Earthqua ke-resistant and subsidence
BS ISO 16134:2020 pdf free.Earthqua ke-resistant and subsidence- resistant design of ductile iron pipelines.
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 2531, Ductile iron pipes,fittings, accessories and their joints for water applications
3 Terms and definitions
For the purposes of this document, the terms and delinit ions given in ISO 2531 and the following apply.
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3.1 burying placing of pipes underground in a condition where they touch the soil directly
3.2 response displacement method earthquake-resistant calculation method in which the underground pipeline structure is affected by the ground displacement in its axial direction during an earthquake
3.3 liquefaction phenomcnon in which sandy ground rapidly loses its strength and rigidity due to repeated stress during an earthquake, and where the whole ground behaves just like a liquid
3.4 earthquake-resistant Joint joint having slip out resistance as well as expansion/contraction and deflection capabilities
3.5 flexible joint joint having expansion and deflection capabilities4.1 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
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) flld ground,
d) suddenly changing soil types (geology) or topography,
e) sloping ground,
f) near revetments,
g) liquefiable ground, and/or
4.3 Design procedure
To make earthquake-resistant design for ductile iron pipelines:
a) select the piping route;
b) investigate the potential for earthquakes and ground movement;
c) assume probable earthquake motion (seismic intensity);
d) undertake earthquake resistance calculation and safety checking;
e) select joints.
Solid/firm foundations should be chosen for the pipeline route.
When investigating earthquakes and ground conditions, take into account any previous earthquakes in the area where the pipeline is to be laid.
4.4 Earthquake resistance calculations and safety checking
When checking the resistance of pipelines to the effects of earthquakes, the calculation shall be carried out for the condition in which the normal load (dead load and normal live load) is combined with the influence of the earthquake.
The pipe body stress, expansion/contraction value of joint, and deflection angle of joint are calculated by the response displacement method. Earthquake resistance is checked by comparing these values with their respective allowable values. The basic criteria are given in Table 1.
A flowchart of earthquake resistance determination and safety checking is shown in Figure 1. The basic formulae only for earthquake resistance calculation are given in 4.S. A detailed example of calculation is given in Annex A.
4.5 Calculation of earthquake resistance一Response displacement method
This method shall be used except when the manufacturer and the customer agree on an alternative recognized method.
4.5.2 Design earthquake motion
The design acceleration for different seismic intensity scales can be determined according to the relationship between the several kinds of seismic intensity scales and the acceleration of ground surface, as given in Annex B.
Large scale ground deformation such as ground cracks, ground subsidence and lateral displacement near revetments and inclined ground can be generated by liquefaction during an earthquake. Since such ground deformations can affect the buried pipeline, it is necessary to consider this possibility and to take it into account in the pipeline design.
5.2 Evaluation of possibility of liquefaction
The possibility of liquefaction shall be evaluated for soil layers when the following conditions are present:
a) saturated soil layer 25 m from the ground surface;
b) average grain diameter. D59. 1O mm;
c) content by weight of small grain particles (with grain diameter O,075 mm) 30 %.
6.2 Basic safety checking
For ground subsidence in soft ground such as reclaimed ground, safety shall be checked by observing if the pipeline can absorb the ground movement by expansion/contraction and deflection of the joints.This way of safety checking is the same as for the ground deformation in the pipe perpendicular direction induced by liquefaction, which is given in Annex D.
7 Pipeline system design
7.1 Pipeline components
According to the results of calculations for expansion/contraction, slip-out resistance, and joint deflection, the pipeline system may be designed using the same joint for all pipes, or, alternatively,using a range/combination of pipeline components. If necessary, pipeline system components may be classified according to Table 3.
7.2 Countermeasures for large ground deformation such as liquefaction
In cases where pipelines are to be laid in locations where ground deformation could be induced by liquefaction during an earthquake, and where ground subsidence is anticipated in soft soil such as reclaimed ground, a pipeline having earthquake-resistant joints with slip-out resistance, as well as an expansion/contraction and deflection capability, should be used.BS ISO 16134 pdf free download.Earthqua ke-resistant and subsidence