Lesson 3/Learning Event 3
Design of Pavement for Frost Action
The design of pavements in frost areas can be based on either of two basic concepts: control of surface
deformation resulting from frost action, or provision of adequate bearing capacity during the most
critical climatic period. Under the first concept, sufficient combined thickness of pavement and
nonfrost-susceptible base must be provided to eliminate or limit to an acceptable amount, subgrade frost
penetration and effect thereof. Under the second concept, the amount of heave which will result is
neglected and design is based solely on the anticipated reduced strength of the subgrade during the frost-
melting period. The following three design methods have been derived from these concepts:
Complete Protection Method
Limited Subgrade Frost Penetration Method
Reduced Subgrade Strength Method
The first step in determination of design thickness is to select the appropriate design method or methods
from Table 13, which summarizes the conditions for which each of the above methods is applicable.
The degree of horizontal variability of subgrade soil and moisture conditions may be classified into one
of four categories: Uniform, slightly variable, variable, or extremely variable. Definitions of these
adjective categories are given under the respective adjective headings in Table 13. The distinctions are
purely qualitative. Selection of the adjective category involves the exercise of judgment; it must be
based on careful analysis of past performance of pavement in the area and very thorough study of the
data revealed by the site explorations. An airfield may fall entirely into one adjective category, or it may
have to be divided into a number of areas for separate design consideration. Once an adjective category
has been chosen, the design approaches which are applicable may be ascertained from Table 13.
It should be noted that the requirement for sufficient bearing capacity during the normal period (summer
and fall), as determined by temperate design, takes precedence over the frost design criteria if it requires
greater combined thickness than that obtained by the frost design methods.
Thicknesses of pavement surfacing and high quality base are not changed during the frost design.
Thickness adjustments required to attain the combined thicknesses determined for frost design of the
controlling pavement types will be made in the lower base materials provided for frost design.