Seismic risk assessment for oil and gas pipelines - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 701

Nonliquefiable subsurface deposit
Trench fill
Nonliquefiable surface deposit
Liquefiable soil deposit

Q4

Q3

Q5

At ground surface

A

At pipeline elevation

Q2

B

Lateral spread length

θ

Q1

Q6

Q3

River crossing
section A-A A

B

Q7

Sources of uncertainty
Q1: Subsurface soil characteristics
Q2: Direction of displacement
Q3: Width and length of spread zone
Q4: Distribution of displacement within spread
Q5: Location of spread along river bank
Q6: Simultaneous displacement on opposite river banks
Q7: Influence of backfill on pipe-soil interaction

Section B-B

25.5 Uncertainties associated with quantifying lateral spread
displacement hazards.

there will not be suffi cient information on the severity or prevalence of girth
weld defects that could reduce pipeline tension strain capacity. This diffi -
culty is normally addressed by simply assuming a tension strain capacity
based upon assumed fl aw severity. Another alternative, if portions of the
pipeline are removed to provide some pipe weld information, is to assume
the removed pipe is identical to the remaining pipe and assign a strain
capacity based upon a fi tness for purpose assessment. API 1101 Appendix
A (API, 2010) and API 579 (API, 2007) provide methodologies for defi ning
girth weld strain capacity, but these methods can be extremely conservative
and require special knowledge and experience to implement correctly.

25.10.4 Acceptable risk

As risk is defi ned as the product of vulnerability and consequences, a 0.01%
(1 in 10 000) chance per year of an event causing 1000 deaths is equivalent
to a 10% chance per year of an event causing the death of one person.
Therefore, risk alone is generally insuffi cient for making decisions where
the general public is involved because it is extremely diffi cult to educate
the public to accept serious consequences, such as death. Conversely, the