Geoscience Reference
In-Depth Information
natural gas. The sources of PGD involve landslides, soil liquefaction, and surface fault-
ing. The generic patterns of displacement for earthquake-triggered ground failure are
similartothoseforlandslides,subsidence, andground deformationassociatedwithdeep
excavation, tunneling, and mining activities.
The systematic analysis of pipeline repair records after the 1994 Northridge earthquake
show the locations of important seismic and geotechnical hazards and are used to iden-
tify zones of potential ground failure not recognized in previous explorations and risk
assessments. Moreover, the systematic assessment of pipeline repairs with GIS result
in regressions that link damage rates to various levels of strong motion. Such relation-
shipsareimportantforlossestimationstudiesoffutureearthquakeeffectstoplanforand
reduce the potential for seismicdisruption.
Large-scale tests of pipeline response to abrupt ground rupture have resulted in analyti-
cal models that can simulate such behavior at critical locations, such as pipeline elbows,
where local soil restraint and the 3-D distribution of deformation leads to increased risk
of failure. Large-scale tests of soil-pipeline interaction show that soil-structure interac-
tion for partially saturated sand results in significantly greater concentration of pipeline
strain than for dry sand. Full-scale tests of soil-structure interaction for buried pipelines
subjected to large horizontal movements under 2-D conditions indicate that maximum
lateral forces are approximately twice as high for large horizontal displacement in par-
tially saturated sand as for dry sand. These conditions apply to pipeline locations near
the center of a lateral spread or landslide. Design charts are developed on the basis of
experimental results to predict maximum lateral load for different depths of burial, pipe
diameters, and soil angle of shear resistance associated with partially saturated and dry
sand.
Large-scaletestsonHDPEpipelinesshowthatsuchpipinghastheflexibilityandductility
to withstand substantial amounts of abrupt ground deformation. Because of its visco-
elastic characteristics, the axial load in HDPE relaxes after ground failure, thus having
the beneficial effect of reducing loads on anchorages either side of the concentrated soil
deformation.
A complex 3-D soil deformation and rupture pattern is observed either side of the strike
slip rupture plane in large-scale tests. The progressive, 3-D characteristics of soil fail-
ure near the main ground rupture plane results in a p-y relationship significantly differ-
ent than that for 2-D conditions in partially saturated sand. The large-scale tests show
that 3-D conditions near the abrupt ground rupture result in peak lateral force per unit
pipeline length that are approximately 40%-50% of the peak lateral force for pipe with
similar geometry, depth, and soil under 2-D conditions of relative soil-pipe horizontal
displacement.
Acknowledgments
Thanks are extended to the National Science Foundation, Multidisciplinary Center for
Earthquake Engineering Research, Los Angeles Department of Water and Power, NEES
