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Application of Tensioned Cable Bolts for Supplemental Support

Benjamin Mirabile

Technical Sales and Service Engineer

Jennmar Corporation of West Virginia

J. Rodney Poland

Regional Sales Manager

Jennmar Corporation of West Virginia

Alan Campoli, Ph.D.

Vice President

Jennmar Specialty, Inc

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Outline

•Overview of Tensioned Cable Bolts

•Laboratory Tests

•Case Study 1

•Case Study 2

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Non Tensioned Cable

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INSTáL Cable Bolts

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Post-Tensioned Cable

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Cable Tensioning Unit (CTU)

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Laboratory Tests

• Illustrate Constant Stiffness of Cable Material

• Evaluate Effect of Pre-Load on Total Deflection at Failure

• Effect of Development of Bearing Plate Contact

• Seating Effects of Barrel and Wedge Assembly

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Load-Deflection Tests

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Trendlines in Elastic Range

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Laboratory Test Conclusions

• Cable Material has Constant Stiffness in Elastic Range

• Pre-Load Decreases the Variability of the Load Response Curve in the Elastic Range

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Laboratory Results/Practical Application

• Reduction of Total Deflection Enhances Roof Stability

• Use of Cable Tensioning Unit Allows Immediate Development of Full Bearing Plate Contact with Roof—Especially Important in Broken Ground or Strata with Many Discontinuities

• Consistent Load Response

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Case Study 1

• Longwall Head Gate in Eagle Seam• 650-750 Feet Depth• Highly Laminated and Fractured

Sandstone with Mica Streaks• Primary Support—3/4” x 72” Torque

Tension with 2 Eq. Ft Grout• Supplemental Support--#8 Bar (1”)

Rigid Bar Truss

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Case Study 1

• T5 Channel with 4 Bolt Slots• Center Bolts—0.7” x 18’ Post-

Tensioned Cable• Outside Bolts—0.7” x 10’ Post

Tensioned Cable Angled Over Ribs

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Case Study 1

Installation and Site Conditions

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 1

Longwall Pass

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 1

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Case Study 2

• Longwall Recovery Face in Alma Seam

• 700 Feet Depth• Sandy Shale• Longwall Face “Parked” for 60 Days• Little or No Shield Leg Pressure• Shields Extended to Maximum Height

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Case Study 2

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Case Study 2

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Case Study 2

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Case Study 2

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Case Study 2

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Case Study 2

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Qualitative Effects of Pre-Tension

• Allows Designer to Select Starting Point on Load-Response Curve

• Allows Immediate Contact of Bearing Plate Against Mine Roof

• Empirical Data Suggests Superior Performance in Weak or Broken Ground as Compared to Non-Tensioned Cable Bolts

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Further Research

• Additional Laboratory Testing to Investigate Seating Effects of Wedges and Bearing Plate Contact

• Investigate Effects of Resin Grout on System Stiffness

• Underground Instrumentation Comparing Performance of Non-Tensioned and Tensioned Cable Supports

• Determination of Optimum Pre-Load

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Thank You

Questions?