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3 CHAPTER 2. SYNTHESIS OF CURRENT KNOWLEDGE This chapter presents the results of the literature review conducted on the causes of the problems pointed out in Chapter 1 and current solutions that target the identified causes. The answers to these two questions are organized as follows: ï· Review the characteristics of unbound layers and subgrade used in the AASHTOWare Pavement ME Design software and MEPDG. ï· Collect and review the influence of unbound layer and subgrade characteristics on the performance of flexible and rigid pavements. ï· Collect and identify ME models of unbound layers and subgrade that address such influence. CHARACTERISTICS OF UNBOUND LAYERS AND SUBGRADE USED IN PAVEMENT ME DESIGN The AASHTOWare Pavement ME Design software and MEPDG are practical tools for the pavement design and analysis based on ME principles. They predict multiple performance indicators for flexible and rigid pavements, including the following (1): ï· Flexible pavements: o Total rut depth of the asphalt layers, aggregate base, and subgrade. o Load-related cracking (alligator cracking and longitudinal cracking). o Thermal cracking. o Smoothness (International Roughness Index [IRI]). ï· Rigid pavements: o Transverse cracking in jointed plain concrete pavement (JPCP). o Faulting in JPCP. o Punchouts in continuously reinforced concrete pavement (CRCP). o Crack spacing and crack width in CRCP. o Smoothness (IRI) in JPCP and CRCP. For each performance indicator above, Pavement ME Design has a distress prediction model that requires inputs from different layers in a pavement structure. Table 1 shows the inputs from unbound layers and subgrade to account for the influence of these underlying layers.
4 Table 1. Inputs from Unbound Layers and Subgrade in Pavement ME Design. Performance Indicator Input Parameters Unbound Layers Subgrade Fl ex ib le P av em en t Total Rut Depth MR Thickness Poissonâs ratio Soil water characteristic curve (SWCC) MR Percent passing No. 200 SWCC Poissonâs ratio Load-related Cracking (alligator and longitudinal cracking) MR Thickness Poissonâs ratio SWCC MR Liquid limit Percent passing No. 200 Poissonâs ratio Groundwater depth SWCC Plasticity index Thermal Cracking MR Thickness Poissonâs ratio SWCC MR Percent passing No. 200 SWCC Poissonâs ratio Smoothness (IRI) MR Thickness MR Percent passing No. 200 SWCC R ig id P av em en t Transverse Cracking (JPCP) Thickness MR Erodibility index Loss of friction Groundwater depth MR Faulting (JPCP) MR Erodibility index Thickness Load transfer efficiency (LTE) MR Punchouts (CRCP) MR Base slab friction Thickness MR Groundwater depth Crack Width (CRCP) Base slab friction MR Thickness LTE MR Groundwater depth Smoothness (IRI) (JPCP) MR Erodibility index Base slab friction Thickness MR Smoothness (IRI) (CRCP) MR Base slab friction Thickness MR
5 However, recent investigations indicate that the performance predicted by Pavement ME Design generally shows low or no sensitivity to these underlying layers. A recent study conducted in the NCHRP Project 01-47 (2) reveals the following major problems: ï· Total rutting in flexible pavements is marginally sensitive to MR and SWCC of unbound layers and subgrade, non-sensitive to thickness of unbound layers. ï· Load-related cracking in flexible pavements is non-sensitive to the SWCC of unbound layers, marginally sensitive to SWCC of subgrade. ï· Faulting in JPCP is marginally sensitive to MR and erodibility, non-sensitive to the thickness of unbound layers. ï· Transverse cracking in JPCP is marginally sensitive to MR, thickness, and erodibility of unbound layers. To find the reasons for these problems, a better understanding of how the properties/thickness of unbound layers and subgrade affect pavement performance is needed, and this is detailed next. INFLUENCE OF UNBOUND LAYERS AND SUBGRADE ON PERFORMANCE OF FLEXIBLE AND RIGID PAVEMENTS Table 1 presents the inputs of unbound layers and subgrade required in Pavement ME Design for predicting the performance of flexible and rigid pavements. However, besides these parameters, recent studies have identified the pavement performance to be significantly affected by other characteristics of the underlying layers. According to a comprehensive literature review, researchers divided the factors into the following categories: ï· Material properties (e.g., modulus, shear strength). ï· Material behaviors responding to traffic and environmental (temperature and moisture) conditions (e.g., permanent deformation and erosion). ï· Structural characteristics (e.g., thickness of unbound layers). Table 2 to Table 5 summarize how each performance indicator is influenced by the factors of unbound layers and subgrade. The relevant literature is also given in these tables. Elaborated explanations for Table 2 to Table 5 are presented in Appendix A, âAnnotated Bibliography of Influence of Unbound Layers and Subgrade.â
6 Table 2. Influential Factors of Unbound Layers on Performance of Flexible Pavements. Pe rf or m an ce  In di ca to rs  Material Properties Material Behaviors Thickness Modulus Shear Strength Permanent Deformation Magnitude CrossâAnisotropy Moisture Sensitivity To ta l R ut tin g Total rutting decreases as modulus increases (3, 4) The amount of permanent deformation significantly increases when anisotropic properties are used (5) Modulus has a high sensitivity in change of matric suction that represents moisture susceptibility; high degree of moisture causes decrease of the modulus (15â19) Shear strength directly affects total rutting; it decreases as shear strength increases (6â11) Total rutting increases as permanent deformation of unbound base course increases (12) Rutting decreases with increase of the thickness of the base layer (4) Lo ad âr el at ed  C ra ck in g (A lli ga to r a nd  Lo ng itu di na l) Loadârelated cracking would easily occur with reduced modulus (4, 12) Use of crossâ anisotropy of unbound base course results in less estimated fatigue cracking life (13) A larger shear strength improves the integrality of supporting layers and also resistance to loadârelated cracking (1)  N/A The resistance to loadâ related cracking would be enlarged with thick unbound layers (3, 4) Th er m al  C ra ck in g Thermal cracking is accelerated by loss of modulus (14) N/A N/A N/A The greater thickness of the base layer possibly helps alleviate the severity of thermal cracking (20) Sm oo th ne ss  (I RI ) IRI decreases with the increase of base modulus (4) Crossâ anisotropy affects total rutting and cracking, which leads to the change of IRI (4) High shear strength results in low IRI values (1, 11) Permanent deformation of unbound base is a major distress resulting in increase of surface roughness (9) Change of IRI diminishes with increase of thickness of the base layer (4)
7 Table 3. Influential Factors of Unbound Layers on Performance of Rigid Pavements. Pe rf or m an ce  In di ca to rs  Material Properties Material Behaviors Thickness Modulus Shear Strength Erosion Permanent Deformation Magnitude CrossâAnisotropy Moisture Sensitivity Tr an sv er se  C ra ck in g (JP CP ) Transverse cracking would be promoted with low modulus of unbound layers (3, 21) Crossâ anisotropy greatly affects stress/ strain and cracking (5, 13)  Modulus has a high sensitivity in change of matric suction that represents moisture susceptibility; high degree of moisture causes decrease of the modulus (14, 19, 31) High shear strength prevents occurrence of transverse cracking (22, 23)  N/A N/A Thickness of baser layer directly affects amount of transverse cracking (3) Fa ul tin g (JP CP ) Loss of modulus of unbound base course lead to development of faulting (24) N/A Increase of shear strength inhibits the development of faulting (24) Development of erosion accelerates faulting (24â 26) Greater permanent deformation of unbound base leads to higher potential of faulting (27) Faulting decreases with high base thickness (3) Pu nc ho ut s ( CR CP ) Reduction of modulus of unbound base course causes punchouts (28â30) N/A Potential for punchouts is greater when shear strength decreases (25, 28) Erosion intensifies punchout (25, 28, 32) N/A Increase of thickness is an effective method to control punchouts (3) LT E (JP CP  a nd  CR CP ) A higher modulus of unbound base layer improves LTE (25, 33)  N/A Unbound layers with high shear strength have good LTE (24) Development of erosion causes low LTE (25,  34) N/A Increase of thickness helps improve LTE (25) Sm oo th ne ss  (I RI ) (JP CP  a nd  C RC P)  IRI decreases with increase in modulus of base layer (3) Crossâ anisotropy affects cracking and so IRI (5, 13) Increase of shear strength of base layer diminishes roughness (35, 36) Erosion aggravates IRI (25,  34, 37) Permanent deformation of unbound base increases roughness (9) IRI decreases with increase in base layer thickness (3)
8 Table 4. Influential Factors of Subgrade on Performance of Flexible Pavements. Pe rf or m an ce  In di ca to rs  Material Properties Material Behaviors Modulus Shear Strength Permanent Deformation Magnitude CrossâAnisotropy Moisture Sensitivity To ta l R ut tin g Total rutting decreases as modulus increases (18) Use of nonlinear anisotropic model of subgrade affects stress/strain distribution, and then influences the inputs in distress prediction models (5, 38, 39) A higher soil suction generates a larger modulus of subgrade (40â45) Total rutting decreases as shear strength of subgrade increases (46) Total rutting increases as permanent deformation of subgrade augments (46) Lo ad âr el at ed  Cr ac ki ng  (A lli ga to r a nd  Lo ng itu di na l) Resistance to loadârelated cracking would be enhanced with increase of modulus of subgrade (2, 3, 18) N/A Lower permanent deformation of subgrade reduces the probability of loadârelated cracking (39) Th er m al  C ra ck in g N/A N/A N/A N/A Thermal cracking is related to shrinkage of supporting subgrade soils; high permanent deformation would reduce the resistance to thermal cracking (14) Sm oo th ne ss  (I RI ) IRI has a negative relation with modulus of subgrade (4, 47) Use of nonlinear anisotropic model of subgrade affects stress/strain distribution, and then influences the inputs in distress prediction models (5, 38, 39) Soil suction is a major factor for prediction of subgrade modulus (41) Decrease of shear strength of subgrade results in loss of smoothness (1) High permanent deformation exacerbates the roughness of pavement (9, 14)Â
9 Table 5. Influential Factors of Subgrade on Performance of Rigid Pavements. Pe rf or m an ce  In di ca to rs  Material Properties Material Behaviors Modulus Shear Strength Permanent Deformation Magnitude CrossâAnisotropy Moisture Sensitivity Tr an sv er se  C ra ck in g (JP CP ) Increasing modulus of subgrade would reduce transverse cracking (3, 21) Crossâanisotropy affects stress/strain and then influences the inputs in distress prediction models (5, 13) Soil suction is a major factor for the prediction of modulus of subgrade materials; a higher soil suction generates a larger modulus of subgrade (41) Increase of shear strength of subgrade raises the resistance of transverse cracking (1) High permanent deformation leads to loss of supporting layers, which could cause development of transverse cracking (1) Fa ul tin g (JP CP ) Increase in modulus of subgrade causes a decrease in faulting (48) Higher shear strength of subgrade layer helps improve resistance to faulting (27) High permanent deformation of subgrade increases the possibility of faulting (1, 49) Pu nc ho ut s ( CR CP ) Punchout increases with low kâvalue of subgrade (28, 29) N/A Punchout is accelerated with lower shear strength of subgrade (28) Increase of permanent deformation of subgrade makes poorer LTE; thus leads to development of punchouts (49) LT E (JP CP  a nd  CR CP ) LTE is increased by high modulus of subgrade (25) N/A Increase of shear strength improves LTE (25) Loss of LTE occurs with high permanent deformation of subgrade (28) Sm oo th ne ss  (I RI ) (JP CP  a nd  C RC P)  IRI value diminishes with the increase in subgrade modulus (3) Crossâanisotropy affects cracking/faulting and so IRI (5, 13) Improvement of shear strength of subgrade layer could increase smoothness (36) Rutting generated from permanent deformation of subgrade is associated with increased roughness (9)Â
10 UNBOUND LAYER AND SUBGRADE MODELS FOR PERFORMANCE INFLUENCE Table 2 to Table 5 demonstrate various characteristics of unbound layers and subgrade that affect the performance of flexible and rigid pavements. Based on these results, researchers searched and identified the ME models that address such influence. More details of each model and associated parameter definitions are given in Appendix B, âDefinitions of Model Parameters of Unbound Layer and Subgrade Models.â More specifically, the relevant models contain the following, which are summarized in Table 6 to Table 11: ï· Unbound layer models: o Current Pavement ME Design models for the base course of both flexible and rigid pavements. o Modulus models (Table 6), particularly those that incorporate the effects of the level of moisture in addition to the traffic-related stresses. The anisotropy of the base course is reflected in a separate model for the vertical modulus and the horizontal modulus. o Permanent deformation models (Table 7), which are sensitive to the changes of properties and thickness of the base course, and particularly the ones that predict a larger range of deformation that is close to the behavior of real unbound layer materials. o Shear strength models (Table 8), especially those models that include the effects of moisture and traffic-related stresses on the shear strength of the base course. o Erosion and faulting models (Table 9). o Thickness sensitive models (Table 11). This category refers to the models that have an influence on the thickness of the base course, which further affects the performance of the pavement. The moisture-sensitive, stress-dependent, and cross- anisotropic modulus models; moisture-sensitive shear strength models; stress- dependent ME permanent deformation models; and ME erosion models could contribute to this category. ï· Subgrade models: o Current Pavement ME Design models for the subgrade of both rigid and flexible pavements. o Modulus models (Table 6), particularly those that incorporate the effects of the level of moisture in addition to the traffic-related stresses on the stiffness of the subgrade. o Permanent deformation models (Table 7), especially those that predict a larger range of deformation that is close to the behavior of real soils. o Shear strength models (Table 8), particularly the ones that include the effects of moisture and traffic-related stresses on the shear strength of the subgrade. This property becomes important when attempting to reflect the performance of a pavement under heavy load, on a moisture-susceptible soil, or where there is poor drainage or there is slippage between the base course and subgrade on which it rests. o Foundation models (Table 10) that significantly reduce errors and variations of critical rigid pavement responses.
11 Table 6. Modulus Models of Unbound Layers and Subgrade. Model Type Model Formulation (detailed definitions of parameters in Appendix B) Material Type Literatures Nonlinear Stress- dependent Model 2 1 3 k RM k ï³ï½ Granular Base (50) Nonlinear Stress- dependent Model 2 1 k RM k ï±ï½ Granular Base (51) Nonlinear Stress- dependent Model ï¨ ï©2 3 1R dM k k k ï³ï½ ï« ï 1 dk ï³ï³ ï¨ ï©2 4 1R dM k k kï³ï½ ï« ï 1 dk ï³ï¼ Subgrade Soil (52) Nonlinear Stress- dependent Model ' ' d R d a bM ï³ ï³ ï« ï½ Subgrade Soil (53) Nonlinear Stress- dependent Model 32 1 kk R dM k ï± ï³ï½ Granular Base/ Subgrade Soil (54) Nonlinear Stress- dependent Model 2 3 1 1 k k oct R IM k Pa Pa Pa ï´ï¦ ï¶ ï¦ ï¶ï½ ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base/ Subgrade Soil (55) Nonlinear Stress- dependent Model 2 3 1 1 1 k k oct R IM k Pa Pa Pa ï´ï¦ ï¶ ï¦ ï¶ï½ ï«ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base/ Subgrade Soil (15) Nonlinear Stress- dependent Model 2 1 2 R I JM M Pa R Pa Pa ï¬ ï© ï¹ï¦ ï¶ï½ ï´ ï«ïª ïºï§ ï· ï¨ ï¸ïª ïºï« ï» Granular Base (56) Moisture-sensitive Model ï¨ ï© log 1 exp ln R Ropt m opt M b aa bM k S S a ï ï½ ï« ïï© ï¹ï« ï« ïïª ïºï« ï» Granular Base/ Subgrade Soil (57) Moisture-sensitive and Stress- dependent Model ï¨ ï© ï¨ ï©2 3 1R d s a wM k k k k u uï³ï½ ï« ï ï« ï ï¨ ï© ï¨ ï©2 4 1R d s a wM k k k k u uï³ï½ ï« ï ï« ï Subgrade Soil (58) Moisture-sensitive and Stress- dependent Model 2 3 1 4 1 3 k koct R I kM k Pa Pa Pa ï´ïï¦ ï¶ ï¦ ï¶ï½ ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base/ Subgrade Soil (59) Moisture-sensitive and Stress- dependent Model 2 3 1 1 3 k km oct R I fhM k Pa Pa Pa ï± ï´ïï¦ ï¶ ï¦ ï¶ï½ ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base/ Subgrade Soil (60) Moisture-sensitive and Stress- dependent Model 2 3 1 1 1 3 3 k km oct oct R II f h M k Pa Pa Pa ï± ï¢ ï¡ï´ ï´ ï© ï¹ï¦ ï¶ï ï« ï«ï§ ï·ïª ïº ï¦ ï¶ï¨ ï¸ïª ïºï½ ï§ ï· ï¨ ï¸ïª ïº ïª ïºï« ï» Granular Base/ Subgrade Soil (14) Moisture-sensitive and Stress- dependent Model ï¨ ï© 21 k R d w mM k ï³ ï£ ï¹ï½ ï« Subgrade Soil (41)
12 Moisture-sensitive and Stress- dependent Model 2 3 1 1 k k w m oct R a a a M k P P P ï± ï£ ï¹ ï´ï¦ ï¶ ï¦ ï¶ï« ï½ ï«ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Subgrade Soil (61) Moisture-sensitive and Stress- dependent Model ' 2 4 4 ' 1 3 1 1o k k k m mnet w sat oct R a a a a uM k P P P P ï¹ ï¹ï± ï´ï ï ïï¦ ï¶ ï¦ ï¶ ï¦ ï¶ï ïï½ ï« ï«ï§ ï· ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ ï¨ ï¸ Granular Base (19) Moisture-sensitive and Stress- dependent Model ï¨ ï© 2 3 6 1 7 3 k k b oct R a us a a w a a kM k p k k p p p ï«ï³ ï´ ï ï ï¦ ï¶ ï¦ ï¶ï ï½ ï« ï« ï ïï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Subgrade Soil (18) Moisture-sensitive and Stress- dependent Model 2 3 4 1 3 1 k k w oct R a a a k SVM k P P P ï± ï´ï¦ ï¶ ï¦ ï¶ï« ï½ ï«ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base/ Subgrade Soil (62) Stress-dependent and Cross- anisotropic Model 2 3 1 1 1 ; k k V oct R a a a H R VH V V R R IM k P P P M Gn m M M ï´ï¦ ï¶ ï¦ ï¶ ï½ ï«ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ ï½ ï½ Granular Base (63) Stress-dependent and Cross- anisotropic Model 2 3 5 6 8 9 1 4 7 ; k k k k V Hoct oct R a R a a a a a k k oct VH a a a M k P M k P P P P P G k P P P ï´ ï´ï± ï± ï´ï± ï¦ ï¶ ï¦ ï¶ ï¦ ï¶ ï¦ ï¶ ï½ ï½ï§ ï· ï§ ï· ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ ï¨ ï¸ ï¨ ï¸ ï¦ ï¶ ï¦ ï¶ ï½ ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ Granular Base (64) Moisture- sensitive, Stress- dependent, and Cross-anisotropic Model 2 3 1 1 3 ; k k V m oct R a a a H R VH V V R R I fhM k P P P M Gs r M M ï± ï´ï¦ ï¶ ï¦ ï¶ï ï½ ï§ ï· ï§ ï· ï¨ ï¸ ï¨ ï¸ ï½ ï½ Granular Base (31) Regression Models for Stress- dependent Model Coefficients ï¨ ï© ï¨ ï© 1 2 3 1.3577 0.0106 % 0.0437 0.5193 0.0073 4 0.0095 40 0.0027 200 0.003 0.0049 1.4258 0.0288 4 0.0303 40 0.0521 200 0.0251 % 0.0535 0.0672 0.0026 0.0025 0.6055 k clay wc k P P P LL wopt k P P P silt LL wopt opt wcs wopt ï§ ï§ ï½ ï« ï ï½ ï ï« ï ï ï ï½ ï ï« ï ï« ï« ï ï ï¦ ï« ï ï¶ ï§ ï· ï¨ ï¸ Subgrade Soil (65) Regression Models for Moisture-sensitive and Stress- dependent Model Coefficients ï¨ ï© ï¨ ï© ï¨ ï© ï¨ ï© ï¨ ï© ï¨ ï© ï¨ ï© 1 2 3 ln 137.19 13.60ln 4.35ln 0.62ln 36.14 0.04 3.81ln 0.22 0.77ln 4.39 0.45ln 0.01 0.05 0.15ln d A T A s T d s T k k ofc a k pfc a ï§ ï¬ ï¬ ï¬ ï¬ ï§ ï¬ ï½ï ï« ï« ï ï½ ï« ï ï ï ï½ï ï« ï ï« ï« Granular Base (31)
13 Empirical Regression Model for MR ï¨ ï©0.642555rM CBRï½ Granular Base/ Subgrade Soil (66) Empirical Regression Model for MR 1155 555rM Rï½ ï« Granular Base/ Subgrade Soil (66) Empirical Regression Model for MR 30000 0.14 i r aM ï¦ ï¶ï½ ï§ ï· ï¨ ï¸ Granular Base/ Subgrade Soil (67) Empirical Regression Model for MR ï¨ ï© 0.64 752555 1 0.728r M wPI ï¦ ï¶ ï½ ï§ ï·ï§ ï·ï«ï¨ ï¸ Granular Base/ Subgrade Soil (67) Empirical Regression Model for MR 0.64 1.12 2922555rM DCP ï¦ ï¶ï½ ï§ ï· ï¨ ï¸ Granular Base/ Subgrade Soil (66) Table 7. Permanent Deformation Models of Unbound Layers and Subgrade. Model Type Model Formulation (detailed definitions of parameters in Appendix B) Material Type Literatures Non-stress- dependent ME Model ï¨ ï©1 P r N N N ï¡ï¥ ï ï¥ ïï© ï¹ï¶ ï½ïª ïºï¶ï« ï» Granular Base/ Subgrade Soil (68) Non-stress- dependent ME Model p b r aN ï¥ ï¥ ï½ Granular Base/ Subgrade Soil (69) Non-stress- dependent ME Model 0 N p e ï¢ï² ï¥ ï¥ ï¦ ï¶ïï§ ï· ï¨ ï¸ï½ Granular Base/ Subgrade Soil (70) Non-stress- dependent ME Model ï¨ ï© ï¨ ï©, 0 kzp p zz eï¥ ï¥ ïï½ï½ Subgrade Soil (71) Stress- dependent ME Model 0 N p s v r e ï¢ï²ï¥ï¥ ï¢ ï¥ ï¥ ï¦ ï¶ïï§ ï· ï¨ ï¸ï¦ ï¶ï½ ï§ ï· ï¨ ï¸ Granular Base/ Subgrade Soil (67) Stress- dependent ME Model 6 0 1 2 6 0 1 2 log .log p oct r oct ka a a Pa Pa kb b b N Pa Pa ï¥ ï± ï´ ï¥ ï± ï´ ï© ï« ï¹ï¦ ï¶ ï¦ ï¶ï½ ï« ï«ï§ ï· ï§ ï·ïª ïºï¨ ï¸ ï¨ ï¸ï« ï» ï© ï« ï¹ï¦ ï¶ ï¦ ï¶ï« ï« ï«ï§ ï· ï§ ï·ïª ïºï¨ ï¸ ï¨ ï¸ï« ï» Granular Base (69) Stress- dependent ME Model 1 b p RCN R ï¥ ï½ ï ' f qb d c q ï¦ ï¶ ï½ ï«ï§ ï·ï§ ï· ï¨ ï¸ Granular Base (72)
14 Stress- dependent ME Model max D fB C p dAN ï´ ï¥ ï³ ï´ ï¦ ï¶ ï½ ï§ ï· ï¨ ï¸ Granular Base (11) Stress- dependent ME Model ï¨ ï© ï¨ ï©0 2 1 m nN p e J I K ï¢ï² ï¥ ï¥ ï¡ ï¦ ï¶ïï§ ï· ï¨ ï¸ï½ ï« Granular Base (73) Regression Models for Pavement ME Design Model Coefficients 60 6 4 2 3 2 6 log 0.80978 0.06626 0.003077 10 log 0.9190 0.03105 0.001806 1.5 10 log 1.78667 1.45062 3.784 10 2.074 10 1.05 10 c r r c r c c r W E W E W W E ï± ï± ï± ï± ï¥ ï³ ï¥ ï¢ ï³ ï² ï³ ï³ ï ï ï ï ï ï¦ ï¶ ï½ ï ï ï«ï§ ï· ï¨ ï¸ ï½ ï ï« ï« ï ï´ ï½ ï ï« ï ï´ ï ï´ ï ï´ Granular Base (70) Regression Models for Pavement ME Design Model Coefficients ï¨ ï© ï¨ ï© 910 0 1 9 9 0.15 20 2 log 0.61119 0.017638 4.8928510 1 10 r c e e W ï¢ ï¢ ï² ï² ï¢ ï¢ ï¥ ï¥ ï¢ ï² ï¦ ï¶ ï§ ï· ï¨ ï¸ ï¦ ï¶ ï§ ï·ï´ ï« ï´ ï§ ï· ï¨ ï¸ï½ ï½ ï ï ï¦ ï¶ ïï§ ï·ï½ ï´ ï§ ï·ï© ï¹ïï§ ï·ïª ïºï« ï»ï¨ ï¸ Granular Base (66) Regression Models for Pavement ME Design Model Coefficients 0ln 10.24 0.03 0.10 0.88 3.95 ln ln 6.74 0.02 0.04 0.85 0.03 0.13 ln 10.17 2.75 ln 0.05 2.00 1.61ln 0.34 A T G G T d G A T MBV pfc a MBV pfc a a pfc a a ï¥ ï¬ ï² ï¬ ï¢ ï§ ï¬ ï½ ï ï« ï« ï ï½ ï« ï« ï ï« ï ï½ ï ï ï ï ï Granular Base (74)
15 Table 8. Shear Strength Models of Unbound Layers and Subgrade. Model Type Model Formulation (detailed definitions of parameters in Appendix B) Material Type Literatures Non-moisture- sensitive Model tanncï´ ï³ ï¦ï½ ï« Granular Base/ Subgrade Soil (75) Moisture- sensitive Model ï¨ ï© ï¨ ï©' tan ' tan b f n a a wcï´ ï³ ï ï¦ ï¡ ï ï ï¦ï½ ï« ï ï« ï Subgrade Soil (76) Moisture- sensitive Model ï¨ ï© tantan n b a wc u uï´ ï³ ï¦ï¦ï½ ï«ï¢ï« ï Subgrade Soil (77) Moisture- sensitive Model ï¨ ï© ï¨ ï©' tan ' tan b f n a a wc Sï´ ï³ ï ï¦ ï ï ï¦ï½ ï« ï ï« ï Subgrade Soil (78) Moisture- sensitive Model ï¨ ï© ï¨ ï©' tan ' tan b f n a a wc ï«ï´ ï³ ï ï¦ ï ï ï¦ï½ ï« ï ï«ï ï Subgrade Soil (79, 80) Moisture- sensitive Model ï¨ ï© ï¨ ï© ï¨ ï© ï¨ ï© ' tan ' tanf n a a w a w a w b c ï¢ ï´ ï³ ï ï¦ ï ï ï¦ ïª ï ï ï ï ï½ ï« ï ï« ï ï© ï¹ï ï ï ïï« ï» Subgrade Soil (81) Moisture- sensitive Model ï¨ ï©' tan ' ' 1676.624 2.088 13.260 0.113 270.722ln 38.778 ' 2.827 0.016 0.0005 0.051 0.763ln 0.008 n m A A d G A S d c c MBV a fh a MBV a pfc ï´ ï³ ï¦ï± ï¬ ï§ ï¦ ï¬ ï§ ï½ ï« ï½ ï ï ï ï ï ï« ï« ï½ ï ï ï ï ï« ï Granular Base (74) Moisture- sensitive Model 2 tan 83.95 1.58 40 2.57 0.043 40 6.88 0.14 0.81 tan 1.61 0.96 0.88 4.13 31.82 n N N sN sb c c N n N PL G PI n G ï´ ï³ ï¦ ï¹ ï¹ ï¦ ï¦ ï¹ ï½ ï« ï½ ï« ï ï ï ï« ï ï½ ï ï ï ï« Granular Base/ Subgrade Soil (82)
16 Table 9. Erosion Models of Unbound Layers. Model Type Model Formulation (detailed definitions of parameters in Appendix B) Material Type Literatures Empirical Model ESALg ï¢ ï² ï¦ ï¶ ï½ï§ ï· ï¨ ï¸ Granular Base (83) Empirical Model log 1.07 0.34 i dP m ESAL f m D ï½ ï ï ï½ ï ï¥ Granular Base (84) Empirical Model exp 2.884 1.652 log 10,000 ESAL DE NPI ï© ï¹ï¦ ï¶ï ï½ ï ï« ïïª ïºï§ ï· ïª ïºï¨ ï¸ï« ï» ï¥ Granular Base (85) Empirical Model 36.67 2.884 1.652 log 10, 000 P N PI E SAL D E N PI F ï½ ï ï© ï¹ï¦ ï¶ï ï½ ï ï ï« ïïª ïºï§ ï· ïª ïºï¨ ï¸ï« ï» ï¥ Granular Base (86) Empirical Model ï¨ ï©0.1031 2 1 log 14.524 6.777 9.0 100 m i i i N C P C nPercent erosion damage Nï½ ï½ ï ï ï½ ï¥ Granular Base (87) Empirical Model Table-based Erodibility Class Assessment Granular Base (66) ME Model ï¨ ï© ï¨ ï©0% D N vf Erosion f e ï¢ ï²ï¦ ï¶ ïï§ ï·ï§ ï·ïï¨ ï¸ï½ Granular Base/ Subgrade Soil (24) Table 10. Foundation Models of Subgrade. Model Type Model Formulation (detailed definitions of parameters in Appendix B) Material Type Literatures No-shear Model (x,y) kw(x,y)p ï½ Granular Subbase/ Subgrade Soil (88) No-shear Model 2(x,y) kw(x,y) (x,y)p T wï½ ï ï Granular Subbase/ Subgrade Soil (89) No-shear Model 2 2(x,y) kw(x,y) (x,y)p D wï½ ï ïï Granular Subbase/ Subgrade Soil (90) Shear-included Model 2(x,y) kw(x,y) G (x,y)p wï½ ï ï Granular Subbase/ Subgrade Soil (91) Shear-included Model 2 2(1 )p kw Gk G p w c c ï« ï ï ï½ ï ï Granular Subbase/ Subgrade Soil (92)
17 Table 11. Thickness Sensitive Models of Unbound Layers. Model Category Model Type Model Formulation Literatures Modulus Models Nonlinear Stress-dependent Models in Table 6 See Table 6 See Table 6 Moisture-sensitive and Stress-dependent Models in Table 6 Stress-dependent and Cross-anisotropic Models in Table 6 Moisture-sensitive, Stress-dependent, and Cross- anisotropic Model in Table 6 Permanent Deformation Models Stress-dependent ME Models in Table 7 See Table 7 See Table 7 Regression Models for Pavement ME Design Model Coefficients in Table 7 Shear Strength Models Moisture-sensitive Models in Table 8 See Table 8 See Table 8 Erosion Models ME Models in Table 9 See Table 9 See Table 9