BS ISO 16134-2020 Earthquake-resistant and subsidence- resistant design of ductile iron pipelines.
4 Earthquake-resistant design
4.1 Seismic hazards to buried pipelines
In general, there are several main causes of seismic hazards to buried pipelines:
a) ground displacement and ground strain caused by seismic ground shaking;
b) ground deformation such as a ground surface crack, ground subsidence and lateral spread induced by liquefaction;
c) relative displacement at the connecting part with the structure, etc.;
d) ground displacement and rupture along a fault zone.
Since the ductile iron pipe has high tensile strength as well as the capacity for expansion/contraction and deflection from its joint part, giving it the ability to follow the ground movement during the earthquake, the stress generated on the pipe body is relatively small. Few ruptures of pipe body have occurred during earthquakes in the past. It is therefore important to consider whether the pipeline can follow the ground displacement and ground strain without slipping out of joint when considering its earthquake resistance. The internal hydrodynamic surge pressures induced by seismic shaking are normally small enough not to be considered.
4.2 Qualitative design considerations
To increase the resistance of ductile iron pipelines to seismic hazards, the following qualitative design measures should be taken into consideration.
a) Provide pipelines with expansion/contraction and deflection capability.
EXAMPLE Use of shorter pipe segments, special joints or sleeves and anti-slip-out mechanisms according to the anticipated intensity or nature of the earthquake.
b) Lay pipelines in a firm foundation.
c) Use smooth back fill materials.
NOTE Polyethylene sleeves and special coating are also effective in special cases.
d) Install more valves.
4.2.2 Where high earthquake resistance is needed
It is desirable to enhance the earthquake resistance of parts connecting the pipelines to structures and when burying the pipes in
a) soft ground such as alluvium,
b) reclaimed ground,
c) filled ground,
d) suddenly changing soil types (geology) or topography,
e) sloping ground,
1) near revetments,BS ISO 16134 pdf download.