Civil Engineering Reference
In-Depth Information
engineer. This final chapter of Part 2 describes some of these analyses, such as surface
fault rupture and groundwater (Sec. 11.2), pavement and pipeline design (Secs. 11.3-
11.4), response spectrum (Sec. 11.5), and foundations on rock and deep foundations (Secs.
11.6 -11.7).
11.2
SURFACE RUPTURE ZONE
11.2.1 Introduction
Section 3.2 presents an introduction into surface rupture. Examples of damage caused by
surface rupture are shown in Figs. 3.3 to 3.13.
The best individual to determine the location and width of the surface rupture zone is the
engineering geologist. Seismic study maps, such as the
State of California Special Studies
Zones Maps
(1982), which were developed as part of the Alquist-Priolo Special Studies Zones
Act, delineate the approximate location of active fault zones that require special geologic
studies. These maps also indicate the approximate locations of historic fault offsets, which are
indicated by year of earthquake-associated event, as well as the locations of ongoing surface
rupture due to fault creep. There are many other geologic references, such as the cross section
shown in Fig. 5.2, that can be used to identify active fault zones. Trenches, such as shown in
Fig. 5.8, can be excavated across the fault zone to more accurately identify the width of the
surface rupture zone.
11.2.2 Design Approach
Since most structures will be unable to resist the shear movement associated with surface
rupture, one design approach is to simply restrict construction in the fault shear zone. Often
the local building code will restrict the construction in fault zones. For example, the
Southern Nevada Building Code Amendments
(1997) state the following:
Minimum Distances to Ground Faulting:
1.
No portion of the foundation system of any habitable space shall be located less than five
feet to a fault.
2.
When the geotechnical report establishes that neither a fault nor a fault zone exists on the
project, no fault zone set back requirements shall be imposed.
3.
If through exploration, the fault location is defined, the fault and/or the no-build zone shall
be clearly shown to scale on grading and plot plan(s).
4.
When the fault location is not fully defined by explorations but a no build zone of potential
fault impact is established by the geotechnical report, no portion of the foundation system
of any habitable space shall be constructed to allow any portion of the foundation system to
be located within that zone. The no build zone shall be clearly shown to scale on grading
and plot plan(s).
5.
For single lot, single family residences, the fault location may be approximated by histori-
cal research as indicated in the geotechnical report. A no build zone of at least 50 feet each
side of the historically approximated fault edge shall be established. The no build zone shall
be clearly shown to scale on grading and plot plan(s).
In many cases, structures will have to be constructed in the surface rupture zone. For
example, transportation routes may need to cross the active shear fault zones. One approach
is to construct the roads such that they cross the fault in a perpendicular direction. In addition,
