1、ASCE STANDARDASCE/TZR= standard normal deviate for reliability R;S0= overall standard deviation;SN = structural number of the pavement, calculated asPaidi,whereai= structural layer coefcient per layer i;di= layer thickness per layer i;pi= initial serviceability;pt= terminal serviceability; andMR= su
2、bgrade resilient modulus (units must be U.S. customary).3.3 DESIGN LIFEThe design life of a pavement is the intended years of servicefrom the pavement structure before major rehabilitation. Majorrehabilitation typically consists of removal of the pavers andbedding sand layer, repairs to the base mat
3、erial and drainageimprovements, and replacement of the bedding sand and pavers.Rehabilitation is typically required to address shear failure of thebedding sand, base, subbase, or subgrade soils, typically indicat-ed by surface deformation from wheel loads or settlements.Surface distresses, severity,
4、 and extent can be assessed usingASTM E2840, Standard Practice for Pavement Condition IndexSurveys for Interlocking Concrete Roads and Parking Lots(ASTM 2011). Design life in this standard guideline is expressedas the pavement structure required to accommodate the designednumber of ESALs.3.4 DESIGN
5、RELIABILITYThe reliability design concepts are generally incorporated intothe way the pavement designer assembles pavement designinputs. For the AASHTO (1993) design procedure, the higherthe selected reliability and standard deviation, the higher thedesign ESALs used in the design. The effect of the
6、 reliability andstandard deviation are factored from the actual ESALs using thefollowing equation:logdesign ESALs= logactual ESALsZRS0(3-2)For this standard guideline, a constant reliability level of 75%ZR= 0.67 and standard deviation of 0.45 have been selected.This represents a low-to-medium reliab
7、ility level, which istypical for low-speed municipal roadways. Using Eq. (3-2) andan actual ESAL value of 1 million, the reliability function of theAASHTO (1993) design equation would result in a factoredESAL value of 2 million. If a higher reliability value, say 90%ZR= 1.28, were input into Eq. (3-
8、2), a factored ESAL value ofabout 3.75 million would result.3.5 DESIGN TRAFFICThe amount of damage caused by trafc loading will depend onthe number and type of vehicles that pass over the pavementsection. Trafc design loading for the AASHTO (1993) designprocedure is represented using the ESAL concep
9、t. One ESAL isrepresented as the impact from a single 80-kN (18,000-lb) axleload.Conversion of the trafc ESALs into the trafc index (TI) usedin California is accomplished as follows:Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways 5TI=9.0C18ESAL106C190.119(3-3)F
10、or this standard guideline, ESAL levels are provided for 10typical levels of municipal trafc up to a maximum of 10 millionESALs (see Table 4-1). The designer needs to select the appro-priate trafc level and design life. The typical initial design lifefor municipal pavements is 2040 years.3.6 SUBGRAD
11、E SOIL STRENGTHING ASSESSMENTSubgrade conditions should be assessed for all pavement designs.The soil strength is evaluated specically for each project andshould be tested in accordance with the appropriate ASTM orAASHTO method or other local standard. Typically, the resilientmodulus determined by A
12、ASHTO T-307 (AASHTO 2004a) isused to describe the strength of the subgrade soil. This can bedetermined directly from laboratory testing or through surrogatessuch as the California Bearing Ratio (CBR), as determined byASTM D1883 (ASTM 2007) tests. The soil should be tested inthe moisture condition ex
13、pected during the lifetime of thepavement. In most cases, except for in arid regions, this is asaturated (or soaked) condition. If it is not possible to performlaboratory tests, typical resilient modulus values based on theUnied Soil Classication System are available.This standard guideline uses eig
14、ht categories of subgradequality, ranging from good-quality gravels and rock with excel-lent drainage to poor-quality clay materials that are semi-impervious to water. Subgrade types are classied according tothe Unied Soil Classication System, as outlined in ASTMD2487 (ASTM 2006a). Values in Table 3
15、-1 are provided forguidance only. When laboratory tests are unavailable, Table 3-1should be used to select the appropriate category. Typical resil-ient modulus values with corresponding R-values and CBRs forthe eight soil categories are provided in Chapter 4.3.6.1 Characterizing Subgrade Drainage. O
16、nce the generalsubgrade type has been selected, the engineer should identify thedrainage quality of the subgrade. Depending on the type ofsubgrade, the strength of the pavement can be reduced if thereis excess water in the subgrade. This standard guideline includesan adjustment to the resilient modu
17、lus of the subgrade based onthe overall quality of the pavement drainage as shown inTable 3-2. The impact of water on the resilient modulus ofthe subgrade can be improved by limiting the subgrade exposureto water by ensuring that the pavement structure is well drainedusing drainage layers, ditches,
18、or underdrains.3.6.2 Frost,SwellingSoils,andOtherConsiderations. Subgradeswelling and frost heave can affect the performance of a municipalEstimate ESALs(or TI) from projected traffic mix (3.5)Characterize subgrade strength as Category 18 (3.6)Characterize subgrade drainage as good, fair, or poor (3
19、.6.1) Select base materials and thicknesses from charts Unbound dense-graded base: 100150 mm (46 in.) (3.7.1) Bound bases:100-mm (4-in.) thick ATB 100-mm (4-in.) thick CTB 100 to 150-mm (4 to 6-in.) thick aggregate base (3.7.2) Begin design Select unbound dense-graded subbase thickness of 150 mm (6
20、in.) or greater from tables (4.1) Select geotextile(3.10) Select joint and bedding sand, bedding sand drainage (3.11)Design pavement structure drainage (3.9) Prepare construction details, drawings, and specifications (3.14) Select concrete paver and laying pattern (3.12.1) OR Select design reliabili
21、ty (3.4) Figure 3-1. Design process owchart; numbers in parentheses refer to sections of this standard guidelineNote: ATB=asphalt treated base, CTB=cement treated base.6 STANDARD 58-16pavement and should be considered as appropriate for localconditions. Frost and swelling may be reduced or eliminate
22、d byremoval and replacement of subgrade soil materials with less frost-susceptible soils. Frost heave may also be mitigated by improvingdrainage conditions and/or by providing a non-frost-susceptiblelayer. Swelling may also be mitigated by stabilizing the subgradewith additives such as lime or cemen
23、t.3.7 SELECTION OF BASE MATERIALS ANDTHICKNESSESThe next step in the design process is to select the type of basematerial that will be used for the pavement. This standardguideline supports the use of bound (treated) and unbound bases.Untreated aggregate base and subbase should be compacted to atlea
24、st 98% of maximum dry density based on AASHTO T180Method D (AASHTO 2009) or the equivalent.3.7.1 Unbound Dense-Graded Base. Aggregates should becrushed, angular materials. Crushed aggregate bases used inhighway construction are generally suitable for interlockingconcrete pavement. Unbound base mater
25、ials should meet localstate, provincial, or municipal standards governing basematerials. Recycled aggregates may be used, but they mustmeet the same conditions as specied for nonrecycledaggregates and, as appropriate, be mixed in proportion withnonrecycled aggregates according to recommendations fro
26、mlocal, state, or provincial transportation agencies. When localspecications are unavailable, the base material should meet thegradation requirements of ASTM D2940 (ASTM 2009b).Unbound base materials should have a maximum loss of 60%when tested in accordance with Canadian Standards Association(CSA)
27、A23.2-29A (CSA 2004b) and a maximum loss of 40%when tested in accordance with ASTM C131 (ASTM 2006d) orCSA A23.2-17A (CSA 2004b). The plasticity index should be amaximum of 6 and the liquid limit should be a maximum of 25when they are tested in accordance with ASTM D4318 (ASTM2005a) and AASHTO T89 a
28、nd T90 (AASHTO 2002, 2004b).For constructability purposes, the minimum design unbound basethickness should be 100 mm (4 in.) for less than 500,000 ESALsand 150 mm (6 in.) for 500,000 or more ESALs.3.7.2 Bound (or Treated) Bases. Asphalt-treated base (ATB)and cement-treated base (CTB) materials and i
29、nstallation shouldconform to state, provincial, or municipal specications for adense-graded, compacted asphalt concrete. ATB material shouldhave a minimum Marshall stability of 8,000 N (1,800 lbs), perASTM D5 (ASTM 2006b) and AASHTO T49 (AASHTO 2007).Use of the appropriate asphalt cement binder for
30、local climateconditions is recommended. CTB material should have aminimum 7-day unconned compressive strength of 4.5 MPa(650 psi), per ASTM D4320 (ASTM 2009a) and D4219 (ASTM2008b). For constructability and design purposes, the minimumbound base thickness should be 100 mm (4 in.).3.8 DETERMINING SUB
31、BASE THICKNESSThe required subbase thickness is determined using the designreliability, design life (as reected by design trafc), estimatedtrafc, subgrade soil type, pavement structure drainage, and basetype selected.3.8.1 Unbound Dense-Graded Subbase. Aggregates shouldbe crushed, angular materials.
32、 Crushed aggregate bases usedin highway construction are generally suitable for interlockingconcrete pavement. Unbound subbase materials should meet thelocal state, provincial, or municipal standards governing subbasematerials. When local specications are unavailable, the subbaseshould meet the grad
33、ation requirements of ASTM D2940(ASTM 2009b). The plasticity index should be a maximum of10, and the liquid limit should be a maximum of 25, according toASTM D4318 (ASTM 2005a) and AASHTO T90 (AASHTO2004b). Subbase thicknesses should be chosen from the designtables provided in Chapter 4. For constru
34、ctability purposes, aminimum unbound subbase design thickness of 150 mm (6 in.)should be used.3.9 DESIGN PAVEMENT STRUCTURE DRAINAGEThe design should consider drainage of the bedding sand layerand the soil subgrade. Fig. 3-2 is the typical drainage detail forTable 3-1. General Soil Categories and Pr
35、opertiesCategory numberUnied SoilClassicationaBrief descriptionDrainagecharacteristicsSusceptibility tofrost action1 Boulders/cobbles Rock, rock ll, shattered rock, boulders/cobbles Excellent None2 GW, SW Well-graded gravels and sands suitable as granular borrow Excellent Negligible3 GP, SP Poorly g
36、raded gravels and sands Excellent to fair Negligible to slight4 GM, SM Silty gravels and sands Fair to semi-impervious Slight to moderate5 GC, SC Clayey gravels and sands Practically impervious Negligible to slight6 ML, MI Silts and sandy silts Typically poor Severe7 CL, MH Low plasticity clays and
37、compressible silts Practically impervious Slight to severe8 CI, CH Medium to high plasticity clays Semi-impervious toimperviousNegligible to severeaASTM (2006a).Note: G (gravel), S (sand), M (silt), C (clay), O (organic), P (poorly graded), W (well graded), H (high plasticity), L (low plasticity).Ta
38、ble 3-2. Pavement DrainageQuality of drainage Time to drain Soil category numberaGood 1 day 1, 2, 3Fair 7 days 3, 4Poor 1 month 4, 5, 6, 7, 8aFrom Table 3-1.Structural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways 7Figure 3-2. Drainage detail with aggregate base/subbase
39、Figure 3-3. Drainage detail for pavers over treated base8 STANDARD 58-16untreated bases. For treated bases, bedding sand layer drainage istypically accomplished by providing vertical drainage at thelowest elevations, as shown in Fig. 3-3. Fig. 3-4 is a typicaldrainage detail for catch basins or util
40、ity structures with treatedbases.All drainage outlets should be covered with geotextile toensure that the design prevents migration of bedding sand intothe drainage system. For unbound bases, the geotextile shouldextend 300 mm (12 in.) from the pavement edge, as shown inFig. 3-2. For treated bases,
41、the geotextile should be used fullwidth, on top of the treated base, to prevent migration of thebedding sand through cracks and joints. In all cases, the geo-textile should extend vertically upward to the top of the pavementat all curbs or collars.The design should consider drainage of the base and
42、soilsubgrade as this benets pavement life and performance. Place-ment of perforated drain pipe and/or edge drains should conformto local practices.3.10 GEOTEXTILEThe engineer should review the need for a geotextile to separatethe subgrade soil from the pavement structure or to preventbedding sand mi
43、gration into lower layers or laterally throughdiscontinuities such as control joints and saw cuts.Separation geotextiles should be used to prevent the mixing ofsubgrade soil and base/subbase material. The designer willtypically require a woven fabric with a minimum equivalentopening size of 300 m to
44、 a maximum of 600 m (0.0120.024 in.). The engineer should reference AASHTO M288,Standard Specication for Geotextile Specication for HighwayApplications (AASHTO 2006), to specify the appropriate geo-textile. If weak or wet/saturated subgrade conditions exist, ageotextile with stabilizationandltration
45、capabilities may also berequired.3.11 BEDDING AND JOINT SAND REQUIREMENTSProper selection of bedding and joint sands is of paramountimportance to the function of an interlocking concrete pavement.The bedding layer should be nominally 25 mm (1 in.) inthickness before compaction for all designs.3.11.1
46、 Bedding Sand. Bedding sand should be well graded,conforming to the particle-size distribution requirements ofASTM C33 (ASTM 2008a) or CSA A23.1 (CSA 2004a),except that the amount passing the 75 m (No. 200) sieveshould preferably be limited to a maximum of 1%. Sands withpredominant silica geologies
47、and subangular to subroundedparticle shape have shown excellent performance. For vehicularFigure 3-4. Drainage detail at a catch basin for treated baseStructural Design of Interlocking Concrete Pavement for Municipal Streets and Roadways 9applications exceeding 1.5 million lifetime ESAL repetitions
48、or aTI greater than 9.4, the bedding sand should also be tested forpermeability, degradation, and durability before selection.The following test methods, among others, have shown to begood indicators of bedding sands for vehicular applications:ASTM C88, “Standard test method for soundness of aggrega
49、tesby useof sodium sulfateormagnesium sulfate” (ASTM2005b);CSA A23.2-23A, “Method of test for the resistance of neaggregate to degradation by abrasion in the micro-devalApparatus” (CSA 2004b); ASTM D7428, “Standard testmethod for resistance of ne aggregate to degradation byabrasion in the micro-deval apparatus” (ASTM 2015); andASTM D2434, “Standard test method for permeability ofgranular soils (constant head)” (ASTM 2006c). See Interlock-ing Concrete Pavement Institute (ICPI) Tech Spec 17,“Selection of bedding sands for interlocking concrete p
