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Grouted Rock Anchors

The Chance Grouted Rock Anchor is designed to be used in situations where the soil is too rocky to use screw anchors, but the rock is fractured preventing the use of wedge style rock anchors. The forged knob on the end of the anchor along with any extension couplings provides the interference fit with the grout. The holding capacity of the anchor is dependent on the bond stress between the rock and the grout. The Grouted Rock anchor is designed to be used inline with the guy. Failure to install within 5° of alignment with the guy load will significantly lower strength. Additional information about this anchor can be found on the Grouted Rock anchor installation instructions

To install a Grouted Rock Anchor requires first drill- ing a 6"-diameter hole. Then insert the anchor, assembled with any Round Rod Extensions and Guy Adapter needed. Portland-cement grout pumped in to completely fill the hole around the anchor takes approximately five days to cure.

ANSI C135.1 Galvanized per ASTM A-153

Grouted Rock Anchor - 1.23"-diameter rod
Cat. No. Length A Approx. Ship Wt. Each Std Pkg/Pallet
W104-0004 36" 17.6 lb. 1/40
W104-0055 84" 38.0 lb. 1/30

RR (Round Rod) Extension-1.25"-diameter rod
Cat. No. Length A Approx. Ship Wt. Each Std Pkg/Pallet
12696 42" 17.6 lb. 1/50
12697 60" 38.0 lb. 1/50
12698 84" 24.0 lb. 1/30
12699 120" 46.8 lb. 1/50
Click on Catalog Number to view sales drawing
Note: SS5 and SS150 extensions can be used in place of the RR extensions listed above.

Application Table for Cat. No. W104-0004 and W104-0055

  Ultimate Bond
Stress between
Rock & Grout psi
(see Notes 1, 2, 3)
Allowable Load
Capacity for
6" dia x 1' long grout column
lb/ft of length
(see Note 4)
Dolomitic Limestone
200 15000
Soft Limestone
Slates & Hard Shales
100 7500
Soft Shales 30 1800
Soil (see Note 18) 8 600
Class 5 8 600

  1. Ultimate bond stress values from the PTI (Post Tensioning Institute) and the grout to ground bond values from the FHWA (Federal Highway Administration) were used to arrive at the indicated ultimate bond stress between rock and grout used in the above chart.
  2. Identification of the rock and application of the chart values is the responsibility of those designing the rock anchor.
  3. The values in the chart are intended to provide conservative results.
  4. Higher bond stress values may be obtainable, but the associated investigation to determine appropriate values and the use of those values is left to those designing the rock anchor.
  5. The given ultimate stresses were applied over the surface of a 6" diameter x 1' long grout column, then divided by 3 to obtain the recommended allowed load per foot of length in the indicated rock or soil.
  6. Actual capacities will depend on the strength of the rock, the grout strength and the quality of the installation.
  7. A rough surface in the drilled hole is preferred as well as a clean hole free of loose material, soil, dust, etc.
  8. A 6" diameter hole is recommended for the use of the W104-0004 and W104-0055 rock anchors.
  9. The minimum bond length of the rock anchor to be engaging the rock is 5 feet.
  10. It is recommended that field testing be accomplished to confirm capacities.
  11. Anchor grout is to be made using Type I, II, III, or V Portland Cement conforming to ASTM C-150 specifications.
  12. The compressive strength of the grout shall be 3000 psi at the time of stressing.
  13. The grout should be flowable to reach the bottom of the drilled hole or pumpable if it is to be placed via a grout pump.
  14. The ultimate mechanical strength of the W104-0004 and W104-0055 rock anchors and associated extensions and terminations is 70,000 lbs when Chance/Hubbell anchor components are used.
  15. Water used in the grout mix should be potable (suitable for public consumption), clean and free of substances known to be harmful to portland cement or steel.
  16. It is recommended that grout be placed in the hole prior to inserting the rock anchor.
  17. When using pre-packaged grout mixes follow directions and use the water cement ratio recommended by manufacturer.
  18. For recommendations concerning bonded lengths and unbonded lengths, reference the PTI specifications.
  19. The rock anchor is to be installed in line with the guywire. Any misalignment is to be no more than ± 5 degrees.
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