3550-8310-sp-0006 rev d2.pdf marked-c.van

8/13/2019 3550-8310-SP-0006 Rev D2.pdf MARKED-c.van

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SPECIFICATIONS FOR

THE FOUNDATIONS

OF STORAGE TANKS

FOSTER WHEELER ENERGY LTD

PROJECT SPECIFICATION

CIVIL

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1. SCOPE

This Specification, together with drawing 3550-8310-39-0015 represents thepractice to be followed for the design of foundations for vertical atmospheric storagetanks.

2. REFERENCES

2.1 General

Design shall conform to the latest revision of the following Specifications, Standardsand Codes of Practice current at the time of contract award.

It shall be executed and completed with full compliance to all National and locallaws and bye laws and regulations.

The order of precedence shall be as follows and design shall be based on the moststringent of them:

1) Mandatory Vietnamese Standards

2) Project Specifications3) International or Vietnamese Applicable Codes

In the event of a conflict between specifications and/or standards and/or national orlocal laws or bye laws, the Employers decision shall be sought and govern.

The CONTRACTOR shall obtain all of the Employersspecification and standards.

2.2 Specifications, Codes & Standards

The Work shall be performed to the following specifications and standards or itsequivalent.

2.2.1 Project Specifications

3550-8820-SP-0001 - Basic Engineering Design Data (BEDD)

3550-8310-SP-0001 - Design Loadings

3550-8310-SP-0005 - Specification for Concrete Works

3550-8310-SP-0008 - Design of Concrete Foundations, Structures,Asphalt Roads & Paving

3550-8310-SP-0009 - Earthwork Specification

2.2.2 Soil Investigation Report

28030/4 - Geotechnical Report from Soil Mechanics


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2.2.3 Project Civil Standard Drawings

3550-8310-39-0015 - Typical Foundation Detail for Vertical AtmosphericStorage Tanks

2.2.4 Vietnamese National Standards

Vietnamese Building Code, Vol I General Provisions & Construction Planning

Vietnamese Building Code, Vol II -

Vietnamese Building Code, Vol III -

TCXDVN 375:2006 Design of Structures for EarthquakeResistance

2.2.5 British Standards

BS 1377 Soils for civil engineering purposes.

: Part 4 Compaction related tests

BS 6031 Code of Practice for Earthworks

BS 7361 Cathodic Protection

: Part 1 Code of Practice for Land and Marine Applications

BS 8004 Code of Practice for Foundations

BS 8110 Structural Use of Concrete

: Part 1 Code of Practice for Design & Construction

: Part 2 Code of Practice for Special Circumstances

: Part 3 Design Charts for Singly Reinforced Beams, DoublyReinforced Beams and Rectangular Columns

2.2.6 Eurocodes

Design to Eurocodes shall be in conjunction with the corresponding British NationalAnnex

BS EN 1992 Eurocode 2: Design of concrete structures

: Part 1-1 General rules and rules for buildings

: Part 1-2 General rules. Structural fire design

BS EN 1997 Eurocode 7: Geotechnical Design

: Part 1 General rules


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SPECIFICATIONS FOR

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CIVIL

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: Part 2 Ground investigation and testing

3. GENERAL

The design of tank foundations shall be based on the recommendations and designparameters given in the Geotechnical Investigation Report.

All anticipated settlement and deformations of the foundation shall be reported tothe Tank Engineer and the Piping Engineer in order for them to assess if theanticipated movement of the tank is acceptable for the design of the tank and the

tank piping attachments. The Contractor shall report the expected immediate,elastic and long term consolidation settlements for individual tank foundations forEmployers approval.

The type of foundation to be used shall be as follows:

Tanks with diameter:

> 25m TYPE 1 to standard drawing 3550-8310-39-0015

> 10m & < 25m TYPE 2 to standard drawing 3550-8310-39-0015

< 10m TYPE 3 to standard drawing 3550-8310-39-0015

4. SUBGRADE

4.1 The subgrade shall be capable of supporting the tank, its attachments andits maximum weight of contents without general and/or local shear failure orexcessive:

a) Unequal settlementb) Centre to edge settlementc) Total settlementd) Deformation in tank floor slope

4.2 Where the subgrade is capable of supporting the tank and its contents, thesoil shall be thoroughly compacted in accordance with BS 6031 orequivalent applicable standard. Soft spots shall be removed and replacedwith compacted fill of granular or other stable material compacted to thesame density as the subgrade.

4.3 If the subgrade is unable to support the loadings from the tank withoutexcessive unequal or total settlement, the Contractor shall submit forEmployers approval consideration of using one or a combination of thefollowing methods to improve the subgrade:

a) Remove the unsuitable subgrade and replace with thoroughly compactedgranular fill material or other stable material.

b) Deep compaction of the unsuitable subgrade by vibro flotation or dynamicconsolidation.


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c) Consolidation of the unsuitable subgrade by temporary preloading with orwithout providing vertical drains drilled into the subgrade to accelerate therate of consolidation.

d) Piling

e) Rigid raft type foundation

f) Ground stabilization

5. TANK ELEVATION

The height above grade of the tank floor after total settlement shall not be less than300mm unless otherwise approved by the Employer. Where tank foundationsrequire leak detection to be provided to protect the environment and prevent groundcontamination, it may be necessary to increase the height of the tank to more than300 mm above grade.

6. RING BERM FOUNDATION

6.1 Ring berms

Ring berms shall:-

Be constructed with well graded granular material or crushed stone asapproved by the Employer, thoroughly compacted to 95% compaction, inaccordance with BS 6031 or equivalent applicable standard, within thegrading limits shown in Table 1.

SIEVE SIZE

(mm)

PERCENTAGE PASSING

(BY WEIGHT)

50 100

10 85 - 1005 70 - 90

1 30 - 70

0.5 20 - 50

0.1 10 - 20

0.05 10

TABLE 1

Be compacted in layers not exceeding 200mm thickness whenuncompacted.

Have a 2.5m minimum width at the top with sloping sides of 1 vertical to 1.5horizontal.

Have compaction trials carried out on compacted fill in accordance with BS1377: Part 4 or equivalent applicable standard.


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6.2 Granular Fill PadsGranular fill pads shall:-

be constructed of inert granular or other stable material approved by the

Employer.

be spread in layers of uncompacted thickness not greater than 200mm andshall have a moisture content sufficiently close to optimum such that it canachieve compaction corresponding to 95% of the dry density obtained in testaccording to BS 1377 or equivalent applicable standard.

Have compaction trials carried out on compacted fill in accordance with BS1377: Part 4 or equivalent applicable standard.

6.3 Crushed Stone Layer

The top of the granular fill pads shall be covered by crushed stone layer. Thisconsist of100mm thickness of compacted crushed stone or gravel, well gradedfrom 10mm to 20mm. Chips and quarry dust shall be used to fill in the surfacevoids.

6.4 Oil-Sand Layer

The top of the crushed stone layer shall be covered by Oil - sand layer. This consistof 50mm thick layer of mixture of washed and dried salt free sand well mixed withapproximately 75l/m3 lube oil without additives. Precaution shall be taken not to useused oil due to danger of corrosion.

Trial mixes shall be produced in order to obtain an acceptable compositionapproved by the Employer.

7. CONCRETE RING BEAMS

Concrete ring beams shall be designed and constructed in accordance with BS8004 and BS 8110 or equivalent applicable standard.

Concrete ring beams shall be designed to resist the following simultaneousconditions:

a) to span 4.0m horizontally unsupported.b) to resist the surcharge from the tank.c) to resist pressure from the retained earth.

Concrete ring beams shall be of adequate width to ensure that thetheoretical unit bearing pressure at the bottom of the ring beam is the same

as the theoretical unit bearing pressure at the centre of the filled tank.

Concrete ring beams shall be of adequate width and depth to accommodatetank holding down bolts.


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Concrete ring beams shall be designed to control cracking appropriate to theprevailing exposure conditions.

8. REINFORCED CONCRETE RAFT FOUNDATIONS

Reinforced concrete raft foundations shall be designed and constructed inaccordance with TCVN 4453 or BS 8004 whichever is more onerous.

9. PILED FOUNDATIONS

Piled foundations shall be designed and constructed in accordance with TCVN 4453

or BS 8004 whichever is more onerous. The concrete pad shall be designed to spanbetween the piles assuming no pile failure and investigated for the case assumingdifferential settlement of individual piles. Geotechnical engineering advice shall betaken in assessing the amount of differential settlements of piles.

10. PERMISSIBLE FOUNDATION SETTLEMENT

10.1.1 Total Settlement

Total post-construction settlement for individual tank foundations shall not exceed

the values noted in the table in 10.1.2.

10.1.2 Differential Settlement

Differential post-construction settlement for individual tank foundations shall notexceed the values noted in the following table.

Tank Diameter

Foundationtype toH-000-

1315-001Rev 10

TOTALSettlement

(mm)

Differential SettlementTilt

(Note 3)Edge toCentre

(Note 1)

AroundCircumference

(Note 2)

> 25m Type 1 300 D / 30013mm per 10m of

circumference(1 / 769)

H / 200

> 10m & < 25m Type 2 150 D / 30013mm per 10m of


H / 200

< 10m Type 3 50 D / 30013mm per 10m of


H / 200

D = Tank Diameter

H = Tank Shell Height


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SPECIFICATIONS FOR

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OF STORAGE TANKS



CIVIL

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Note 1: Criterion for edge (perimeter) to centre differential settlement determined fromBS EN 14015.Note 2: Criterion for circumferential differential settlement determined from API 650.Note 3: Criterion for tilt, the out of verticality of the top of the shell relative to the bottomof the shell, is taken from BS EN 14015.Note 4: The above settlement criteria must be agreed/accepted by the tankmanufacturer/contractor taking into account the specific tank configuration, roof type,etc which may dictate more stringent limits.

11. CATHODIC PROTECTION

When cathodic protection of the tank bottom is adopted, consideration shall begiven to the compatibility of the foundation surfacing material in contact with thetank floor. For guidance on compatibility refer to BS 7361: Part 1, Section 4.5 orequivalent applicable standard.

12. ADDITIONAL CONSIDERATIONS

In addition to the foregoing types of tank foundations the following items may needto be incorporated into the design:-

a) Leak detection

b) Prevention of ground contaminationc) Geotextile to protect formation level

d) Drainage of granular fill pad

13. CONSTRUCTION TOLERANCES

Construction tolerances for tank foundation shall be in accordance with BS 2654,Section 14 or equivalent applicable standard.

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