Development and Status of ACI Guide for Underground Shotcrete Specification

By

Harvey W. ParkerPast President, ITA

And

Chris BreedsPresident, SubTerra, Inc.

Shotcrete for AfricaCradle of Humankind, South Africa

March 2, 2009

Presentation Topics• Introduction & Background• Development of Concept & Scope• Timeline

– Organizational Developments– Interaction between ACI & ITA– Leadership Changes

• Concept & Overview of Guide– Tables– Photographs

Introduction & Background

• Very Long Gestation Period

Introduction & Background

• Early 1970’s-ACI 506 Started a ShotcreteReport/Manual

• 1990s-Restart by Harvey Parker & Rusty Morgan– Rusty Provided Example “Guideline Spec”

• For Shotcrete Repair of Hwy Bridges• Left Side = Spec Right Side = Guideline

• Abundant Discussion about Scope

Initial Organization

Main ACIShotcrete Committee

ACI 506

Other ACISubcomittees

ACI SubcommitteesOn

UndergroundShotcrete

Other ACI Subcommittees

ITA Stimulus

• ITA Working Group on Shotcrete– Formed in 1989

• ACI 506 Underground Shotcrete Subcommittee– Contributed to ITA as a Mirror Group

ITAMirror Working Groups

1. Work by NationalCommittee or

Working Group toAchieve National

Group Goals

2. Input from National GroupTo ITA Working Group

3. ITA Working GroupResults & Documents with

Feedback to each National Group

Concept• Original Concept: Considerable Design

– Design Aspect Abandoned-done by others• Didn’t water down the construction spec aspect

• User friendly text• Lots of photos to guide the spec writer through

the process• Give enough background information to

understand the issues and processes going on and to make the selection of what to include (or not include)

Introduction & Background• Discussion About Scope & Title

– Guideline Spec or Guide Spec– Guidelines or Guide for Spec

• Conflicting Opinions & Re-starts– Camel Factor

• Biggest Delays: – Making it shorter & succinct– Identifying & Finding the Right Photos

Leadership Changes

• ACI-506 - 6 Full Committee Chairs• ACI-506 Underground Shotcrete Chair

– Harvey Parker– Chris Breeds

• The Constant– Rusty Morgan

Tough Going but We are over the top

Guide for UndergroundShotcrete Specification

______________ACI 506.XR

Guide for Underground Shotcrete Specification

Reported by ACI Committee 506

Peter C. Tatnall* Lawrence J. Totten Dudley R. Morgan* Chair Vice-Chair Secretary Jon B. Ardahl Martin Gendreau Jeffrey Novak Raymond C. Schallom* Lars F. Balck Jill E. Glassgold Celik H. Ozyildirim Raymond J. Schutz Michael Ballou* Warren L. Harrison* Harvey W. Parker† Philip T. Seabrook Nemkumar Banthia Merlyn Isaak Ryan Poole W.L. Snow Chris D. Breeds† Marc Jolin* John H. Pye* Curtis White Patrick O. Bridger Kristian Loevile* James A. Ragland Peter T. Yen Wern-Ping Chen* Mark R. Lukkarila V. Ramakrishnan George Yoggy* Jean-François Dufour* Gregory McKinnon Michael Rispin* Christopher M. Zynda Steven H. Gebler __________ † Subcommittee Co-Chairs who produced this report. * Subcommittee members who produced this report. - Special acknowledgement is due Bill Edgerton, Janice Lindell, J. Denis O’Donnel, Sr., and Fred Sherrill for their contributions to this report. This document provides a guide for owners, contractors, designers, and testing, specifying and inspection organizations engaged in the application of shotcrete for underground support. The guide provides general information for the selection of constituent materials, and methods to proportion shotcrete. Typical methods of batching, mixing and handling of proportioned shotcrete materials are detailed along with shotcrete placement methods and equipment. Keywords: acceptance criteria; batching; inspection; methods of payment; mine and tunnel support systems; mixing and placement equipment; mixture proportioning; preconstruction and construction testing; quality assurance; quality control; safety; shotcrete; shotcrete application.

FOCUS and CONTENT

• Owners, Engineers, Specifiers, Inspectors, and Contractors

• Design, Planning and Implementation of Underground Shotcrete Programs

• 22 Chapters

Contents• Overview, Scope, Definitions• Submittals• Materials• Anchorage and Reinforcement• Materials Handling• Mixture Proportioning• Performance Requirements• QA/QC• Pre-construction Trials and

Testing• Construction Acceptance and

Inspection• Batching, Mixing and Supply• Placing Equipment

• Auxiliary Equipment• Safety• Preparation for Shotcrete and

Groundwater Control• Ground Reinforcement

Installation• Shotcrete Application• Curing and Protection• Shotcrete for Repair and

Rehabilitation of Structures• Measurement and Payment• References

Content of Each Section

• Brief Introduction

• An Example Specification with annotations

• A detailed commentary for each part of the Specification

• Photographs

Format

• Recommended specifications for submittals are provided in the Table.

• Guide Specification format: – left column provides the recommended

specification language – right column provides notes to the specifier.

Example Specification Commentary

4.1 Pre-construction submittals Submittals are usually required from construction contractors at least 28 days before the start of construction. This allows the appropriate project organizations time to review, and if required and accept the submittal.

4.1.1

Submit objective evidence that documents detail the qualifications of the work crew, including the supervisor, shotcrete nozzle operator(s) and shotcrete equipment operator(s).

Personnel qualifications and training results will be required at least 28 days before construction. Consider, as an additional submittal, the procedure for nozzleman training and certification. See ACI CP60.

Section 4 Submittals

Supporting Text

“These submittals serve as objective evidence and confirm that specific construction materials, installation methods, equipment, and trained or qualified personnel have met or exceeded the quality requirements identified in the project specifications and drawings.”

Section 6.0 Anchorage and ReinforcementExample Specification Commentary

6.1 Shotcrete anchor bolts or dowels Consider the provisions cited in ACI 318.

6.1.1

Shotcrete anchor bolts or dowels shall be made from ASTM A 615 grade 60 steel or equivalent as specified by the owner.

Steel grade may be 60 or 75.

6.1.2

Shotcrete anchor bolts or dowels shall be of the type, diameter, and length specified in the contract documents.

6.1.3

Provide shotcrete anchor bolts or dowels with attachment means to the shotcrete.

Means may be plate with nuts, hook ends, plates with reinforcing-bar spiders or welded studs.

6.1.4

Provide level pads for the anchor plates as specified in the contract documents.

6.1.5

Provide rockbolt and anchor bolt setting grout as specified in the contract documents.

Fig. 6.1a Rock bolting jumbo

Fig 6.1b Rock bolts and grout

Fig. 6.2 Tunnel with pattern bolting before shotcreting

Fig. 6.3 Wire mesh in tunnel with considerable overbreak

Shotcrete with Lattice Girders

• Size and Spacing

• Installation and Shotcrete Application

• Shotcrete Placement

Fig. 6.7a Close-up of a typical lattice girder

Fig. 6.7b Typical lattice girder during shooting (robotic)

Fig. 6.7c Typical lattice girder during shooting (manual)

Fig. 6.8 Tunnel with lattice girders

11.0 Pre-construction TrialsExample Specification Commentary

11.1. Materials qualification See Chapter 5, Materials.

11.1.1 Materials used in pre-construction testing shall be those that will be used for the work.

On large, important, or time-sensitive projects, consider selecting and applying shotcrete mixtures using alternative aggregate and cement and admixture sources. In the event that normal sources are disrupted, alternative materials that have been pre-qualified during pre-construction can be substituted. The potential disruption due to the lack of availability of these materials is therefore minimized.

11.1.2 Materials used in pre-construction testing shall be stored and handled as specified for the work.

See Chapter 7, Materials Handling and Storage.

Fig. 11.1 Shotcreting a panel

Fig. 11.2 Shotcreting a panel with a robotic nozzle

Fig. 11.3 Underground test panels

Fig. 11.4 Shotcreting overhead panels

16.0 SafetyExample Specification Commentary

16.1 The contractor shall prepare and submit a safety plan addressing all potential hazards to be encountered on the job site.

See discussion in Section 16.1, Underground safety.

16.2 The contractor shall supply personal safety equipment for all personnel involved withshotcrete, both underground and at the surface. Submittals shall be in accordance with specification 4.1.8.

See discussion in Section 16.2, Required personal safety equipment, and in 16.5, Non-personal safety equipment.

16.3 The contractor shall provide a well-lighted and ventilated work area for shotcrete application. Submittals shall be in accordance with specification 4.1.8.

See discussion in Section 16.3, View of the shotcrete work.

Fig. 16.1 Shotcrete nozzleman with personal safety equipment

Fig. 16.2 Shotcrete nozzleman with safety helmet

Fig. 16.3 A well-lighted tunnel heading

17.0 Preparation for ShotcreteExample Specification Commentary

17.1 Surface Preparation—Prepare surfaces to receive shotcrete as necessary to maximize bond strength giving proper consideration to the geological,geotechnical, andhydrogeological conditions.

Consideration must be paid to the overall design of the shotcrete support system as well as the more general aspects of surface preparation. Paragraph 17.1 provides some general guidelines in this area; however, this commentary is not intended as a “design guide.”

17.2 Drainage

17.2.1

Drainage materials used to control ground water inshotcreted areas shall be of the type specified in the contract documents.

17.2.2

Alternative means of ground water control may be submitted by the contractor for review and approval by the owner

Current Status

• Guide has been reviewed, rewritten and balloted, submitted to TAC

• TAC Comments have been incorporated and Balloted

• Final comments being incorporated and will soon be sent back to ACI for final processing

• Release Date not yet established

Thank You