Seismic risk management for water pipeline networks - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 628

t G

t cr

g

0

23.6 Shear stress and strain acting between the pipe surface and the
surrounding ground.

Ground surface B A

Free field displacement

Contact surface between pipe and surrounding soil

Elongated
joint
portion

Pipeline

D joint

23.7 Pipe elongation induced by the surrounding soil.

stress τ G is greater than the critical shear stress,

on the other hand, the maximum pull-out force can be computed from the
following critical shear stress:

τ G . When the shear stress

π Dl

Dl

⋅ ⋅ τ for

for

τ < τ

⎩

eff G G cr

[23.12]

S =

π ⋅ ⋅ τ τ ≥ τ

eff cr G cr

where l eff is the effective length loaded by the shear stress acting on the pipe
surface.
When a seismic excitation is applied to the ground surface and pipeline
as shown in Fig. 23.7, the ground is deformed. Note that the deformation
profi le in the ground is not uniform in the vicinity of the pipeline because
of the difference between the pipe stiffness and the soil stiffness. The pipe
elongation is forced by the shear stress acting on the pipe surface which is
transmitted by the shear deformation of the surrounding soil.