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Ground Anchor Systems
Concrete Anchor Systems
Post Tensioning Systems
Threaded Bars with Fasteners
Tie Rods & Tie Backs
Micro Piles
Concrete Forming Hardware Systems
Williams products are made in the USA

Final Considerations

Rock & Soil
Anchors
Case
Histories
Corrosion
Protection
Clearances:
  • Allow sufficient drill hole diameter clearance for PVC sleeves, centralizers, grout tubes, etc., as well as the required bond zone grout diameter.
  • Bolt placement design should allow sufficient clearance from confining edges, pockets, or structures to allow room for installation drills, tools, and tensioning components.

Exposed End Protection:
  • End caps filled with grout should be used for bolts under permanent anchor lock off loads. End caps filled with corrosion inhibiting grease should be used only for bolts that are temporary, or whose loads will be monitored and/or re-stressed.

Anchorage plates:
  • Anchor plates should be designed as close to perpendicular to the bolt axis as possible. This may require raised grout pads or chipping out the rock surface with percussion tools. In the case of newly cast in place concrete, a special recessed pocket (later filled with concrete) or an angled projection can be formed. Plates on steel walers or sheet pile may require special angled bearing supports or wedge plates from a steel fabricator.
  • Spherical or bevel washers should be used only as a means to take up any residual angle that is left from the gross angle adjustment methods mentioned above.
  • In the case of pre-stressed bolts the hydraulic jack frame must usually bear directly on the bearing plate and perpendicular with the bolt axis.
  • Plate sizes should be designed around the project load requirements as well as, the bearing surface strength, the drill hole diameter, and any placement restrictions. No manufacturer has a standard plate for all conditions.
Anchor Bars:
  • Actual (major) diameters of some threaded bars may be larger than the advertised "nominal size". Additional clearances may be necessary in bearing surfaces and ducts. Fully threaded high tensile bars should not be subjected to field bending, welding, used as ground for welding, or cut with (acetylene torch) high heat sources.
Cement Grouts:
  • Normal grouts for rock bolting require maximum ability to flow into rock seams and cracks and should no contain sand or aggregates.
  • Neat cement grouts should be high strength, non corrosive, and non-shrink.
  • Cold weather conditions can retard grout curing times.
  • The more water added to the mix, the weaker the grout.
  • Site conditions may require consolidation grouting to assure grout return for rock bolts installed in highly fractured rock.
Resin Grouts:
  • Anchors must use advertised drill hole diameters with appropriate cartridge diameters in order to be effective. Larger drill holes can cause inadequate mixing, shrinkage, and reduction in bond length.
  • Anchorage lengths shown in resin manufacturers data are considered as being an ideal length and should be only used as an initial guide for site trials to establish actual bond requirements.
  • Wet hole conditions may reduce resin bond values by 30% or more.
  • Some shales or other rocks with high clay mineral content may not be suitable for resin anchoring.
General Problems in Rock Bolting:
  • Inadequate subsurface investigation and geologically engineered designs that do not address the load requirement / rock quality interaction.
  • Drill holes that are not clean, straight, of the correct diameter, not at the correct depth, and are not free of running water.
  • Collapsing drill holes may require casing, or the use of Williams self drilling anchors.
Williams Form Engineering Corp.
Rock & Soil
Anchors
Case
Histories
Corrosion
Protection
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