, pge 4) Exmple No. 1 For sndy nd sndy cly soils of the costl plin nd where the VlXt 150, 300, nd 800. Exmple No. 2 For micceous soils or micceous cly silts nd where Exmple No , 500, nd 3,

12 onlea ouo!l!so t x 0 llllliilll I t td Onl A oddn8 I!o8 A88 -

13 o 0 0 o O0 0 0 l )!_t 0 o CI O0 11-

14 o o 0 0 o o o 0 0 o0 o o t co 0 0. o A b 0 r o Lr'x..t ) 0 & -

15 0 0 _t O oj co t, --t _t 0 13-

16 the required thickness index of the pvement hs been determined, the After of mterils nd the thicknesses of the lyers re determined by the pvement choice preprtion of the subgrde should be in ccordnce with the current (A) Deprtment of Highwys' Rod nd Bridge Specifictions. Virgini when stbilized with stbilizing gent such s cement or cceptble This prctice is highly desirble when fesible. lime. Lime or cement stbilized subgrdes provide Lime tretment of high moisture content soil cn be done in lieu of under- (c) when pproprite. In such cses this lime treted lyer is not to be cutting (2) Bse Course percent by weight should be used. In ll cses, however, representtive smples 5 the soil should be submitted for test. of soil stbiliztion (cement or lime) is used, verifiction of the quntity If stbiliztion ctully used will be required through the Highwy District of stbilized subgrdes or subbses re overlin by sphltic concrete, crcks When these courses reflect through the sphlt mix. To prevent this type of reflec- in stbiliztion should be immeditely covered with n un- soil ggregte bse course. treted (A) Aggregte bse courses re of two types nd vrious sizes s shown below: Type I _De sigp Con_sidertions se decisions re usully bsed on dollr vlue, structurl dequcy, designer. pvement servicebility. nd Bsed on design nd construction experience, the following re recommended- (1) S.ubgrde, subgrde tretment, o.r.subbs.e (B) mterils tht normlly would be considered unstisfctory for use Locl construction (like micceous, A-3 type, or swelling soils) my be in rigid foundtion tht is good investment when the trffic is likely to increse considerbly. considered s prt of the pvement structure. When cement stbilized subgrde is recommended, pproximtely per- (D) by volume should be used. When lime is the stbilizing gent, pproximtely cent Mterils Engineer. (E) tion crck n untreted ggregte lyer (minimum of 3-inches thick) lid between stbilized lyer nd the sphltic concrete my be provided. the stbiliztion should be completed before the temperture drops below 40 Fo Soil (F) For best results, bse mteril (crushed mteril only). Aggregte size nos. 20, 21, 21-A, or 22. Aggregte 14-

17 Type II ggregte bse mteril Type I is specified, the When grding corser nos. 20, 21, or 21-A re preferble. ggregtes percentge of (3) Surfce course equivlent thickness of bituminous concrete in lieu of An prime nd double would be prime with cover mteril nd 0 pounds per squre yrd (one sel type designs my be set up where prcticl to provide resonble competition Alternte prctice might ttrct more bids with resultnt economies in construction costs. This gives the concrete slb nd bse thickness for vrious ctegories of it is nticipted tht the trffic will include higher thn norml percentge Where hevy commercil trucks (2 xles 6 tires nd hevier) bove 5 percent six-inch of depth of bse mteril stbilized with 4 provided in Tble 3. In cse of very wek or highly resilient soil, the soil in thickness should be stbilized for depth of 6 inches with percent cement by volume. plce concrete shll be Clss A-3 pving concrete ccording to the current Virgini of Highwys' Rod nd Bridge Specifictions or pproprite supplement Deprtment bse mteril (crushed or uncrushed mteril). Aggregte size nos. 21, 21-A, or 22. Aggregte 21 ggregte bse mteril Type II is specified, ggregte size When nos. 21-A should be selected when commercil mteril is provided. or When it is intended to stbilize locl mteril with cement, pproximtely 8 (B) by volume should be used. When lime is the stbilizing gent, pproxi- percent 4 percent by weight should be used. In ll cses, however, representtive mtely of the mteril should be submitted for test to determine the correct smples stbilizing gent. minimum Bituminous concrete bse courses shll be either Type B-1 (c) B-3. or thickness of the course is 3 inches. lyer inch thick) bituminous concrete, Type S-4 or S-5o (4) Alternte type _design.s DESIGN METHOD FOR PORTLAND CEMENT CONCRETE PAVEMENT Tble 3 design trffic in terms of vehicles per dy. percent cement by weight will replce the bse concrete pvement shll be plin portlnd cement concrete with mximum specifictions. trnsverse joint spcings of 20 feet. 15

18 Design Trffic Slb Thickness Bse Thickness to 400 5" up 750 6" 401 TABLE SLAB AND BASE THICKNESSES FOR DIFFERENT TRAFFIC CATEGORIES 751 to 3,000 7" 4v,, over 3,000 8" 6"* *6-inch soil cement could be substituted for 4-inch or 6-inch bse mteril. 16-

19 K. Vswni. In prepring this guide subcommittee consisting of J. P. N. K. Ho McGhee nd N. K. Vswni ws estblished. Messrs. Bssett Bssett, improve ech sttement mde in this guide. It reflects their enormous work nd nd experience. ACKNOWLEDGMENTS This Design Guide is the end result of the design method developed by nd McGhee worked mny hours nd with gret cre to verify, constntly evlute, study ws conducted under the generl supervision of Jck H. Dillrd, stte highwy reserch engineer, nd ws finnced from stte reserch funds. -17-

21 this evlution, soil clssifictions bsed on AASHO Designtion In snd content (retined #200) nd mic content* hve been - M , determine the soil resiliency fctor, proceed from the top to the To of the tble nd obtin the correct resiliency fctor by the process bottom low resilient soils () A-1 nd A-3 soils Very A-2, A-4, A-5, A-6 (b) Ao7 soils with nd content 60 or snd resilient soils A-2, A- t, A-5, A-0 nd A-7 Low with snd content more soils 40 nd less thn 60 per- thn cent low resilient soils A-2, A-4, A-5, A-6 nd Medium soils with snd con- A-7 low resilient soils () A-7-5 soil Medium A-4 soil with low (b) content* nd mic n verge group with (G. I. below 5. index A-2, A-5, A-6 nd A-7-6 (c) with low (including soils mic content trces) resilient soils Soils which do not come within the High of "medium low resilient ctegory RESILIENCY FACTOR of the mic content is to be done by visul observtions. *Determintion borderline cses of low or high mic content will be decided by the APPENDIX I EVALUATION OF SOIL RESILIENCY FACTORS dopted. of elimintion. SOIL TYPE Soils without mic content more percent tent 40 percent or less Soils with mic content (including trces) soils" nd lso contin mic. District Mterils Engineer of the Virgini Highwy Deprtment.

22 County or Town Arlington W. of Rte. 95 O0 of Rte. 95 E. E. of Rte. 29 Albemrleof Rte. 29 W. Alleghny Ameli Botetourt- bulge in the Ii rock, estern Buckinghm Cmpbell wy up to hlf Rock. Egle Croline W. of Rte of Rte. 2 E Soil Support (SSV) Vlue Fctor x APPENDIX II CLASSIFICATION BASED ON RESILIENCY AND CBR VALUES OF SOILS Code (Res. Resiliency Design Fctor CBRVlues C BR) 01 Accomck O Amherst Appomttox 07 August 2 6 O8 Bth O9 Bedford Blnd Reminder ofcounty Brunswick Buchnn Crroll Chrles City

23 County or Town S.W. Mosley Chesterfield Colonil nd 15S nd of Rtes. 229 W. Firfx E. of Rte of Rte. 95 W. Resiliency Design Soil Support (SSV) Vlue Fctor x 21 4 Ii APPENDIX II (continued) Code (Res. Fctor C BR) C BR Vlues 19 Chrlotte Chespeke 2O Heights r of county Reminde Clrke 21 Crig 22 Culpeper- E. of Rtes nd 15S 24 Cumberlnd 25 Dickenson 26 Dinwiddie Essex Fuquier N. of Rte O of Rte. 211 S. Floyd 31 Fluvnn Frnklin 34 Frederick 35 Giles 14 Gloucester 3.0 3O 36 W. Rte. 522 Goochlnd- Rte. 522 E Gryson 38 Greene 39 E. Rte. 95 Greensville Rte. 95 W. 4O

24 Rte. 95 nd W. Rte. 715 E. Henrico- W. Rte Rte. 95 E. George King nd Queen King King Willim Loudoun- W. Rte Rte. 15 E. Mecklenburg Middlesex Montgomery Nnsemond Resiliency Design 6 Fctor x APPENDIX II (continued) Soil Support.Vlue (SSV) (Res. Fctor C ode County o r Town C BR Vlues CBR) 41 Hlifx Hmpton 114 Hnover E. Rte W. Rte Henry 44 Highlnd 45 Isle of Wight 46 Jmes C ity O 3O 51 Lncster 52 Lee 6 54 Louis Lunenberg 55 Mdison Mthews 3.0 i0 3O O Nelson 63 New Kent 27 1 Newport News 27

25 County or Town Northmpton Northumberlnd of Rte. 20 nd N. Rte. 522 W. of Rte. 20 nd S. Rte. 522 E. of Rte. 20 nd S. Rte. 522 W. Pittsylvni W. Rte. 522 nd Powhtn- Rpphnnock- N. 609 Rte. Rte. 522nd E. W. Jmes, Mury, Rockbridge-- South Rivers nd Jmes, Mury, E. South Rivers nd Resiliency Design Soil Support (SSV} Vlue Fctor x (continued) APPENDIX II Code Fctor C BR Vlues (Res. C BR} 2 Norfolk O 66 Nottowy 68 N. of Rte. 20 nd Ornge- Rte. 522 E. Pge- W. Alm E. Alm 8 1 Ptrick Rte. 609 Prince Edwrd George Prince Willim- W. Rte. 95 Prince E. Rte. 95 Pulski 78 Flint Hill S. Flint Hill 3O 79 Richmond 8O Ronoke 14 81

26 County or Town Southmpton W. Rte. 95 Spotsylvni- Surry Sussex--W. Rte Wshington Westmorelnd Resiliency Design Soil Support (SSV) Vlue Fctor x (continued) APPENDIX II Code (Res. C BR Vlues Fctor CBR) W. Rte. 81 Rockinghm Rte. 81 E Russell Scott Shenndoh 86 Smyth E. Rte. 95 Stfford- W. Rte Rte. 95 E O 27 E. Rte Tzewell Virgini Bech- N. Rte Rte. 44 S Wrren O Wise Wythe 98 York 99 21

631 ALLOWANES AND TOLERANCES

631 ALLOWANES AND TOLERANCES ANSI Fits. Tbles 3 through 9 inclusive show series of stndrd types nd clsses of fits on unilterl hole bsis, such tht the fit produced by mting prts in ny one clss will produce