OTHER GEOTECHNICAL EARTHQUAKE ENGINEERING ANALYSES - Geotechnical Earthquake Engineering - page 351

FIGURE 11.3 Close-up view of the fault plane. The striations indicate predominantly horizontal movement
with some vertical movement. ( Photograph from the Steinbrugge Collection, EERC, University of California,
Berkeley. )
11.3 PAVEMENT DESIGN
11.3.1 Introduction
In terms of pavement design, one of the main objectives is to provide an adequate pavement
thickness in order to prevent a bearing capacity failure. For example, unpaved roads and roads
with a weak subgrade can be susceptible to bearing capacity failures caused by heavy wheel
loads. The heavy wheel loads can cause a general bearing capacity failure or a punching-type
shear failure. These bearing capacity failures are commonly known as rutting, and they develop
when the unpaved road or weak pavement section is unable to support the heavy wheel load.
Because the thickness of the pavement design is governed by the shear strength of the
soil supporting the road, usually the geotechnical engineer tests the soil and determines the
pavement design thickness. The transportation engineer often provides design data to the
geotechnical engineer, such as the estimated traffic loading, required width of pavement,
and design life of the pavement.
Pavements are usually classified as either rigid or flexible depending on how the surface
loads are distributed. A rigid pavement consists of Portland cement concrete slabs, which
tend to distribute the loads over a fairly wide area. Flexible pavements are discussed in the
next section.
11.3.2 Flexible Pavements
A flexible pavement is defined as a pavement having a sufficiently low bending resistance,
yet having the required stability to support the traffic loads, e.g., macadam, crushed stone,
gravel, and asphalt (California Division of Highways 1973).