Civil Engineering Reference
In-Depth Information
CHAPTER 15
SUMMARY OF
GEOTECHNICAL
EARTHQUAKE ENGINEERING
15.1 INTRODUCTION
The purpose of this final chapter is to present a summary of geotechnical earthquake engineer-
ing. The type of project will govern the required site investigation and engineering analyses.
For example, an essential facility will require a more extensive investigation than a temporary
structure. The governing building codes or local ordinances may also have regulations that
require specific investigations and analyses that are different from those outlined in this
chapter. The geotechnical engineer and engineering geologist should always check with the
governing authority prior to the start of a geotechnical earthquake engineering investigation.
In summary, most damage caused by significant earthquake shaking is related to one or
a combination of the following three factors:
1.
Geologic hazards:
These include surface fault rupture, regional subsidence, and
tsunami (Chap. 3). Structures are simply unable to resist the destructive forces generated
by fault rupture, regional subsidence, and tsunami.
2.
Structural defects:
Collapse of structures often occurs because they are unrein-
forced, poorly constructed, overloaded, or weakened from age or rot. Other common causes
of collapse are related to poor design, such as a soft story, torsional problems, inadequate
shear walls, pounding damage from adjacent structures, and resonance of the structure
(Chap. 4).
3.
Weakening of the soil:
Most soil related failures are due to the weakening of the
soil during the earthquake. This includes the liquefaction of loose sand and the cyclic
softening of soft cohesive soil. In geotechnical earthquake engineering, the most impor-
tant item that the geotechnical engineer needs to determine is whether the earthquake will
weaken the soil at the site.
15.2
SUMMARY OF SITE INVESTIGATION
Because of the importance of geology in geotechnical earthquake engineering, an
engineering geologist should be involved in the site investigation. Concerning the
importance of geology, Rollings and Rollings (2005) describe eight case studies where
15.1
