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Suggested Citation:"Appendix F. Sensitivity Analysis of Modulus of Subgrade Reaction Model." National Academies of Sciences, Engineering, and Medicine. 2019. Proposed Enhancements to Pavement ME Design: Improved Consideration of the Influence of Subgrade and Unbound Layers on Pavement Performance. Washington, DC: The National Academies Press. doi: 10.17226/25583.
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Suggested Citation:"Appendix F. Sensitivity Analysis of Modulus of Subgrade Reaction Model." National Academies of Sciences, Engineering, and Medicine. 2019. Proposed Enhancements to Pavement ME Design: Improved Consideration of the Influence of Subgrade and Unbound Layers on Pavement Performance. Washington, DC: The National Academies Press. doi: 10.17226/25583.
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Suggested Citation:"Appendix F. Sensitivity Analysis of Modulus of Subgrade Reaction Model." National Academies of Sciences, Engineering, and Medicine. 2019. Proposed Enhancements to Pavement ME Design: Improved Consideration of the Influence of Subgrade and Unbound Layers on Pavement Performance. Washington, DC: The National Academies Press. doi: 10.17226/25583.
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F-1 Appendix F. Sensitivity Analysis of Modulus of Subgrade Reaction Model Sensitivity analysis was performed on the Artificial Neuron Network (ANN) model for modulus of subgrade reaction (modified k-value) to evaluate the effect of various input variables on the relationship between slab-base degree of bonding and modified k-value. The input variables include the thickness of slab and base course, modulus of slab, base course, and subgrade. Table F.1 lists the change of various input values for sensitivity analysis. Figure F.1 presents the effect of various input variables on the relationship between degree of bonding and modified k-value. Generally, the modified k-value increases with the greater the degree of bonding. The thicker PCC slab or base course can help improve the value of modulus of subgrade reaction. Likewise, the larger modulus of base layer or subgrade is the higher modified k-value is. Additionally, the higher modulus of PCC slab enhances the modified k-value but after a threshold, the modified k-value reverses the order. Table F.1. Change of Various Input Values for Sensitivity Analysis. Input Variable Change of Input Values Slab thickness, in 4, 8, 12 Base thickness, in 2, 6, 10 Slab modulus, psi 1450380, 2900760, 5801520, 8702280 Base modulus, psi 4351, 23206, 46412, 62366, 92824 Subgrade modulus, psi 5076, 20305, 40610 Degree of bonding 0, 0.3, 0.6, 1 (a) Effect of slab thickness

F-2 (b) Effect of base thickness (c) Effect of slab modulus

F-3 (d) Effect of base modulus (e) Effect of subgrade modulus Figure F.1. Effect of Various Input Variables on Relationship between Degree of Bonding and Modified k-value.

Next: Appendix G. Determination of Stress State in the Faulting Model »
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The performance of flexible and rigid pavements is known to be closely related to properties of the base, subbase, and/or subgrade. However, some recent research studies indicate that the performance predicted by this methodology shows a low sensitivity to the properties of underlying layers and does not always reflect the extent of the anticipated effect, so the procedures contained in the American Association of State Highway and Transportation Officials’ (AASHTO’s) design guidance need to be evaluated.

NCHRP Web-Only Document 264: Proposed Enhancements to Pavement ME Design: Improved Consideration of the Influence of Subgrade and Unbound Layers on Pavement Performance proposes and develops enhancements to AASHTO's Pavement ME Design procedures for both flexible and rigid pavements, which will better reflect the influence of subgrade and unbound layers (properties and thicknesses) on the pavement performance.

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