introduction to geopier system

INTRODUCTION TOGEOPIER®SYSTEM

Mr. Gerry Kehler, PE (Georgia)Mr. Tommy WilliamsonApril 14, 2010

OUTLINE

1. History of Foundation Support

2. Geopier System Construction

3. Engineering Basics

4. Different soil types

5. Limitations

6. Industrial Applications

7. Case study

Two choices:

History of foundation systems

1. Shallow 2. Deep

Good soil

BadsoilGood

soil

OK soil

In early 1990’s a third choice emerged:Intermediate Foundation® systems

1. Shallow 2. Deep 3. Intermediate

Good soils

OK soil

Badsoil

Good soil

OK soil


The Geopier® Systems are made up of Rammed Aggregate Pier® elements.

With time, the Geopier System gained popularity with cost and schedule benefits.


1. Created by forming a cavity

Rammed Aggregate Pier Construction

2. Adding thin lifts of Aggregate, and


3. Vertically RAMMING the thin lifts of aggregate


Temporary casing used to stabilize caving soils


Displacement Construction

Displacement Construction

Then, as hollow

mandrel is

raised, stone

flows from

hopper down

through mandrel.

Impact

hammer

After

driven

to full

depth,

mandrel

is raised

up 3 ft

Then

driven

back

down 2

ft

Dense,

1 ft lifts

Crowd pressure

from rig weight

and hydraulics

First, mandrel

is driven to

full depth,

with sacrificial

cap covering

tamper foot.

Footing Construction

• Excavate for footings• Compact footing bed• Place steel• Pour concrete

Types of Foundations Supported

• Isolated Spread footings

• Continuous footings

• Retaining Walls

• Lightly loaded slabs

• Heavily loaded slabs

• Uplift Anchors

Flexible Continuous Footings

The keys to success are:

1. Vertical RAMMING (to achieve very low void ratio) and

2. Increase in lateral effective stress from the beveled tamper foot

Geopier System Features

Beveled tamper

Geopier System Features

• High allowable bearing capacity

• Control settlement

• Uplift resistance

• Lateral load resistance

How do RAP systems work?

Engineering basics

Push down on footing, the stiff element (pier) takes more of the load

How do RAP systems work?

The strength and stiffness of the pier determined using a Modulus Test which gives you a spring constant

Engineering basics

• Deflection = 0.25-inch• kg = stress / deflection = 500 pci

0.00

0.25

0.50

0.75

1.00

0 10 20 30 40

Top deflection

RAP Stress (ksf)

Deflection (in)

Telltale deflection

Design(a)

(b)

Uplift anchors required to resist tensile loads

Steel Plate

Cylindrical shearingsurface

Threaded rods

Uplift Resistance

Load Test Uplift Element at UC Davis Production Uplift Elements

Uplift Resistance

Lateral Resistance

RAP and Soil Types

• Sand, silty/clayey sand, gravel

(SP, SW, SM, SC, GW, GP)

• Clays and silts

(CL, ML)

• Peats and organics

(PT, OL)

• Undocumented fill

GEOPIER LIMITATIONS

• Extreme loads on extremely soft soils

• Sinkholes

• Expansive / swelling clay

• Obstructions during drilling

Economics:

Often provide a 20% to 40% cost savings in comparison with Deep Foundations when:

• High capacity > 75 tons and length > 30 feet

• Moderate capacity > 40 to 60 tons and length > 20 feet

• Low capacity < 40 tons and any length

Pile length

Pile capacity

RAP provides MORE economy

RAP provides LESS economy

When To Consider RAP Systems

Economics:

Often provide a 20% to 40% cost savings in comparison with over-excavation and replacement when:

• The depth of overexcavation exceeds 5 - 8 feet.

When To Consider RAP Systems

Geopier SystemApplications

Building Foundation Support

Industrial & Tank Support

Floor Slab Support Transportation

• Five story parking deck

• 63,000 sf footprint

• 77 columns with loads

ranging from

200 to 1220 kips

• Foundation options for

RAPs and auger cast

piles

CASE STUDY

VICTORYLAND PARKING DECKSHORTER, ALABAMA

SUBSURFACE PROFILE

LOWER ZONE

1220 KIPS

0.000

0.200

0.400

0.600

0.800

1.000

0 5,000 10,000 15,000 20,000 25,000 30,000

Applied Geopier Stress (psf)

Deflection (inches)

Bottom of Geopier

Top of Geopier

Unload

Modulus test results

VICTORYLAND PARKING DECK

Measured Upper Zone Settlement = 0.3”

Estimated Lower Zone Settlement = 0.2”

Total Settlement = 0.5”

530 RAP elements installed in 11 days!

VICTORYLAND PARKING DECK

Elements reinforce soft and compressible soils for support of relatively thin floor slabs.

Replace structural floor slabs on piles.

FLOOR SLAB SUPPORT

Design Considerations

FLOOR SLAB SUPPORT

Geotechnical (settlement, etc)

Structural (slab design, etc)

FLOOR SLABS - GEOTECHNICAL

Fill and floor slab support

d

spacing (s)

"competent"

soils

Soft, compressible

soils

Floor load (p)

New Fill

45o

Thickness

RAP

element

(t)

Arching transfers pressures to pier

FLOOR SLABS – STRUCTURAL

Steel Reinforcement

. . . . . May be required to resist tensile stresses within top of slaboverlying Geopier elements.

Need to:

-Work closely with structural engineer

- Perform finite element analysis

(project SE or GFC SE)

Results of analysis identify areas of higher bending stresses

Indicate whether added reinforcement or thicker slab is needed

Finite Element Analysis (FEA)

FLOOR SLABS – STRUCTURAL

FLOOR SLAB SUPPORT

Boeing Building 101, St. Louis, MODelta Marine, Seattle, WA

Costco Retail Store, Tacoma, WA Polaris Plant, Vermillion, SD

KRAFT CAPRI-SUN WAREHOUSE GRANITE CITY, ILLINOIS

Kraft Capri-Sun Warehouse

Granite City, Illinois

St. Louis, MO

FLOOR SLABS - EXAMPLE

Floor Slab700 psf pressure

5 ft fill to get out of floodplain


10 ft

CH & CL, Su = 500 psf

0 10 20 30 40

SP, SM

N-values, M%Subsurface conditions


Soft Clay

Dense Sand and Silty Sand

Soft ClayFloor Slab

•Winter construction

• Groundwater

Fill

Planned construction

10 ft


OPTIONS?

Rammed Aggregate Pier stabilized zone

Floor Slab

Dense Sands and Silty Sands

Value engineering proposal

Pier spacing = 14 ft


-2.50

-2.25

-2.00

-1.75

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

0 4000 8000 12000 16000 20000 24000 28000

top of Geopiermiddle telltalebottom telltale

Geopier Stress (psf)

Deflection (in)

15

Modulus test


-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

12/6/00

12/11/00

12/16/00

12/21/00

12/26/00

12/31/00

1/5/01

1/10

/01

1/15

/01

Settlement Monitoring

Settlement (in)

Time (days)

Pier = 0.5 in (0.6)

Soil = 0.6 in (0.6)

Differential = 0.1 in (0 in)

Differential settlement


FLOOR SLAB SUPPORT

• 360,000 sq. ft. manufacturing facility addition

• Floor slab pressures = 700 psf

• 2,100 Geopier elements installed in one month

Mirant Power Plants, MD

POWER GENERATION

Morgantown Plant

Mat foundation:91-ft x 357-ft

Absorber stacks and building

Design pressures:3 ksf at building6 ksf at stacks

Nanjemoy Formation (N > 30)

ML (N = 8 – 20 bpf)

SM (N = 3 – 15 bpf)

14’

Excavation

18’

~26’Impact RAPs:4 to 6 ft o-c

Est. settlements:~ 2.5 inches

Chalk Point Plant

Mat foundation:87-ft x 219-ft

Absorber stacks and building

Design pressures:3 ksf at building6 ksf at stacks

Impact RAPs:4 to 6 ft o-c

Est. settlement:~ 3.8 inches

Nanjemoy Formation (N > 30)

MH (N = 11 – 26 bpf)

SM (N = 5 – 11 bpf)

17’

40’

~26’

Excavation

TANK SUPPORT

Bearing Capacity

Unsuitable Soil

Competent Soil

DESIGN ISSUES

DESIGN ISSUES

Settlement

Unsuitable Soil

Competent Soil

DESIGN OPTIONS

Overexcavation and Replacement

Problems• High groundwater• Cost• Schedule

DESIGN OPTIONS

Pile-supported concrete pad

Problems• Cost• Schedule

DESIGN OPTIONS

Granular pad over Geopier reinforced zone

Geopier

Reinforcement Zone

SAMPLE INDUSTRIAL PROJECTS

• Houston Fuel Oil Terminal Tank Support

• Kinder Morgan Tank 150-27 Repair

• Valero Refinery Tank TK-443

• Lyondell-Citgo Tank Repair

• Kinder Morgan Tank 150-44

• Valero Refinery Tank TK-231

• Industrial Zeolite Plant

• ExxonMobil Tank 2176 Repair

• ConocoPhillips Refinery

• New tank construction

• 125-foot diameter

• 48-ft tall

• Design pressure = 3 ksf

CASE HISTORY:VALERO REFINERY TANK TK-231HOUSTON, TX

4 ft

Su (ksf)

0 1.0 2.0 3.0

Clay Fill0 ft

SUBSURFACE CONDITIONS

4.0

V. Soft to Firm Clay

Firm to V. Stiff Clay

10 ft

GEOPIER SOLUTION

Perimeter Differential Settlement Control

Fill

Soft Clay


GEOPIER SOLUTION

Bearing Capacity – Edge Instability

V. Soft to Firm Clay


Geopier

FS for Geopier-reinforced soil = 1.30

Modulus Load Test Results

-2.00

-1.50

-1.00

-0.50

0.00

0 5 10 15 20

Top of Geopier

Telltale No. 1

Top of Geopier Stress (ksf)

Deflection (in)

Design Stress

Deflection

GEOPIER SOLUTION

Settlement = 0.5 in at design stress

• Installed 243 piers in 8 days (30 piers / day)

• Increased edge stability (FS = 1.3)

• Limited perimeter differential settlements

GEOPIER SOLUTION

• Duke Energy

• Ameren (UE)

• Motiva

• Lockheed

• ExxonMobil

• Valero

• Nucor Steel

• General Motors

• BNSF

• Kinder Morgan

• Boeing

• U.S. Food Services

Selected National Clients

• Certainteed

• Kraft

• John Deere

• Case New Holland

• Pfizer

•Wal-Mart

• Michelin

• Maybelline

• Pacific Bell

• Sara Lee

• Anheuser Busch

• General Mills

Shear reinforcement in Geopier zone

TRANSPORTATION APPLICATIONS

US-90 & SH-6 Intersection Upgrades, Sugarland, Texas Site Plan

SCOPE OF WORK

6.7 / 22107 / 353South Ramp

7.3 / 24107.6 / 353North Ramp

8.2 / 2769 / 227South

Abutment

7.3 / 2479 / 260North

Abutment

Max. Height

(m)/ [ft]

Length

(m)/[ft]

MSE Wall

Location

Typical Soil Conditions

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 w%

Depth (m)

GWT

CL

SM

SM, SW

φ' = 22°

c' = 4.8 kPa

φ' = 30°

c' = 0

cεc = 0.11 - 0.14

cεr = 0.03 - 0.05

φ' = 30°c' = 0

0 10 20 30 40 50 60 70 80 90

North Ramp South Ramp

North Abutment South Abutment

Su (kPa)

CL

SM

Geopier Installation

•Total Number of Piers = 1411 •Two Crews •20 to 25 RAPs•Cost ~ $1,000,000•Bid Through DOT letting•FHWA funded the geotechnical instrumentation

Modulus Test Results

-60-55-50-45-40-35-30-25-20-15-10-50

0 300 600 900 1200 1500

Top-of-Rammed Aggregate Pier Stress (kPa)

deflection, (m

m)

North Abutment

South Abutment

South Ramp

South Ramp II

North Ramp

Design Stress < 18000 psf< ¾-in top vertical deflection

Geotechnical Instrumentation Layout

Near the Bridge Abutments at general locations of higher bearing pressure

MonitoringStation 1

MonitoringStation 2

East

West

Geotechnical InstrumentationHorizontal and Vertical Inclinometers

Vibrating Wire Piezometers

Sondex Settlement System

Instrumentation Installation

Vibrating Piezometer Cable

Horizontal InclinometerCasing w/Cable Return

ProtectiveInstrumentationBox

Instrumentation Monitoring Results

Horizontal and Vertical InclinometersPiezometer Nest

South Ramp Monitoring Station-1

0

4

8

12

16

20

24

11/29/05

12/27/05

1/24/06

2/21/06

3/21/06

4/18/06

5/16/06

6/13/06

7/11/06

8/8/06

9/5/06

10/3/06

10/31/06

11/28/06

12/26/06

Date

Pore Pressure (psi)

0

2

4

6

8

10

12

Fill Pressure (psi)

-15 ft

-20 ft

-24 ft

-30 ft

Fill

Spike Caused by Driving of Pile within 5 ft of Piezometers Gradual Rise in

Pore Pressure Caused by General Rise in Groundwater Elevation

Instrumentation Monitoring Results

Sondex Settlement System- South Ramp-West

-0.60-0.50-0.40-0.30-0.20-0.100.000.100.200.300.400.50

0 5 10

15

20

25

30

35

40

45

50

Depth-(ft)

Downward Movement (ft)

1/27/2006

1/25/2006

1/26/2006

2/1/2006

2/9/2006

2/20/2006

2/23/2006

3/2/2006

3/9/2006

4/6/2006

5/4/2006

7/12/2006

9/19/2006

10/24/2006

Avg

2.5-in (6.4-cm)

Instrumentation Monitoring ResultsVertical Inclinometers at North Ramp

0

5

10

15

20

25

30

35

40

45

50

-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0

Lateral Movement (in)

Depth (ft)

North Ramp-Sta.2-West

North Ramp Sta. 2 - East

North Ramp-Sta.1-West

North Ramp Sta. 1-East

11/2006 through 5/2007

Bottom of Retaining Wall Footing

2.54-cm

NORTH ABUTMENT

NORTH RAMP

SOUTH ABUTMENT

SOUTH RAMP

Conclusions

-Vertical Settlement 2.5 to 3-inches

-Horizontal Displacement < 1.5-inches

-Rapid Pore Water Pressure Dissipation

Afforded by Radial Drainage into RAPs

-Vertical Displacement < 2-inches

Post-Construction

- Complied with FHWA requirements

Questions?

introduction to geopier system

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