751.37 Drilled Shafts - Revision history

Hoskir: fixed math errors

2026-01-15T17:22:07Z

fixed math errors

Hoskir: /* 751.37.3 Design for Axial Loading at Strength Limit State */ fixing math errors

2026-01-15T17:16:58Z

751.37.3 Design for Axial Loading at Strength Limit State: fixing math errors

← Older revision		Revision as of 12:16, 15 January 2026
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	:''L<sub>i</sub>'' = length of shaft segment ''i'' (consistent units of length).		:''L<sub>i</sub>'' = length of shaft segment ''i'' (consistent units of length).

	<math>~~\boldsymbol~~ \phi_{qs-i}</math> and ''<math>\boldsymbol q_{s-i}</math>'' shall be determined in accordance with the provisions of this article, based on the material type present along the respective shaft segment.		<math>\phi_{qs-i}</math> and ''<math>\boldsymbol q_{s-i}</math>'' shall be determined in accordance with the provisions of this article, based on the material type present along the respective shaft segment.

	Side resistance shall generally be neglected or reduced, as recommended by the Geotechnical Section, over shaft segments with permanent casing and over any length of rock socket that is deemed unusable.		Side resistance shall generally be neglected or reduced, as recommended by the Geotechnical Section, over shaft segments with permanent casing and over any length of rock socket that is deemed unusable.

Hoskir: /* 751.37.3 Design for Axial Loading at Strength Limit State */ math errors

2026-01-15T17:15:32Z

751.37.3 Design for Axial Loading at Strength Limit State: math errors

Hoskir: /* 751.37.1.6 Drilled Shaft General Detail Considerations */ updated per RR3878

2024-05-23T20:40:01Z

751.37.1.6 Drilled Shaft General Detail Considerations: updated per RR3878

← Older revision		Revision as of 15:40, 23 May 2024
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	===751.37.1.6 Drilled Shaft General Detail Considerations===		===751.37.1.6 Drilled Shaft General Detail Considerations===
	[[image:751.37.1.6.~~jpg~~\|700px\|center]]		[[image:751.37.1.6 01.png\|700px\|center]]
	Pay items shown in above table are for example only, show actual pay items and quantities in plan details ~~as per~~ specific project.		Pay items shown in above table are for example only, show actual pay items and quantities in plan details for specific project.

	''Notes:''		''Notes:''
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	::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.		::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.
	::::See [[751.50 Standard Detailing Notes#G8. Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (starting at G8.1).		::::See [[751.50 Standard Detailing Notes#G8. Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (starting at G8.1).
	::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [~~[media~~:751.37.1.~~1 Design Aid 2021~~.~~pdf\|~~Design Aid: Minimum Rock Socket Length]].		::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [https://epg.modot.org/forms/general_files/BR/751.37.1.1_Drilled_Shaft_Design_Aid.docx Design Aid: Minimum Rock Socket Length].
			::(3) When difference between drilled shaft and column diameter is 6" a single reinforcement cage is typically used for the socket and shaft and the vertical reinforcement extends into the column. A separate column steel cage is then placed around the protruding shaft reinforcement without requiring an adjustment to minimum cover for rock socket or column reinforcement. When difference between drilled shaft and column diameter is 12” either the vertical column steel or dowels will need to be extended into the shaft or the cover in the socket and shaft will need to be increased to allow the shaft reinforcement to extend into the column. In the former scenario an optional construction joint is recommended as discussed in note 4 for oversized shafts. In the latter scenario the same number of vertical bars should be used in the shaft and column to allow the shaft bars to be tied to the column cage. Any reduction in cage diameter required for fit-up shall be considered in design.
			::(4) When difference between drilled shaft and column diameter is greater than 12" (oversized shaft generally 18" to 24" larger than column), show "Optional construction joint" at bottom of column/dowel reinforcement in the drilled shaft and use [[751.50_Standard_Detailing_Notes#G8._Drilled_Shaft\|EPG 751.50 Standard Detailing Notes G8.8 and G8.9]] in plan details.

	<center>		<center>
	{\| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center"		{\| border="1" class="wikitable" style="margin: 1em auto 1em auto" style="text-align:center"
	\|+		\|+
	\| style="background:#BEBEBE" width="400" \|'''[~~http~~://www.modot.org/~~business/consultant_resources/bridgestandards.htm~~ Bridge Standard Drawings]'''		\| style="background:#BEBEBE" width="400" \|'''[https://www.modot.org/bridge-standard-drawings Bridge Standard Drawings]'''</br> (Drilled Shafts - DSS → As Built Drilled Shaft Data [DSS_01])
	\|-		\|-
	\|align="center"\|[~~http~~://www.modot.org/~~business~~/~~standard_drawings2/drilled_shaft_new_title_block.htm~~ As Built Drilled Shaft Data ]		\|align="center"\|[https://www.modot.org/media/14725 As Built Drilled Shaft Data (PDF)]
	\|}		\|}

Hoskir: /* 751.37.1.1 Dimensions and Nomenclature */ updated per RR3878

2024-05-23T20:29:27Z

751.37.1.1 Dimensions and Nomenclature: updated per RR3878

← Older revision		Revision as of 15:29, 23 May 2024
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	\|colspan="5"\|<sup>'''4'''</sup> The dimensions “D<sub>s</sub>” and “L<sub>s</sub>” are not explicitly used in any of the design equations that follow in favor of generally referring to the diameter of any segment of an overall shaft as “D” which can be a rock socket segment. This is not entirely true for the dimension “L<sub>s</sub>” which is explicitly used as part of a settlement design equation that follows. Judicial use of the appropriate segment and use of the appropriate diameter and length of a segment is implicit to the correct use of the design equations that follow. (See [[#751.37.2 General Design Procedure and Limit States\|EPG 751.37.2 General Design Procedure and Limit States]].)		\|colspan="5"\|<sup>'''4'''</sup> The dimensions “D<sub>s</sub>” and “L<sub>s</sub>” are not explicitly used in any of the design equations that follow in favor of generally referring to the diameter of any segment of an overall shaft as “D” which can be a rock socket segment. This is not entirely true for the dimension “L<sub>s</sub>” which is explicitly used as part of a settlement design equation that follows. Judicial use of the appropriate segment and use of the appropriate diameter and length of a segment is implicit to the correct use of the design equations that follow. (See [[#751.37.2 General Design Procedure and Limit States\|EPG 751.37.2 General Design Procedure and Limit States]].)
	\|-		\|-
	\|colspan="5"\|<sup>'''5'''</sup> See [~~[media~~:751.37.1.~~1 Design Aid 2021~~.~~pdf\|~~Design Aid: Minimum Rock Socket Length]]		\| colspan="5" \| <sup>'''5'''</sup> See [https://epg.modot.org/forms/general_files/BR/751.37.1.1_Drilled_Shaft_Design_Aid.docx Design Aid: Minimum Rock Socket Length]
	\|}		\|}

Hoskir: /* 751.37.6.1 Reinforcement Design */ updated per RR 3680

2023-04-18T15:05:32Z

751.37.6.1 Reinforcement Design: updated per RR 3680

← Older revision		Revision as of 10:05, 18 April 2023
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	For minimum concrete cover for drilled shaft, see [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 701.4.12.1]. If drilled shaft diameter does not match Sec 701.4.12.1 then use concrete cover for the next greater diameter drilled shaft. For rock sockets use 3” min. clear cover.		For minimum concrete cover for drilled shaft, see [http://www.modot.org/business/standards_and_specs/SpecbookEPG.pdf#page=11 Sec 701.4.12.1]. If drilled shaft diameter does not match Sec 701.4.12.1 then use concrete cover for the next greater diameter drilled shaft. For rock sockets use 3” min. clear cover.

	For longitudinal reinforcement, splicing shall be in accordance with LRFD 5.11.5.		For longitudinal reinforcement, splicing shall be in accordance with LRFD 5.10.8.4.

	For transverse reinforcement, lap splices for closed circular stirrups/ties shall be provided and staggered in accordance with LRFD 5.10.6.3. Lap length of 1.3 '''l'''<sub>d</sub> (Class B) for closed stirrups/ties shall be provided in accordance with LRFD 5.11.2.~~6.4~~.		For transverse reinforcement, lap splices for closed circular stirrups/ties shall be provided and staggered in accordance with LRFD 5.10.4.3. Lap length of 1.3 '''l'''<sub>d</sub> (Class B) for closed stirrups/ties shall be provided in accordance with LRFD 5.10.8.2.6d.

	For lap length, see [[751.5 Structural Detailing Guidelines#751.5.9.2.8.1 Development and Lap Splice General\|EPG 751.5.9.2.8.1 Development and Lap Splice General]].		For lap length, see [[751.5 Structural Detailing Guidelines#751.5.9.2.8.1 Development and Lap Splice General\|EPG 751.5.9.2.8.1 Development and Lap Splice General]].

Smithk: /* 751.37.1.6 Drilled Shaft General Detail Considerations */

2021-11-02T17:53:44Z

751.37.1.6 Drilled Shaft General Detail Considerations

← Older revision		Revision as of 12:53, 2 November 2021
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	::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.		::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.
	::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.		::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.
	::::See [[751.50 Standard Detailing Notes#G8. Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (~~Starting~~ at G8.1).		::::See [[751.50 Standard Detailing Notes#G8. Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (starting at G8.1).
	::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]].		::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]].

Smithk: /* 751.37.1.6 Drilled Shaft General Detail Considerations */

2021-11-02T17:50:20Z

751.37.1.6 Drilled Shaft General Detail Considerations

← Older revision		Revision as of 12:50, 2 November 2021
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	::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.		::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.
	::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.		::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.
	::::See [[751.50 Standard Detailing Notes#G.8 Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (Starting at G8.1).		::::See [[751.50 Standard Detailing Notes#G8. Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (Starting at G8.1).
	::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]].		::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]].

Smithk: Per BR, clarified tip of casing elevation and min. rock socket length requirements in "Design Aid: Minimum Rock Socket Length".

2021-11-02T16:15:08Z

Per BR, clarified tip of casing elevation and min. rock socket length requirements in "Design Aid: Minimum Rock Socket Length".

← Older revision		Revision as of 11:15, 2 November 2021
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	\|colspan="5"\|<sup>'''4'''</sup> The dimensions “D<sub>s</sub>” and “L<sub>s</sub>” are not explicitly used in any of the design equations that follow in favor of generally referring to the diameter of any segment of an overall shaft as “D” which can be a rock socket segment. This is not entirely true for the dimension “L<sub>s</sub>” which is explicitly used as part of a settlement design equation that follows. Judicial use of the appropriate segment and use of the appropriate diameter and length of a segment is implicit to the correct use of the design equations that follow. (See [[#751.37.2 General Design Procedure and Limit States\|EPG 751.37.2 General Design Procedure and Limit States]].)		\|colspan="5"\|<sup>'''4'''</sup> The dimensions “D<sub>s</sub>” and “L<sub>s</sub>” are not explicitly used in any of the design equations that follow in favor of generally referring to the diameter of any segment of an overall shaft as “D” which can be a rock socket segment. This is not entirely true for the dimension “L<sub>s</sub>” which is explicitly used as part of a settlement design equation that follows. Judicial use of the appropriate segment and use of the appropriate diameter and length of a segment is implicit to the correct use of the design equations that follow. (See [[#751.37.2 General Design Procedure and Limit States\|EPG 751.37.2 General Design Procedure and Limit States]].)
	\|-		\|-
	\|colspan="5"\|<sup>'''5'''</sup> See [[media:751.37.1.1 Design Aid.pdf\|Design Aid: Minimum Rock Socket Length]]		\|colspan="5"\|<sup>'''5'''</sup> See [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]]
	\|}		\|}

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	::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.		::::See [[#751.37.1.3 Casing\|EPG 751.37.1.3]] for casing requirements and alternatives.
	::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.		::::When determining P bar diameter for barbill, assume 3/8” casing unless otherwise specified.
	::::See [[751.50 Standard Detailing Notes#Drilled ~~shafts~~\|EPG 751.50, E2]], for notes to include for drilled shafts and rock sockets (Starting at E2.29).		::::See [[751.50 Standard Detailing Notes#G.8 Drilled Shaft\|EPG 751.50, G8]], for notes to include for drilled shafts and rock sockets (Starting at G8.1).
	::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid.pdf\|Design Aid: Minimum Rock Socket Length]].		::(2) See [[#751.37.1.1 Dimensions and Nomenclature\|EPG 751.37.1.1 Dimensions and Nomenclature]] for [[media:751.37.1.1 Design Aid 2021.pdf\|Design Aid: Minimum Rock Socket Length]].

	<center>		<center>

Smithk: /* Commentary on EPG 751.37.1 General */

2021-06-29T13:10:23Z

Commentary on EPG 751.37.1 General

← Older revision		Revision as of 08:10, 29 June 2021
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	The four classes of operational importance include:		The four classes of operational importance include:
	:* Minor or low volume route.		:* Minor or low volume route
	:* Major route.		:* Major route
	:* Major bridge costing less than $100 million.		:* Major bridge costing less than $100 million
	:* Major bridge costing greater than $100 million.		:* Major bridge costing greater than $100 million.

← Older revision		Revision as of 12:15, 15 January 2026
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	:''R<sub>pR</sub>'' = factored tip resistance (consistent units of force) and		:''R<sub>pR</sub>'' = factored tip resistance (consistent units of force) and

	:<math>~~\boldsymbol~~\gamma Q</math> = factored load for the appropriate strength limit state (consistent units of force).		:<math>\gamma Q</math> = factored load for the appropriate strength limit state (consistent units of force).

	Tip resistance and side resistance shall be computed according to the provisions of EPG 751.37.3 for the material type(s) encountered. The Structural Project Manager or Structural Liaison Engineer shall be consulted before utilizing design methods other than those provided in EPG 751.37.3 for calculating the geotechnical resistance of drilled shafts.		Tip resistance and side resistance shall be computed according to the provisions of EPG 751.37.3 for the material type(s) encountered. The Structural Project Manager or Structural Liaison Engineer shall be consulted before utilizing design methods other than those provided in EPG 751.37.3 for calculating the geotechnical resistance of drilled shafts.
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	:<math>A_{s-i} = \pi \cdot D_{i} \cdot L_{i}</math> = perimeter interface area for shaft segment ''i'' (consistent units of area),		:<math>A_{s-i} = \pi \cdot D_{i} \cdot L_{i}</math> = perimeter interface area for shaft segment ''i'' (consistent units of area),

	:<math>~~\boldsymbol~~ \phi_{qs-i}</math> = resistance factor for unit side resistance along shaft segment ''i'' (dimensionless),		:<math>\phi_{qs-i}</math> = resistance factor for unit side resistance along shaft segment ''i'' (dimensionless),

	:''<math>~~\boldsymbol~~ q_{s-i}</math>'' = nominal unit side resistance along shaft segment ''i'' (consistent units of stress),		:''<math>q_{s-i}</math>'' = nominal unit side resistance along shaft segment ''i'' (consistent units of stress),

	:''D<sub>i</sub>'' = shaft diameter for shaft segment ''i'' (consistent units of length), and		:''D<sub>i</sub>'' = shaft diameter for shaft segment ''i'' (consistent units of length), and
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	:<math>A_p = \pi \cdot \frac{D^2}{4}</math> = cross-sectional area of the shaft at the tip (consistent units of area),		:<math>A_p = \pi \cdot \frac{D^2}{4}</math> = cross-sectional area of the shaft at the tip (consistent units of area),

	:<math>~~\boldsymbol~~ \phi_{qp}</math> = resistance factor for unit tip resistance (dimensionless),		:<math>\phi_{qp}</math> = resistance factor for unit tip resistance (dimensionless),

	:''<math>~~\boldsymbol~~ q_p </math>''= nominal unit tip resistance (consistent units of stress), and		:''<math>q_p </math>''= nominal unit tip resistance (consistent units of stress), and

	:''D'' = shaft diameter at the tip of the shaft (consistent units of length).		:''D'' = shaft diameter at the tip of the shaft (consistent units of length).

	<math>~~\boldsymbol~~ \phi_{qp}</math> and ''<math>\boldsymbol q_p</math>'' shall be determined in accordance with the provisions of this article, based on the material type present within a depth of ''2D'' below the tip of the shaft.		<math>\phi_{qp}</math> and ''<math>\boldsymbol q_p</math>'' shall be determined in accordance with the provisions of this article, based on the material type present within a depth of ''2D'' below the tip of the shaft.

	Tip resistance shall be neglected, as recommended by the Geotechnical Section, when the shaft tip is located within karstic rock or other conditions where tip resistance cannot be reliably determined.		Tip resistance shall be neglected, as recommended by the Geotechnical Section, when the shaft tip is located within karstic rock or other conditions where tip resistance cannot be reliably determined.