Single Point Mechanical Rod Extensometers

Model A-1

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.

Multiple Point Rod Extensometers, Groutable Anchor

Model A-3

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 76 mm diameter borehole providing the capability to locate multiple failure planes and zones of movement.

Multiple Point Rod Extensometers, Snap-Ring Anchor

Model A-4

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 76 mm diameter borehole. Particularly useful in upward directed boreholes.

Multiple Point Rod Extensometers, Hydraulic Anchor

Model A-5

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.

Flexible Rod Extensometers

Model A-6

The Model A-6 Flexible Rod 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.

Retrievable Extensometers

Model A-9

The Model A-9 Retrievable Extensometer (Patent No. 5,585,555) 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.

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 (please see the Model 1950 data sheet).

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.

Settlement Points (Borros Type)

Model 1950

The purpose of the heave/settlement points is to measure vertical movements in foundation soils during and subsequent to construction. The heave / settlement point consists of a three-prong anchor, a ¼" standard inner pipe, and a 1" standard outer pipe. The pipes are assembled in sections and fastened together with standard couplings to the required anchor depths.

Readout Instruments and 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.

Tape Extensometers

Model 1610

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.

Magnetic Extensometers

Model 1900

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.