Environmental Factors of Mepdg Pavement Design Guide

833 Words4 Pages
Environmental Effects on the Resilient Modulus Temperature and moisture are the two most influential factors that can significantly affect the pavement and subgrade properties. Because of this, they also have a large influence on its carrying capacity. This paper will only focus on the unbound materials such as the subgrade. This is because the subgrade has the greatest affect on the carrying capacity of pavement. The unbound materials are most affected by moisture unless the temperature drops below 32° F and ice is formed. In this case, the subgrade resilient modulus (MR) value can increase as much as 120 times higher than its original value. When the subgrade begins to undergo the effects of thawing, it will become saturated which greatly reduces the resilient modulus value. Hence, as moisture content increases within unbound materials, the resilient modulus value decreases. For this reason, it is possible to develop a model that analytically predicts changes in modulus do to moisture change. The design guide is able to evaluate the effects of temperature change and moisture in the pavement structure and subgrade over the design life of a pavement through a modeling tool called the Enhanced Integrated Climate Model (EICM). The EICM is a one-dimensional coupled heat and moisture flow program that simulates the characteristics and behavior of pavement and sub-grade materials in conjunction with the environment over years of operations. The stress state, variations in moisture, and freeze/thaw effects are all used to evaluate the resilient modulus within the design guide. For the design guide approach, there are three levels at which MR can be estimated: Level 1: Only the stress sensitivity of the unbound layers is accounted for. Level 2: An estimate of MR is used at a reference moisture condition which is determined near optimum moisture content and maximum
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