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Page 1 IDOT Pile Design Training Handout Training on Bridge Pile Design by Spreadsheet April 2021 Michael Nop, PE 515-239-1233 [email protected] Iowa DOT, Bridges and Structures Bureau

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Page 1: IDOT Pile Design Training Handout

Page 1

IDOT Pile Design Training Handout

Training on Bridge Pile Design by Spreadsheet

April 2021

Michael Nop, PE 515-239-1233 [email protected] Iowa DOT, Bridges and Structures Bureau

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TABLE OF CONTENTS County Problem 1A J30 - Integral Abutment - HP10x42, Modified IDOT ENR Formula, Cohesive Soil 3 County Problem 1B J30 - Integral Abutment - HP10x42, WEAP, Cohesive Soil, Setup 8 County Problem 2 H30 - Integral Abutment - HP10x57, WEAP, Cohesive Soil, Downdrag, Bedrock 10 County Problem 3 H30 - Pile Bent - HP14x73, WEAP, Non-cohesive Soil, Scour 16 Appendices

A. Friction and End Bearing Soil Charts 22 B. Soil Categories 24 C. Recommended Pile Penetration 25

DISCLAIMER: Neither the State of Iowa, the Iowa Department of Transportation nor their employees make any representations or warranties, express or implied, with respect to the use of or reliance on the data provided herewith, regardless of its format or means of transmission. There are no guarantees or representations to the user as to the accuracy, currency, completeness, suitability or reliability of this data for any purpose. THE USER ACCEPTS THE DATA "AS IS" AND ASSUMES ALL RISKS ASSOCIATED WITH ITS USE. The Iowa Department of Transportation assumes no responsibility for actual, consequential, incidental, special or exemplary damages resulting from, caused by or associated with any user's reliance on or use of this data, even if appraised of the likelihood of such damages occurring.

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County Problem 1A J30 - Integral Abutment - HP10x42

Modified IDOT ENR Formula, Cohesive Soil J30-06 Continuous Concrete Slab (CCS) Bridge Standards (https://iowadot.gov/bridge/standards/english/j30-06.pdf)

• 30’ roadway width • 0° skew • 140’ long bridge • 3 Spans: 42.5’ – 55’ – 42.5’ • Integral abutment • Pile type: HP10x42 • 10’ prebore required • Pu = 92.3 kips per pile • Generalized Soil Category: Cohesive • Construction Control: Modified IDOT ENR Formula

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ALL PILING HP10x42.

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Page 5 Standard Sheet J30-34-06

Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.2.6.1-1

(https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf) for an HP10x42 is 179 kips of nominal resistance. The factored resistance is (0.60)*(179 kips) = 107.4 kips which should be and, in fact, is greater than Pu = 92.3 kips.

Standard Sheet J30-34-06

Note: The above statement is in conflict with the statement in the J-standards on sheet J30-01A-6 which

prohibits the use of these standards when rock is less than 15 feet from the bottom of the footing – see next page. Note that both statements conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x42 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf).

Pu = (646 k)/(7 piles) = 92.3 kips per pile

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Standard Sheet J30-01A-06, GENERAL NOTES

Note: The above statement is in conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which

requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x42 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf). BDM Table 6.1.6.1.1.1-1 contains the full range of values for various conditions.

A reference to CADD note E177 is made in the plan notes above, but this note is no longer available in the BDM and is not required in the plan set.

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Soil Profile at West Abutment

Ftg Bot Elev 933

Prebore Elev 923

10’ prebore

Final ground surface

Existing ground surface

11’

Surface Elev 937

30’

Soft Silty Clay

Silty Sand

Firm Glacial Clay

Very Firm Glacial Clay

2’

9’

10’

Layer Elev 917

Layer Elev 907

Layer Elev 926

Fill

N = 4

N = 6

N = 12

N = 20 35’

Boring Bot Elev 872

SPT N values are in units of blows per foot

4’

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County Problem 1B J30 - Integral Abutment - HP10x42

WEAP, Cohesive Soil, Setup J30-06 Continuous Concrete Slab (CCS) Bridge Standards (https://iowadot.gov/bridge/standards/english/j30-06.pdf)

• 30’ roadway width • 0° skew • 140’ long bridge • 3 Spans: 42.5’ – 55’ – 42.5’ • Integral abutment • Pile type: HP10x42 • 10’ prebore required • Pu = 92.3 kips per pile • Generalized Soil Category: Cohesive with Setup • Construction Control: WEAP

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Soil Profile at West Abutment

Ftg Bot Elev 933

Prebore Elev 923

10’ prebore

Final ground surface

Existing ground surface

11’

Surface Elev 937

30’

Soft Silty Clay

Silty Sand

Firm Glacial Clay

Very Firm Glacial Clay

4’

9’

10’

Layer Elev 917

Layer Elev 907

Layer Elev 926

Fill

N = 4

N = 6

N = 12

N = 20 35’

Boring Bot Elev 872

SPT N values are in units of blows per foot

2’

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County Problem 2 H30 - Integral Abutment - HP10x57

WEAP, Cohesive Soil, Downdrag, Bedrock H30-06 Pretensioned Prestressed Concrete Beam (PPCB) Bridge Standards (https://iowadot.gov/bridge/standards/english/h30-06.pdf)

• 30’ roadway width • 0° skew • 188’-10” long bridge • 3 Spans: 59.917’ – 69’ – 59.917’ (B59 and B67 beams) • Integral abutment • Pile type: HP10x57 • Use maximum of 15’ prebore (due to presence of downdrag) • Pu = 135 kips per pile • Generalized Soil Category: Cohesive (bedrock present) • Construction Control: WEAP

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Page 12: IDOT Pile Design Training Handout

Page 12 Standard Sheet H30-05-06

Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.2.6.1-1 for an HP10x57 is 243 kips

of nominal resistance. The factored resistance is (0.60)*(243 kips) = 145.8 kips which should be and, in fact, is greater than Pu = 135 kips.

Pu = 135 kips per pile

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Standard Sheet H30-01A-06, GENERAL NOTES

Note: The above statement is in conflict with the 2020 BDM update in BDM Article 6.1.6.1.1.1 which

requires 34 feet from the bottom of the footing to the top of the rock for an integral abutment with HP10x57 piles and 10 feet of prebore if no further analysis is performed (https://iowadot.gov/bridge/policy/06-01-00SubsLRFD.pdf). If prebore is increased to 15 feet then 37 feet from the bottom of the footing to the top of the rock is required. BDM Table 6.1.6.1.1.1-1 contains the full range of values for various conditions.

A reference to CADD note E177 is made in the plan notes above, but this note is no longer available in the BDM and is not required in the plan set.

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BDM Table 6.2.4.2-1. Prebored hole depths for abutments (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf)

BDM Table 6.2.4.2-2. Recommended H-pile penetration into bedrock (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf)

Rock classification Recommended penetration, feet

Broken limestone 8 - 12 where practical Shale or firm shale 8 – 12 Medium hard shale, hard shale, or siltstone with 50 ≤ N ≤ 200

4 – 8

Sandstone, siltstone, or shale with N ≥ 200

3

Solid limestone 1 – 3

BDM 6.2.4.6. Target Driving Resistance – Consider Setup? (https://iowadot.gov/bridge/policy/06-02-00PileLRFD.pdf) In the case of H-piles and cohesive soils with WEAP construction control the designer shall consider the benefit of setup in the determination of the target driving resistance except in the following cases:

• Piles driven to bedrock, • Piles subjected to downdrag, • Piles in contact with cohesive soil with an overall average N of less than 5, and • Piles used in accelerated bridge construction.

Even though the piles are steel H-piles, WEAP will be used for construction control, and the soil will be classified as cohesive the benefits of setup will not be considered for these piles since they are being driven to bedrock and downdrag is present.

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Soil Profile at West Abutment

Ftg Bot Elev 933

Prebore Elev 918

15’ prebore *

Final ground surface

Existing ground surface 7’

54’

Soft Silty Clay

Firm Silty Clay

Very Firm Glacial Clay

23’

15’

Layer Elev 888

Layer Elev 903

Surface Elev 926

Fill Assumed N = 20

N = 4

N = 12

N = 20 15’

Boring Bot Elev 872

SPT N values are in units of blows per foot

15’

Neutral Plane

Downdrag Zone

Bearing Zone

1’

Hard Shale, N = 162

Layer Elev 873

* Prebore was increased from 10’ to the maximum allowed of 15’ to reduce downdrag.

2’

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County Problem 3 H30 - Pile Bent - HP14x73

WEAP, Non-cohesive Soil, Scour H30-06 Pretensioned Prestressed Concrete Beam (PPCB) Bridge Standards (https://iowadot.gov/bridge/standards/english/h30-06.pdf)

• 30’ roadway width • 0° skew • 188’-10” long bridge • 3 Spans: 59.917’ – 69’ – 59.917’ (B59 and B67 beams) • Non-monolithic pile bent • Pile type: HP14x73 • 10’ scour • Pu = 168 kips per pile • Generalized Soil Category: Non-cohesive • Construction Control: WEAP

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Standard Sheet H30-47-06

Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.6.4.2.1.1 for an HP14x73 is 265 kips of nominal resistance. The factored resistance is (0.70)*(265 kips) = 185.5 kips which should be and, in fact, is greater than Pu = 168 kips.

Pu = 168 kips per pile

See P10L sheet on next page.

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page.

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Standard Sheet P10L

Note: The Structural Resistance Level 1 (SRL-1) limit from BDM Table 6.6.4.2.1.1 for an HP14x73 is (0.70)*(265 kips) = 185.5 kips. Additionally BDM Table 6.6.4.2.1.1 recommends a minimum height of the pile above the ground. For the HP14x73 this minimum height is 13’.

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Soil Profile at Pier 1

Cap Bot Elev 933

15’

Stream bed

1.5’

100’

Soft Silty Clay, N = 4

Fine Sand

Coarse Sand

7’

13’

Layer Elev 896

Layer Elev 913

Surface Elev 920

N = 13

N = 20 76’

Boring Bot Elev 820

SPT N values are in units of blows per foot

3’

Scour Zone

Bearing Zone

Pile encasement

4’ Layer Elev 909

Fine Sand, N = 2

9’

89’

Surface Elev 918 2’

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Appendix A. Friction and End Bearing Soil Charts End Bearing Soil Chart LRFD driven pile nominal unit geotechnical resistances for end bearing (BDM Table 6.2.7-1)

SOIL DESCRIPTION

BLOW COUNT ESTIMATED NOMINAL RESISTANCE VALUES FOR END BEARING PILE IN KIPS [KSI]

N60-VALUE (8) WOOD PILE (1),

(3)

STEEL “H” GRADE 50

PRESTRESSED CONCRETE (2)

STEEL PIPE (4)

MEAN RANGE 10 12 14 12 14 16 10 12 14 18 Granular material <15 --- (5) (5) (5) (5) (5) (5) (5) (5) (5) (5) (5)

Fine or medium sand

15 --- 32 (5) (5) (5) 60 84 108 32 48 64 108

Coarse sand 20 --- 44 (5) (5) (5) 84 116 148 44 64 88 144 Gravelly sand 21 --- 44 (5) (5) (5) 84 116 148 44 64 88 144 25 --- 56 (5) (5) (5) (7) (7) (7) (7) (7) (7) (7)

--- 25-50 (6) [ 2-4 ] [ 2-4 ] [ 2-4 ] (6), (7) (6), (7) (6), (7) (7) (7) (7) (7)

--- 50-100 (6) [ 4-8 ] [ 4-8 ] [ 4-8 ] (6) (6) (6) (7) (7) (7) (7)

--- 100-300 (6) [ 8-16 ] [ 8-16 ] [ 8-16 ] (6) (6) (6) (7) (7) (7) (7)

--- >300 (6) [ 18 ] [ 18 ] [ 18 ] (6) (6) (6) (7) (7) (7) (7)

Bedrock

--- 100-200 (6) [ 12 ] [ 12 ] [ 12 ] (6) (6) (6) (7) (7) (7) (7)

--- >200 (6) [ 18 ] [ 18 ] [ 18 ] (6) (6) (6) (7) (7) (7) (7)

Cohesive material

12 10-50 16 (5) (5) (5) 28 40 52 16 24 32 52 20 --- 24 [ 1 ] [ 1 ] [ 1 ] 44 64 84 28 36 52 84 25 --- 32 [ 2 ] [ 2 ] [ 2 ] 60 84 108 32 48 64 108 50 --- (6) [ 4 ] [ 4 ] [ 4 ] 116 (6) 164 (6) 212 (6) 56 96 128 212 100 --- (6) [ 7 ] [ 7 ] [ 7 ] (6) (6) (6) (6) (6) (6) (6)

Table notes: (1) Wood piles shall not be driven through soils with N > 25. (2) With prestressed concrete piles the preferred N for soil at the tip ranges from 25 to 35. Prestressed concrete piles have been proven to be difficult to drive

in very firm glacial clay and very firm sandy glacial clay. Prestressed concrete piles should not be driven in glacial clay with consistent N > 30 to 35. (3) End bearing resistance values for wood piles are based on a tip area of 72 in2. Values shall be adjusted for a different tip area. (4) Steel pipe piles should not be driven in soils with consistent N > 40. See the 1994 soils information chart [BDM 6.2.1.5] for end bearing when a conical

driving point is used. (5) Do not consider end bearing. (6) Use of end bearing is not recommended for timber piles when N > 25 or for prestressed concrete piles when N > 35 or for any condition identified with this

note. (7) End bearing resistance shall be 0.0389 x “N” value [ksi]. (8) Use uncorrected N-values until N60-values are available.

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Page 23 Friction Soil Chart LRFD driven pile nominal unit geotechnical resistances for friction bearing (BDM Table 6.2.7-2)

SOIL DESCRIPTION BLOW COUNT ESTIMATED NOMINAL RESISTANCE VALUES FOR FRICTION PILE IN KIPS/FOOT N60-VALUE (5) WOOD

PILE STEEL “H” GRADE 50

PRESTRESSED CONCRETE

STEEL PIPE

MEAN RANGE 10 12 14 12 14 16 10 12 14 18 Alluvium or Loess Very soft silty clay 1 0 - 1 0.8 0.4 0.8 0.8 0.8 0.8 0.8 0.4 0.4 0.4 0.8

Soft silty clay 3 2 - 4 1.2 0.8 1.2 1.2 0.8 0.8 0.8 0.8 0.8 0.8 1.2 Stiff silty clay 6 4 - 8 1.6 1.2 1.6 2.0 1.2 1.6 2.0 1.2 1.2 1.6 2.0 Firm silty clay 11 7 - 15 2.4 2.0 2.4 2.8 2.4 2.8 3.2 1.6 2.0 2.4 2.8

Stiff silt 6 3 - 7 1.6 1.2 1.6 1.6 1.6 1.6 1.6 1.2 1.2 1.6 1.6 Stiff sandy silt 6 4 - 8 1.6 1.2 1.6 1.6 1.6 1.6 1.6 1.2 1.2 1.6 1.6 Stiff sandy clay 6 4 - 8 1.6 1.2 1.6 2.0 2.0 2.0 2.4 1.2 1.6 1.6 2.0

Silty sand 8 3 - 13 1.2 1.2 1.2 1.6 1.6 1.6 1.6 0.8 0.8 1.2 1.6 Clayey sand 13 6 - 20 2.0 1.6 2.0 2.8 2.4 2.4 2.8 1.6 2.0 2.4 2.8

Fine sand 15 8 - 22 2.4 2.0 2.4 2.8 2.4 2.8 3.2 1.6 2.0 2.4 2.8 Coarse sand 20 12 - 28 3.2 2.8 3.2 3.6 3.2 3.6 4.0 2.0 2.4 2.8 3.6 Gravely sand 21 11 - 31 3.2 2.8 3.2 3.6 3.6 3.6 4.0 2.0 2.4 2.8 3.6

Granular material > 40 --- (2) 4.0 4.8 5.6 (2) (2) (2) (2) (2) (2) (2) Glacial Clay

Firm silty glacial clay 11 7 - 15 2.8 2.4 2.8 3.2 2.8 3.2 3.6 2.0 2.4 2.4 3.2 Firm clay (gumbotil) 12 9 - 15 2.8 2.4 2.8 3.2 2.8 3.2 3.6 2.0 2.4 2.4 3.2 Firm glacial clay(1) 11 7 - 15 2.4

[ 3.2 ] 2.8

[ 3.2 ] 3.2

[ 4.0 ] 3.6

[ 4.4 ] 3.2

[ 4.0 ] 3.6

[ 4.4 ] 4.0

[ 4.8 ] 2.0

[ 2.4 ] 2.4

[ 2.8 ] 2.8

[ 3.2 ] 3.6

[ 4.4 ] Firm sandy glacial

clay(1) 13 9 - 15 2.4

[ 3.2 ] 2.8

[ 3.2 ] 3.2

[ 4.0 ] 3.6

[ 4.4 ] 3.2

[ 4.0 ] 3.6

[ 4.4 ] 4.0

[ 4.8 ] 2.0

[ 2.4 ] 2.4

[ 2.8 ] 2.8

[ 3.2 ] 3.6

[ 4.4 ] Firm - very firm glacial

clay(1) 14 11 - 17 2.8

[ 3.6 ] 2.8

[ 4.0 ] 3.2

[ 4.8 ] 3.6

[ 5.6 ] 4.0

[ 4.8 ] 4.4

[ 5.2 ] 4.8

[ 5.6 ] 2.4

[ 3.2 ] 2.8

[ 3.6 ] 3.2

[ 4.0 ] 4.0

[ 5.2 ] Very firm glacial clay(1) 24 17 - 30 2.8

[ 3.6 ] 2.8

[ 4.0 ] 3.2

[ 4.8 ] 3.6

[ 5.6 ] 3.2 (3)

[4.8] 3.6 (3)

[5.6] 4.4 (3)

[6.4] 2.4

[ 3.2 ] 2.8

[ 3.6 ] 3.2

[ 4.0 ] 4.0

[ 5.2 ] Very firm sandy glacial

clay(1) 25 15 - 30 3.2

[ 4.0 ] 2.8

[ 4.0 ] 3.2

[ 4.8 ] 3.6

[ 5.6 ] 3.2 (3)

[4.8] 3.6 (3)

[5.6] 4.4 (3)

[6.4] 2.4

[ 3.2 ] 2.8

[ 3.6 ] 3.2

[ 4.0 ] 4.0

[ 5.2 ] Cohesive or glacial

material(1) > 35 --- (2) 2.8

[ 4.0 ] 3.2

[ 4.8 ] 3.6

[ 5.6 ] (2)

(2)

(2)

2.0 (4) [ 3.2 ]

2.4 (4) [ 4.0 ]

2.8 (4) [ 4.4 ]

3.6 (4) [ 5.6 ]

Table notes: (1) For double entries the upper value is for an embedded pile within 30 feet of the natural ground elevation, and the lower value [ ] is for pile depths more

than 30 feet below the natural ground elevation. (2) Do not consider use of this pile type for this soil condition, wood with N > 25, prestressed concrete with N > 35, or steel pipe with N > 40. (3) Prestressed concrete piles have proven to be difficult to drive in these soils. Prestressed piles should not be driven in glacial clay with consistent N >

30 to 35. (4) Steel pipe piles should not be driven in soils with consistent N > 40. (5) Use uncorrected N-values until N60-values are available.

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Appendix B. Soil Categories Geotechnical resistance factors for design (contract length) and for construction (target driving resistance) were statistically calibrated by Iowa State University researchers for three generalized soil categories based on a 70% rule. Therefore the designer will need to use these same categories when selecting geotechnical resistance factors for design:

• Cohesive: Along the pile length in contact with soil, 70% or more of the length is through soils classified as cohesive according to the table below.

• Mixed: Along the pile length in contact with soil, 31% to 69% of the length is through soils classified as cohesive according to the table below (or 31% to 69% of the length is through soils classified as non-cohesive according to the table below).

• Non-Cohesive: Along the pile length in contact with soil, 70% or more of the length is through soils classified as non-cohesive according to the table below.

Soil category based on soil classification (BDM Table 6.2.8)

Friction Pile Charts BDM Table 6.2.7-2

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Appendix C. Recommended Pile Penetration If an H-pile is designed with end bearing resistance in bedrock the pile contract length should include the penetration length as indicated in Table 6.2.4.2-2. Prestressed concrete and steel pipe piles should be driven to bedrock only with approval of the Soils Design Section. Timber piles shall not be driven to bear on bedrock.

Recommended H-pile penetration into bedrock (BDM Table 6.2.4.2-2) Rock classification Recommended

penetration, feet Broken limestone 8 - 12 where practical Shale or firm shale 8 – 12 Medium hard shale, hard shale, or siltstone with 50 ≤ N ≤ 200

4 – 8

Sandstone, siltstone, or shale with N ≥ 200

3

Solid limestone 1 – 3 The design penetration for any pile should be a minimum of 10 feet into hard cohesive or dense granular soil and a minimum of 20 feet into soft cohesive or loose granular soil. Piles driven through embankments should penetrate 10 feet into original ground unless refusal on bedrock or a competent layer occurs at a lesser elevation. (BDM 6.2.4.2)