Extensometers • Anchors • Readout Instruments • Sensors
 

 

Model A-1 Single Point Mechanical
The Model A-1 Single Position Rod Extensometer is a very simple, rugged and reliable instrument, easily installed and completely recessed within the borehole for optimum protection. The Model A-1 is a natural first choice for monitoring the safety in and around tunnels and mine openings.
Specifications  
Standard Range up to 100 mm
Least Reading 0.025 mm
Borehole Diameter 35, 44, 51, 64 mm
Maximum Length 10 m
 

Model A-3 Multiple Point Groutable Anchor
The Model A-3 Multiple Point Rod Extensometer is the preferred design for installation in downward directed boreholes which are easily filled with cement grout. Up to eight anchors can be installed, at various depths, in a 76mm (3in.) dia. borehole providing the capability to locate multiple failure plains and zones of movement.
Specifications  
Standard Range up to 300 mm nominal
Least Reading 0.025 mm
Borehole Diameter 76 mm or over
Maximum Length 100 m
 

Model A-4 Multiple Point Snap-Ring Anchor
The Model A-4 Multiple Point Rod Extensometer with Snap-Ring Anchors is quickly and easily installed in boreholes in hard or competent rock. Anchors are pushed to the required depth on the end of setting rods and then a cord is pulled to remove the locking pin which allows two retaining rings on each anchor to snap outward and grip the borehole. Up to eight anchors can be installed, at various depths, in a 76mm (3in.) dia. borehole. Particularly useful in upward directed boreholes.
Specifications  
Standard Range up to 300 mm nominal
Least Reading 0.025 mm
Borehole Diameter¹ 38 mm to 76 mm
Maximum Length 50 m
¹Any borehole diameter up to 3 inches may be specified. Note that the size of the hole required increases with the addition of more measuring points
 

Model A-5 Multiple Point Hydraulic Anchor
The Model A-5 Multiple Point Rod Extensometer with Hydraulic Anchors is recommended for use in soft ground and soils or in rock where the borehole may deteriorate. This anchor is very versatile and can be used in boreholes of varying diameter and roughness oriented in any direction.
Specifications  
Standard Range up to 300 mm nominal
Least Reading 0.025 mm
Borehole Diameter¹ 38 to 102 mm
Maximum Length 100 m
¹Note that the size of the hole required increases with the addition of more measuring points
Photo of A-6  

Model A-6 Rod Type Extensometer
The Model A-6 Rod-Type Extensometer uses continuous lengths of fiberglass rods (inside protective tubing), cut to customer-specified lengths, coiled at the factory and shipped ready for installation. The extensometer is lightweight, making it easier to handle for installation and less costly to ship. On-site assembly time is minimal and the installation procedure is simplified.

Specifications  
Standard Range up to 300 mm nominal
Least Reading 0.025 mm
Borehole Diameter¹ 50 mm minimum (for single point)
Maximum Length 100 m
¹Note that the size of the hole required increases with the addition of more measuring points
Photo of A-9  

Model A-9 Retrievable Extensometer
The Model A-9 Retrievable Extensometer* is designed to measure deformations in boreholes in rock, concrete, and other construction materials. The device can be used in pile load test studies, plate jacking tests and virtually any application where a hole can be drilled or a pipe can be cast into the structure being studied. The system features adjustable gage lengths, rapid and simple installation/removal and high accuracy using a variety of transducers including Vibrating Wire and DCDT’s. Adapters for use in square tubing are also available.
*Patent No. 5,585,555

Specifications  
Standard Range¹ 6, 12, 25 mm
Sensitivity 0.02% F.S.
Accuracy ±0.1% F.S.
Temperature Range² –20°C to +80°C
Diameter

45 mm (Anchor)
25 mm (Transducer)

Overall Length 495 mm
¹Other ranges available on request ²Other temperature ranges available on request
Photo of Anchor Types  

Extensometer Anchor Types
1. Borros Type Hydraulic Anchor – For use in soft soils and clays, especially in augered boreholes. Can also be driven directly through soft ground without a borehole being required.

2. Groutable Anchor – The preferred anchor for use in downward-directed boreholes. The preassembled extensometer is installed in the borehole and is then filled with cement grout. These anchors can also be used in upward-directed boreholes with a more complicated grouting procedure.

3. Hydraulic Anchor – For use in rough boreholes in rock and soft ground, especially if dilations and contractions of the borehole are anticipated. Also useful in upward directed boreholes with or without grouting.

4. Snap-Ring Anchor – For use in hard or competent rock where smooth uniform boreholes can be drilled. The simplicity of its design allows for quick and easy installation.
Photo of Anchor Types  

Readout Instruments • Sensors
1. Model 1400-4 Digital Depth Micrometer – Readout of borehole extensometers is made on a digital counter after manual adjustment of the thimble. Accuracy is 0.01 mm, Range is 25 mm extensible to 150 mm using the extension rods supplied.

2. Model 1400-1 Dial Indicator – Used for quick and easy readout of borehole extensometers. Accuracy is 0.01 mm, Standard Range is 50 mm.

3. Model 1500 Linear Potentiometer – Utilizes a sturdy 6.5 mm diameter rod which protrudes from both ends as the actuating shaft. This facilitates connection of the linear potentiometer to extenso-meter rods and also permits a mechanical check on the readings.

4. Model 4450 VW Displacement Transducer – The Model 4450 Vibrating Wire Displacement Transducer provides remote readout for Geokon Extensometers. They are particularly useful where other types of VW sensors are used and where long cable runs are required.
Photo of 1610  

Model 1610 Tape Extensometer
The Model 1610 Tape Extensometer is designed to measure small changes in the distance between opposite walls or between the roof and floor of excavations, tunnels, or mine openings. It can also be used to monitor deformation in structures and supports and to measure movements of unstable slopes. Readout is provided electronically via a front panel LCD.

Specifications  
Tape Lengths 15, 20, 30 m and 50, 66, 100 ft
Accuracy ±0.01 mm
Tension on Tape 10 kg
Overall Length 550 mm
Photo of 1900  

Model 1900 Magnetic Extensometer
The Model 1900 Magnetic Extensometer is designed to measure settlement or heave of soft ground under the influence of loading or unloading due to the construction of embankments, fills, buildings, foundations, and structures. A probe is lowered inside a telescoping guide tube to detect and measure the position of magnetic anchors located around the guide tube at various depths along the borehole or within the fill. Plate anchors are used in fill and “spider” anchors in boreholes.

Specifications  
Standard Range unlimited (cable lengths 30, 150 m)
Sensitivity ±1 mm
Repeatability ±3 mm
Temperature Range –30°C to +80°C
Borehole Size 102 to 152 mm