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Geo-Drill Injection Anchor System

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The Williams Geo-Drill Injection Anchor System is today’s solution for a fast and efficient anchoring system into virtually any type of soil. The system has historically been known as a “self-drilling anchoring” because the hollow fully-threaded bar serves as both the drill string and the grouted anchor, thus installation is performed in a single operation. The sacrificial drill bit is threaded onto the end of the Geo-Drill bar and left in place following drilling. The drilling fluid (air, water, or grout) is introduced through the hollow bar and allows the spoils to flush from the borehole.
The Geo-Drill System is particularly suitable for soils that do not allow for open-hole drilling (i.e. granular soils that are collapsible in nature). In such cases, drilling with a grout fluid serves the purpose of flushing spoils from the borehole and prevents looser, surrounding material from collapsing due to the higher relative density of the grout. Williams Geo-Drill Injection Anchor System should be considered on any project requiring fast production that would otherwise need to involve a casing system in order to maintain borehole stability.

Geo-Drill Injection Anchor
Advantages of the Williams Geo-Drill Injection Anchor System
  • Fast, single-step anchoring system with simple equipment.
  • Eliminates the need for a cased borehole in collapsing soils.
  • Efficient installation since drilling and grouting can be performed in a single operation, saving both time and money.
  • Continuously drilling and grouting under high pressure causes the grout to permeate into looser soils and creates a bulb-effect for increased bond capacity.
  • Suitable for working in limited space and areas of difficult access.
  • Multiple ranges of drill bits suitable for most soil conditions.
  • Installed with standard track drill (top hammer) or hand-held drilling equipment, eliminating the need for larger casing rigs.
  • Continuously threaded bar pattern can be cut and coupled anywhere along its length.
  • Full stock of 10 foot long anchors, accessories and drill bits available in two different warehouse locations.
  • Corrosion protection systems available upon request.
  • FHWA approved for use as a micro pile.
  • Domestic material available upon special request.
B7X Geo-Drill Bar
Bar
Diameter
Minimum Net
Area Through
Threads
Minimum
Ultimate
Strength
Minimum
Yield
Strength
Nominal
Weight
Average
Inner
Diameter
Part
Number
32 mm
(1-1/4”)
0.556 in2
(359 mm
2)
58.4 kips
(260 kN)
47.2 kips
(210 kN)
2.1 lbs/ft
(3.1 Kg/M)
0.787”
(20.0 mm)
B7X1-32
32X mm
(1-1/4”)
0.776 in2
(501 mm
2)
81.5 kips
(363 kN)
66.0 kips
(294 kN)
2.7 lbs/ft
(4.0 Kg/M)
0.626”
(15.9 mm)
B7X1-32X
38 mm
(1-1/2")
1.067 in2
(688 mm
2)
112 kips
(498 kN)
90.7 kips
(404 kN)
3.76 lbs/ft
(5.6 Kg/M)
0.830”
(21.1 mm)
B7X1-38
51 mm
(2")
1.795 in2
(1158 mm
2)
188 kips
(837 kN)
152 kips
(677 kN)
6.26 lbs/ft
(9.3 Kg/M)
1.187”
(30.1 mm)
B7X1-51
76 mm
(3”)
3.880 in2
(2503 mm
2)
407 kips
(1811 kN)
329 kips
(1466 kN)
13.79 lbs/ft
(20.5 Kg/M)
1.890”
(48.0 mm)
B7X1-76
Threaded Bar Profile
The Injection Bar is a high strength-impact resistant heavy wall steel tubing conforming to ASTM A519 which is continuously threaded over it's 10' length with a heavy duty left hand thread/deformation pattern. The steel tubing provides maximum flow with minimum resistance during high pressure flushing and grouting operations. The thread form (similar for all diameters) is a unique Williams feature that provides a lower thread pitch angle to provide easier coupling disengagement without “locking up”, than conventional rope threads during drilling operations. This thread form provides more surface area and thread/deformations per unit length for superior bond capabilities over that of competitive drill steel thread forms. The bar's thread/deformation pattern has also shown to exceed the bond characteristics of ASTM A615 reinforcing steel. The lower thread angle allows the installed anchor to be torque-tensioned for fast tie back installations. The Geo-Drill Injection Anchor system is available with enhanced corrosion protection with hot-dip galvanized/epoxy coated bars and components. Installation adapters for the Geo-Drill Injection Anchors are available for all drill rigs.

Applications

Soil Nails
Soil Nails are non-tensioned, in-situ reinforcement for the stability of excavations and embankments in top-down construction. The Williams Geo-Drill Injection Anchor System is an ideal choice for soil nailing in difficult soils as it offers high installation rates. Hollow bar elements have gained approval for permanent soil nail use in Europe and have also been used extensively for permanent soil nails in the United States.

Prestressed Ground Anchors
Williams Geo-Drill Injection Bar Anchors can be used as a choice for pre-tensioned anchors in loose or collapsing soils without the need for a casing. A free length must be installed onto the anchor if the project specifications call for a pretension load to be applied from the bond length. Please consult with a Williams specialist for suggestions to properly attach a free length sleeve. Note to Designer: Consult with Williams for an appropriate level of corrosion protection if prestressed ground anchors are intended to be used for a permanent application.

Micro Piles
Williams Geo-Drill Injection Bar offer an excellent choice for micro piles in difficult ground conditions where open-hole drilling isn’t possible. The continuously threaded bar profile lends itself perfectly for restricted headroom applications because the bar can be cut and coupled at any length. The FHWA has approved hollow bar anchors for permanent use in micro pile applications.

Tunnel Spiles and Forepoling
The Geo-Drill Injection Anchor System are often used for spiling in NATM tunneling. Spiles are continuously drilled and grouted pre-support reinforcement to enable the heading of a tunnel to advance without the risk of falling debris. The anchors can also be used as face stabilization of portals.

Limitations of the System

In general, Williams recommends using the Geo-Drill Injection Anchor System in difficult soils that do not allow for open-hole drilling. Ground conditions featuring large voids or the presence of an artesian water condition are generally not suitable for a drilled and grouted hollow bar. In hard rock, conventional DTH (Down the Hole Hammers) in open-hole drilling offer a more efficient alternative. In all such cases, Williams offers solutions in their complete line of solid bar anchor systems and multi-strand tendon systems.
Williams Form Engineering Corp.
Geo-Drill
Information
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Geo-Drill
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