Geology Reference
In-Depth Information
There are four major considerations for design:
1. Local ground failure, e.g. because of liquefaction in loose saturated
cohesionless sand and silt.
2. Rupture because of fault movement, which can be signi
cant
especially for tunnel design.
3. Ground shaking causing inertial forces. Buildings and slopes are
especially at risk from horizontal shaking.
4. Remote hazards. These will include landslides from adjacent land
where debris run-out could impact the site, and tsunamis.
Most structures need to be designed to withstand dynamic loading.
This includes wind loading (to typhoon levels in countries such as
Japan, Korea and Hong Kong), earthquakes and blasting/traf
c. The
main one of these that requires input from the engineering geologist is
earthquake loading. The level of hazard is assessed at the site investi-
gation stage (
Chapter 4),
and there is often a mandatory design code
for a particular country. Alternatively, or as a check, the design team
will identify some design earthquake or series of such design events
with equal probability of occurrence within the lifetime of the struc-
ture. For example, statistical analysis of historical earthquake activity
might indicate that there is an equal chance of a magnitude 8 (M8)
earthquake at 200 km distance, as a magnitude 5.2 (M5.2) earthquake
at 10 km. These earthquakes would probably result in very different
ground shaking at the project site. From study of recorded data using
Figure 6.30
Peak
acceleration vs.
distance for
earthquakes
(European data).
Equations given in
Ambraseys
et al
.
(1996).
0.35
0.3
0.25
MS = 4
MS = 5
0.2
MS = 6
MS = 7
0.15
0.1
0.05
0
5
50
Kilometres from epicentre
500
