28 February 2006
Figure 2-4 Example Chapter Replacement
10 May 2000
15 June 2000
CHAPTER 2 FROST PROTECTION DESIGN
NEED FOR FROST PROTECTION. Differential frost heaving can cause
pavement cracking, significant roughness, and a drastic reduction in pavement service
life. If prevented from free movement, frost heaving can exert enormous forces on
pavements, structures, or utilities. The forces involved are so great that any attempt to
accommodate frost heaving by providing a more substantial pavement structure is not
practical. The only practical solution is prevention. Even if frost action does not result
in significant heaving, the excess free water during thaw periods, and consequent
softening of the subgrade and base material, can also be detrimental to pavement
performance. If the investigation for frost design (refer to Section 2) reveals that frost
action is possible at the project site, frost protection design must be considered. In
general, the following combination of conditions denotes a potential for frost action and
the need for frost protection:
Presence of frost-susceptible soil.
Groundwater level within 5 ft (1.5 m) of the proposed subgrade elevation.
Frost penetration depth greater than the planned overall thickness of the
pavement structure (typically, design freezing index greater than 150
degrees F (83.3 degrees C)).
DESIGN APPROACH. There are two basic approaches to frost protection:
(a) complete prevention of subgrade freezing and (b) limiting frost penetration into the
subgrade. The first method involves providing a sufficient cover over the frost-
susceptible material to prevent penetration of freezing temperatures into the subgrade.
This may require removing and replacing a certain thickness of frost-susceptible
material or providing a layer of non-susceptible fill, if the combined thickness of the
pavement structure and any fills needed for geometric requirements are not sufficient
to provide adequate cover. The second approach allows limited frost penetration into
the subgrade. The applicability and details of each of these design approaches are
discussed in the following.