FOUNDATIONS AND RETAINING WALLS UPDATE...o Coulomb, δ= ⅔φ o Rankine, δ= β′ OGE Foundations and Retaining Walls Update • June 05, 2018 Method of Calculation "Horizontal" Earth

FOUNDATIONS AND RETAINING WALLS UPDATEGEOTECHNICAL CONSULTANT WORKSHOP, JUNE 05 2018

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FOUNDATIONS

AND RETAINING

WALLS UPDATEAlexander B.C. Dettloff, P.E.

State Foundations Engineer

ODOT Office of Geotechnical Engineering

OGE Foundations and Retaining Walls Update • June 05, 2018

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AASHTO LRFD 8TH EDITION (2018)

o AASHTO LRFD Highlights

(Bigger Changes)

o AASHTO LRFD Specific Article

Changes

o Other Subjects for Discussion


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o Highlights:o Section 5: Concrete Structures

o Completely New and Reorganized

o old 5.8.2.9 - Shear Stress in Concrete, is

now 5.7.2.8

o old 5.13.3 - Footings, is now 5.12.8

o old 5.13.4 - Concrete Piles, is now 5.12.9

o old 5.13.4.6 - Seismic Requirements,

moved to 5.11.3.2 and 5.11.4.5 under

new 5.11 - Seismic Design and Details


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o Highlights:o Section 6: Steel Structures

o Many new changes (94 Articles)

o 6.5.4.2 - Resistance Factors: For axial

compression, steel only φc = 0.95

(2014, 7th Ed. change)

o Section 7: Aluminum Structures

o Also many changes (69 Articles)


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o Highlights:o Coulomb Analysis of MSE Walls Ballot Item

o Formerly, Rankine with δ = β or B

o Now explicitly Coulomb, δ ≤ ⅔ ϕ

o “Horizontal” EH, LS, ES inclined at δ

o Affects the following Articles:

o 3.11.5.8.1 - Earth Pressure Distribution for

MSE Walls

o 11.10.5.2 – Loading

o 11.10.7.1 - External Stability (Seismic)


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o Article 11.10.7.1 - External Stability

o Figure 11.10.7.1-1 updated to show PAE

inclined at Coulomb δ


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o Article 3.11.5.8.1 - Earth Pressure

Distribution for MSE Walls

o For broken back slope use either:

o Generalized Limit Equilibrium (GLE)

Method (see A11.3.3),

o Coulomb Trial-Wedge Analysis (see

A11.3.1, A11.3.2), or

o “Traditional Method” per Figure C3.11.5.8.1-1 with β = β′


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o “Traditional Method”o Coulomb, δ = ⅔ φ

o Rankine, δ = β′


Method of Calculation "Horizontal" Earth Pressure Load

Limit Equilibrium Analysis 45,738 lb/ft

Coulomb Trial-Wedge Analysis 46,072 lb/ft

Coulomb "Traditional" Method 52,734 lb/ft

Rankine "Traditional" Method 53,012 lb/ft

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o Highlights:o Seismic Wall Corners Ballot Item

o No longer requires seismic analysis for

walls with changes in alignment

sharper than 120 degrees, but calls

attention to why these changes in

alignment are problematic:


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o (they “tend to exhibit greater damage

than free standing walls with generally

straight alignments due to potentially

greater stiffness at the corner, or may

separate at the corner due to lack of

connectivity between wall sections at

the corner.”)


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o Affects the following Articles:

o 11.5.4.2 - Extreme Event I, No Analysis

o 11.6.5.6 - Wall Details for Improved

Seismic Performance

o 11.10.7.4 - Wall Details for Improved

Seismic Performance

o 11.11.6 - Seismic Design for Prefabricated

Modular Walls


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o Formerly no guidance provided on what

specific analyses should be conducted

to address the potentially higher loads,

nor is any such guidance available.

Therefore, these articles have been

refocused to provide better guidance

on what is expected for good seismic

detailing.


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o Also calls attention to the fact that

placement and compaction of fill at

corners requires more attention than

other sections along the wall due to

lack of room there. Inadequate

compaction can potentially cause

increased deformations at the corners

during a seismic event.


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o Specific Article Changes:o 3.8.1.2.1 - Wind Load on Structures: WS

o For Ohio, Design Speed V = 115 mph

o Load Factor γWS = 1.00

o Generally, design pressure ≈ 0.07 ksf

o Formerly, V = 100 mph, γWS = 1.40

o Formerly, design pressure ≈ 0.05 ksf

o 1.40 × 0.05 = 0.07 (no change)


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o Specific Article Changes:o 3.11.5.3 - Active Lateral Earth Pressure

Coefficient, ka

o δ = 0.67 ϕ soil-concrete, soil-soil

o δ = 0.33 ϕ soil-steel

o δ = 0.50 ϕ * soil-precast concrete

o δ = 0.70 ϕ * prefabricated modular

stepped modules

* per Table C3.11.5.9-1


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o Specific Article Changes:o 3.11.5.6 - Lateral Earth Pressures for

Nongravity Cantilevered Walls

o For Figures 3.11.5.6-3, 3.11.5.6-6, and

3.11.5.6-7 (Teng, 1962) , D = 1.2 Do

o Explicitly states that adding 20% to

depth is due to a simplification of the

loading model.


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o Specific Article Changes:o 3.11.6.2 - Point, Line, and Strip Loads

(ES) Walls Restrained from Movement

o For Figure 3.11.6.2-4 - Horizontal

Pressure on a Wall Caused by a Finite

Line Load Perpendicular to the Wall;

redefinition of X2 to be in-line with the

original Boussinesq definition.


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o Specific Article Changes:o 10.6.3.1.2c - Considerations for Footings

on Slopes

o Formerly no convergence of Nc

(to 5.14 or drained value for flat slope)

o Now use Tables for RCBC

o qn-sloping ground = RCBC qn

o or use Limit Equilibrium


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qn = c′f Ncm + γq Df Nqm Cwq + 1/2 γf B′ Nγm Cwγ (AASHTO LRFD Eq. 10.6.3.1.2a-1)

B′ = B = 8 ft L = infinite (strip footing)

φ′f = 22° c′f = 150 psf

γf = 120 pcf γq = 120 pcf

sc = sq = sγ = 1.00 (for infinite strip footing)

ic = iq = iγ = 1.00 (for inclined eccentric loading)

dq = 1 + 2 tan(ϕf)(1-sin ϕf)2 arctan(Df/B′) (Hansen, 1970)

Nc = 16.88 Ncm = Nc sc ic = 16.88

Nq = 7.82 Nqm = Nq sq dq iq

Nγ = 7.13 Nγm = Nγ sγ iγ = 7.13

Cwq = 1.00 (deep water, Dw > Df) Cwγ = 1.00 (deep water, Dw > Df + 1.5B)

Df dq Nqm qn

0 ft 1.00 7.82 5954 psf

3 ft 1.11 8.71 9090 psf

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B/H = 1.0 1.0 1.0b/B = 0.5 0.5 0.5Ns = 6.4 4.0 4.0β = 20° 20° 20°φf = 22° 20° 30°RCBC = 0.78 0.79 0.74

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qn-sloping ground = RCBC qn = 0.78 x 5954 psf = 4644 psf

Df dq Nqm qn qn-sloping ground

0 ft 1.00 7.82 5954 psf 4644 psf

3 ft 1.11 8.71 9090 psf N/A

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qn-sloping ground = RCBC qn = 0.719467 x 5954 psf = 4283 psf

Df dq Nqm qn qn-sloping ground

0 ft 1.00 7.82 5954 psf 4283 psf

3 ft 1.11 8.71 9090 psf N/A

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Method Top of Slope Middle of Slope Flat Ground

RCBC Table 4644 78% 4283 72% 5954

Limit Equilibrium 4720 65% 4096 56% 7315

Percent Difference 2% 4% 23%


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Method Top of Slope Middle of Slope Flat Ground

RCBC Table N/A N/A 9090

Limit Equilibrium 7404 71% 7869 75% 10500

Percent Difference N/A N/A 16%


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o Specific Article Changes:o 10.6.3.4 - Failure by Sliding

o No more δ, replaced explicitly with ϕf.

o Now, Rτ = CV tan ϕf.

o C = 1.0 for CIP, C = 0.8 for precast

o For cohesive, rewrote so that footings

on clay are always on 6 in. granular

material, and 0.5 σ′v is not only a limit

when the granular material is present.


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o Specific Article Changes:o 11.8.4.1 - Overall Stability

o Commentary states the design

procedure applied to Figure 3.11.5.6-3

(Teng, 1962) is for continuous walls

embedded in granular soils.

o States that similar procedures may also

be performed for temporary walls

using Figures 3.11.5.6-6 and 3.11.5.6-7

(Teng, 1962).


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OTHER SUBJECTS FOR DISCUSSION

o Precast Wingwall Alternatives

o Prefabricated Modular Walls

o Predrilled Piles in Bedrock

o MSE Walls (various subjects)

o CCTV Tower Foundations

o Downdrag on Piles


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OTHER SUBJECTS FOR DISCUSSION

o Settlement Time

o Spread Footing Foundations

in BDM versus L&D Manual

o Micropiles

o Monotube Piles


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PRECAST WINGWALL ALTERNATIVES

o Typically two options:


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o Plan Note D118:o Item 511 Wingwalls or Headwalls for 611

Items

“For Items 706.05, 706.051, 706.052 and

706.053 with a cast-in-place wingwall or

headwall a precast alternative may be

furnished per 602.03. The precast

alternative will meet the cast-in-place

structural design loadings, design height,

and design length dimensions.

… (continued)


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o Plan Note D118:o Item 511 Wingwalls or Headwalls for 611

Items

…

Full compensation for the precast

wingwall or headwall is the number of

cubic yards of Item 511 and pounds of

Item 509 for the corresponding cast-in-

place structure.”


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o Plan Note D118 pulled and

revised:o No permanent tension on epoxy anchors

o Limit on angle between stream and walls

with no stem-footing moment connection

o Requirement of engineered drawings

including: backfill details, sequence of

construction, any changes to footing

o Payment quantity a lump sum


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o Precast Semigravity Wall

suppliers encouraged to submit

to Prefabricated Retaining Wall

Systems Approval Process.

o Pre-Approval will be required

within the next couple of

years.


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PREFABRICATED MODULAR WALLS

o Prefabricated Modular Wall

Supplemental Specificationo Currently SS 840 provides design and

construction specification for MSE Walls

o Need new SS ### for Prefabricated

Modular Walls, to provide design and

construction specifications, so wall

systems can be submitted to the

Prefabricated Retaining Wall Systems

Approval Process on an even basis.


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o Prefabricated Modular Wall

suppliers encouraged to submit

to Prefabricated Retaining Wall

Systems Approval Process.

o Pre-Approval will be required

within the next couple of

years.


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o Prefabricated Modular Walls

Includeo Segmental (Modular Block) Walls

o (Dry-cast concrete modular systems will not

be allowed for highway construction)

o Large Gravity Block Walls

o Crib Walls

o Bin Walls

o Gabion Walls, per SS 838 (no preapproval)


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PREDRILLED PILES IN BEDROCK


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o Predrill (pre-bore) hole to

larger diameter than pileo Item 507 Prebored Holes, As Per Plan

o Place H-pile in holeo Item 507 Steel Piles HP__x__, Furnished

o Concrete Pile to Top of Rocko Use Class CQ Misc. Concrete

o Concrete included in Prebored Holes


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o Backfill to bottom of pile capo If MSE Wall, sleeve pile and use granular

fill per SS 840.03.K (include in MSE Wall)

o Otherwise:

o If conventional abutment, use LSM

o If integral abutment, use granular

o Backfill included in Prebored Holes Item


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o Design Points:o Order Length: Do not add an additional 5’

to Estimated Length

o Piles Furnished, As Per Plan

o Includes placement in prebored hole

o No Item 505 Pile Equipment Mobilization

o No Item 507 Piles Driven (no driving)

o Can use φc = 0.95 for steel only column in

axial compression


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MSE WALL DESIGN CONSIDERATIONS

o MSE Wallso Acute angle limits for temporary

construction

o Bearing elevation, sliding considerations

with granular undercut

o Two-stage construction

o Staged demolition: slope w/ short wire-

faced wall rather than tall wall


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o Acute angle limits:o For permanent construction, no acute

corner angles (under 90°) allowed

o For temporary construction (wire-faced

MSE walls) acute angles to 45° allowed

o Acute angles must be buried or

demolished at end of construction

o If sharper acute angles are required for

MOT, then MSE walls cannot be utilized


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o MSE granular undercut o Deeper granular undercut than standard

SS 840.06.D foundation preparation is

sometimes utilized

o This does not change the foundation

material to Granular Material Type C

o Bearing is calculated at bottom of

undercut with deeper embedment

o Sliding is also calculated at bottom of

undercut with passive resistance


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o MSE granular undercut


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o Two-stage MSE Walls


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o Two-stage MSE Walls


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o Two-stage MSE Wallso Avoid galvanic corrosion (bimetallic

corrosion) in the connectors

o All metallic components hot-dip

galvanized or epoxy coated

o Avoid macrocell corrosion between

backfill and wall face

o Assure low chloride and sulfate content of

all wall backfill

o Provide drainage protection for connector

zone


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o Staged bridge demolition


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o Staged bridge demolition


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CCTV TOWER FOUNDATIONS

o Office of Traffic Operationso Have installed numerous poles (several

hundred?) around the state over the last

several years

o CCTV Camera on top of 70-foot tall spun

precast concrete pole

o For camera stability, Serviceability

requirement of less than one inch

deflection at top of pole in 30 mph wind


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o Service Limit State Controlso Still, check Strength Limit State at 100

mph wind

o Strength Limit State Design by Broms

Method, per “Design of Laterally Loaded

Piles” (Broms, 1965)


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DOWNDRAG ON PILES

o Downdrag on Piles(Service versus Strength)

o Friction Piles are driven into the ground,

continuously deforming the soil at the

base, and sliding along the side soil.

o Full geotechnical capacity (minus any

setup) is mobilized at driving.

o If the axial load exceeds this value, the

pile will move again, remobilizing the full

geotechnical capacity.


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DOWNDRAG ON PILES

o Typical 12-inch CIP Pipe Pile,0.25” shell, 60 feet long, 35 ksi Steel

o 676.1 kips Nominal Axial Structural

Resistance

o Say, ultimate resistance is tip = 20 kips +

side = 260 kips = 280 kips total (geotech.)

o Say, settlement occurs in top 30 feet,

neutral plane at 20 feet.

o Friction in upper 20 feet = 80 kips

o Resistance below 20 feet = 200 kips


86 |

DOWNDRAG ON PILES


0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

Dep

th (

feet

)

Axial Resistance (kips)

Ultimate Geotechnical Resistance Bridge Load

= 220 kips

Downdrag

= 80 kips

Total Load

= 300 kips

> Total

Resistance

= 200 kips

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DOWNDRAG ON PILES

o Structural Resistance?o Total Load = 300 kips < 676.1 kips OK

o Geotechnical Resistance?o Total Load = 300 kips > 200 kips No Good

o But will the Pile Fail?o Depends on definition of “failure”

o Structurally, it is okay

o Geotechnically, it will move

(Service Limit State)OGE Foundations and Retaining Walls Update • June 05, 2018

88 |

DOWNDRAG ON PILES


0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

Dep

th (

feet

)


Ultimate Geotechnical Resistance Bridge Load

= 220 kips

Downdrag

= 80 kips

Total Load

= 300 kips

> Total

Resistance

= 200 kips

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DOWNDRAG ON PILES


Bridge Load

= 220 kips

Downdrag

= 30 kips

Total Load

= 250 kips

= Total

Resistance

= 250 kips

0

10

20

30

40

50

60

70

0 50 100 150 200 250 300

Dep

th (

feet

)


Ultimate Geotechnical Resistance

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DOWNDRAG ON PILES

o Pile will stop moving when

neutral plane climbs to point

where:

bridge load + downdrag load =

total resistance

o Pile only needs to move a small

distance for this to happen

(around 1 cm = 0.4 inch)OGE Foundations and Retaining Walls Update • June 05, 2018

91 |

DOWNDRAG ON PILES

o Total Pile settlement will be

settlement of soil below

neutral plane + ≈0.4 inch

o This is a Service Limit issue

o See Amal Goza at OTEC 2018o See GEC 12 FHWA-NHI-16-009

o See MnDOT Geotechnical Manual


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SETTLEMENT TIME

o Settlement Time:o A profile of settling soil is typically

divided into multiple layers with differing

consolidation characteristics:

o layer thickness

o overburden pressure

o maximum past pressure (OCR, virgin)

o drainage paths

o cc, cr, C′, cv (magnitude and rate)


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SETTLEMENT TIME

o Some layers will take a long time to

consolidate, and some will do so nearly

immediately.

o The slowest layer does not control the

time to achieve consolidation (waiting

period), i.e. 90% or 0.4” remaining.

o Consider all layers individually, and then

build a composite of behavior.

o Consider the following 50-foot profile:


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SETTLEMENT TIME


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SETTLEMENT TIME


0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45

0.0 50.0 100.0 150.0 200.0 250.0

Rem

ain

ing S

ett

lem

ent

(in)

Days

Layer 3

Layer 4

Layer 5

Layer 6

Layer 7

Layer 8

Layer 9

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SETTLEMENT TIME


0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.0 50.0 100.0 150.0 200.0 250.0

Rem

ain

ing S

ett

lem

ent

(in)

Days

Layer 3

Layer 7

Layer 8

Layer 9

97 |

SETTLEMENT TIME

o Determine the amount of settlement

completed and remaining for each layer

at specific time intervals.

o At each time interval, sum the settlement

completed and remaining for all layers,

and plot this result versus time.

o Determine the T90 time for the entire soil

profile.


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SETTLEMENT TIME

o If the total settlement remaining at the

T90 time is greater than 0.4 inches, then

use the T90 time for the waiting period,

rounding up to an even interval of

days/weeks/months.

o If the total settlement remaining at the

T90 time is less than 0.4 inches, then find

the time at which 0.4 inches remains, and

use this time for the waiting period, once

again rounding up to an even interval of

days/weeks/months.


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SETTLEMENT TIME


0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

0 5 10 15 20 25 30 35 40 45 50

Rem

ain

ing S

ett

lem

ent

(in)

Days

All Layers

All Layers

100 |

BDM VS L&D MANUAL: SPREAD FOOTINGS

o BDM vs L&D Manual regarding

Spread Footing Foundations

o Multiple-span three-sided culverts are

considered as bridges


Spread Footings

on Soil

Spread Footings

on Erodible Rock

Spread Footings

on Non-Erodible Rock

Driven Pile

Foundations

Bridges (BDM) X 7' below ThalwegElevation

On Rock,Dowels for Lateral

202.2.3.2.h

Three-Sided Culverts (L&D Vol.2)

See OGEHEC-18, HEC-23

HEC-18, HEC-23 HEC-18 BDM, HEC-23

101 |


o BDM Spread Footings on Rocko BDM Section 202.2.3.1.b is strict on

scour resistant (non-erodible) rock:

o Qu ≥ 2,500 psi (“slightly strong” rock)

o Remain intact when immersed in water

(e.g. insoluble) no bucket slaking

o Unit weight ≥ 150 pcf

o Joint or bedding plane spacing that

define large blocks (> 4-ft)


102 |


o BDM Spread Footings on Rocko BDM Section 202.2.3.1.b eliminates nearly

all rock in Ohio as non-erodible

o We propose to change the erodibility

requirements to HEC-18, FHWA-HIF-12-003

o Erodibility Index for strong and durable

rocks (Quarrying and Plucking)

o Abrasion Scour of rock due to bedload

o We still need to define the use of these

for Ohio


103 |


o HEC-18 Scour of Soilso Granular Soils: τc (Pa) = D50 (mm)

o Holds down to D50 ≈ 0.1 mm


104 |


o HEC-18 Scour of Soilso Cohesive Soils not so straightforward


105 |


o FHWA-HRT-15-033 “Scour in

Cohesive Soils”


106 |


o Erosion Rate (Briaud, 2011)


107 |




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o HEC-23, FHWA-NHI-09-112,

Bridge Scour and Stream

Instability Countermeasures


111 |

MICROPILES

o Micropileso Typically used for:

o Underpinning Inadequate Foundations

o Supplementing Existing Foundations

o Adding Lateral Stability

o Tight Overhead Working Conditions

o Generally not a cost-effective new-build

foundation option


112 |

MICROPILES

o Design Micropiles per:o AASHTO LRFD Bridge Design Specifications

Article 10.9 (LRFD)

o and AASHTO LRFD Bridge Construction

Specifications Section 33 (LRFD)

o or FHWA-NHI-05-039 “Micropile Design

and Construction Reference Manual”

(ASD)


113 |

MONOTUBE PILES


114 |

MONOTUBE PILES

o Monotube Pileso Monotube Pile Corporation out of business

o Removing vertical fluting, circumferential

corrugations, and tapered piles (B,C,D)

from 507.06

o No more replacement of CIP Pipe piles

with different types in construction

o No way to track these replacements, and

evidence shows they do not necessarily

perform the same (open to claims)


115 |

MONOTUBE PILES

o Miscellaneous Pileso We rarely (if ever) use the piles being

removed from 507.06

o However, future plan is to add a section

to C&MS 507 for Miscellaneous Piles,

including: Timber, Tapered, Fluted,

Corrugated, and Precast Concrete

o For now, these pile types can still be

specified under 507E98000 PILING, MISC.:

with appropriate plan notes


116 |

MONOTUBE PILES

o DRIVEN Monotube Pile modelo Allows negative cumulative side friction

(physically not possible)

o Slight Taper does not approach behavior

of straight pile

o Magnifies granular side frictional effects

in the taper length approximately 2.25x

o Often underpredicts length substantially

o ODOT will disallow use of this analysis

model for design


117 |

MONOTUBE PILES

o Monotube Pile analysiso Analyze as standard CIP Pipe Pile at

diameter of straight (non-tapered) part

o Add an additional 5 feet to Estimated

Length (beyond CIP Pipe Estimated)

o Ensure tapered length starts a minimum

of 5 feet below ground surface or pile cap

o Monotubes are fluted tapered piles, but

this also applies to smooth tapered piles

o Does not apply to Raymond tapered piles


118 |

?

QUESTIONS

Last updated 6/15/2018


Documents

FOUNDATIONS AND RETAINING WALLS UPDATE...o Coulomb, δ= ⅔φ o Rankine, δ= β′ OGE Foundations and Retaining Walls Update • June 05, 2018 Method of Calculation "Horizontal" Earth