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www.HaywardBaker.com
Foundation Solutions for New TanksNISTM – 6 th Annual International Aboveground Storage Tank Conference and
Trade Show – September 19, 2013
http://www.nistm.org/index.html
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns – Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns – Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Above Ground Storage Tanks are not built on thebest sites, so they offer foundation challenges
• Soft Compressible Soils – The load is always there – Differential Settlements offer maintenance challenges – Edge stability can lead to catastrophic consequences
• Mixed bearing soils and placed fills• Foundations available
– –
– – Im prov ed Groun d
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Soft soil beneath the tank can consolidatewith time rendering the tank useless
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Lack of sufficient edge stability can create floorplate failure or buckling of shell
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What types of Ground Improvement methods aretank friendly?
• Stone Columns – Vibro Piers – Aggregate Piers – Geo Piers
• Wick Drains – Vertical Drains (PVDs) – Need surcharge + time – Using the tank for surcharge is risky
• Displacement Piles – CMCs, DeWall Piles, CSCs
•Rigid Inclusions
• Deep Dynamic Compaction• Soil Mixing – Wet and Dry Methods
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Why does Ground Improvement make sense forTanks?
• Offers faster site turnover• Predictable long term performance• Higher Tank Capaci t ies
• Controllable settlements• Usually less expensive than traditional methods• Flexible Designs
• Very good history in the USA as a widely acceptedpractice
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Arrangement of Treatment
• Typically in a square patternunder the floor of the tank
• Replacement ratios from 10to 50%
• Placement of elementsdirectly beneath the shell
• Typically settlement criteriacontrols design
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The Load Transfer Platform Must ProvideUniform Support of the Load from the Tank
• Uses a semi rigid transferplatform
• Designed to limit dishingbetween GI elements
• Crushed rock isfantastic…but sand willdo
• Layers of geogrid toincrease efficiency
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns – Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Design soil parameters used in the GroundImprovement solution for support of the tank
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Stability check is crucial to the success of thetank foundation project
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Stresses under the tank as well as overlappingstresses from other tanks must be checked
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Numerical model setup to analyze the long termperformance of the Soil Mix support system
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns – Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Vibro-Replacement or Stone Columns:reinforce the ground with aggregate
Performed in-situ up to 120 feet deep
Effective above and below the water table
Performed using wet top-feed method or drybottom-feed method
Commonly used for seismic responseimprovement
Vibro Systems
Vibrocompaction
Vibro-Replacement StoneColumns
VibroPiers / Aggregate Piers1
2
3
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Typical Boring and design from the tank side ofthe project
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• Stone Columnsdesigned to carry 2/3load from tank
• Treatment depths just
into the dense sand• Maximum center
settlement – 4 inches
• Maximum perimetersettlement – 3 inches
• Satisfies all criteria
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Hydrotest Data from Stone Column Supportedtanks…the settlement has been designed
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns – Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Dry Soil mixing methods are utilized in wettersofter soils or where REM is a problem
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Dry binder materials arepneumatically injected into thesoil during the dry mixingprocess
Bottom up method of soilmixing
There must be adequate soilmoisture for the binders tofully hydrate often limitingdesign strengths
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Dry or Wet Mixing can be used to treat 100%of the soil to form blocks
Dust
Control
BinderShuttle
24-TonTanker
GeofabricSurcharge (2-
ft)
20 ft20 ft
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Dry Soil Mixing at Port Everglades to supporttanks in organic soils
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The Project was contracted as design-build andmet the following criteria
• Design Strength – Allowable bearing capacity of 3,750 lbs/ft 2 for thein-situ soil mass
• Settlement – Planar tilting not to exceed 8 inches (100-ft
diameter), 10 inches (125-ft diameter) across thediameter of the tank
– Center-to-edge dishing not to exceed 5 inches(100-ft diameter), 6 inches (125-ft diameter)
– Out of Plane Differential not to exceed 3/8 inch inan arc length of 30 feet
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Dry mass mixing is working in block cellarrangement working from platform
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Following Mass mixing, the tank foundation canbe completed using ring beams
All tanksconstructed on
shallowfoundations
Foundation
elementsconstructed to
bear directly onsoil mix / or
compacted fill
bearing on soilmix
No relievingplatform is
required
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Following the work and after the tank is built thehydrotest is monitored from start to finish
k h d l d
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Supporting tanks with Deep Mixed Columns andMass Mixing can provide an economical solution
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C i f h S il i h fi
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Construction of the Soilcrete Mat is the first stepin the process
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Mass Mix Cap is thefirst element to beinstalled. Designthickness of 10 feet.
C l i ll d h h h il
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Columns are installed through the soilcrete matto complete the foundation system
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Columns installed in a singlepass depth of 75 feet
Th h k b i d h
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The three new tanks being constructed over thenew structural support system using Soil Mixing
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M i i h T k f ll h i h d i
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Monitoring the Tank to full height duringhydrotest
Final HydrotestHeight of 46’- 3”RingwallSettlement wellwithin APItolerances as wellas floor settlement
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Lots of Happy Tanks!
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns
– Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Wick Drains – The General Idea
Without Drains
Clay
Bedrock
With Drains
Bedrock
How are wick drains installed and how do they
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How are wick drains installed and how do theywork?
• The Drains can beinstalled to depthsgreater than 100 ft.
• Very fast installationspeeds
• The water has to go
somewhere on site!• Needs surcharge
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Presentation Outline
• Some Definitions to set the stage• Design Considerations for Supporting Tanks• Ground Improvement Tank Support Methods
– Stone Columns
– Soil Mixing – Wick Drains – Other Improvement
• Conclusions
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Dynamic Compaction for Chemical Storage
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Ground Modification for Asphalt Storage Tanks
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Conclusions
GI Method Soft Soils,Compressible Soils,
Organic Soils
Mixed Soils orUndocumented
Fills
Liquefiable Soils orClean Sands
Sandy Soils
Wick Drains Excellent-Requires Preload-May require stagedloading
Good-May require extrameasures to install-Requires Preload-May require stagedloading
N/A N/A
Earthquake Drains N/A N/A Good N/A
Stone Columns orAggregate Piers
Good-Sufficient settlementreduction may not beachievable
Very Good Excellent Excellent
Rigid Inclusions Very Good Very Good N/A Good
Soil Mixing - Columns Excellent Very Good Excellent Excellent
Soil Mixing - Mass Excellent Good to N/A-Depending on soil type
Excellent Good
h k
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Thank You!! Questions?
Dennis W. Boehm [email protected] Baker www.haywardbaker.com
509 North Sam Houston Parkway/Houston, Texas
281-668-1870
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