BOR-EX Rod Type Borehole Extensometer
The BOR-EX is a rod-type multiple-point borehole extensometer (MPBX) from Roctest used to measure precise longitudinal displacement in rock, soil and concrete, for applications such as foundation settlement, tunnel subsidence, retaining-wall movement and underground-opening deformation.
- Range
- 25-200 mm (vibrating wire); 25-150 mm (potentiometer); 50 mm dial / 150 mm depth gauge
- Accuracy
- ±0.25% F.S. vibrating wire; ±0.5% F.S. potentiometer; ±0.003 mm depth gauge
- Resolution
- 0.02% F.S. vibrating wire; 0.01 mm potentiometer; 0.01 mm dial indicator
Overview
In detail
How it works
Anchors are set at specific depths in the borehole and connected to the instrument head by extension rods, typically run inside a protective sleeve so they can move freely while transmitting subsurface displacement. Technicians read the rod displacement against a reference plate at the head to calculate ground or soil movement.
Components
Two anchor types are available: groutable rebar anchors, preferred for downhole rock installations, and hydraulic Borros-type anchors, used in soil where deep prong penetration is needed; up to six anchors fit in a standard borehole. Extension rods come in fibreglass, for faster installation, or stainless steel, preferred for long extensometers, both supplied in sections for on-site assembly and run inside protective tubing to shield them from grout.
Reading options
Three head types are available: mechanical reading only (BOREX-M), electrical reading only (BOREX-E), and combined mechanical/electrical (BOREX-E/M). Reading methods and their typical performance are a dial indicator (50mm range, 0.01mm resolution), a depth gauge (150mm range, +/-0.003mm accuracy, 0.001-0.01mm resolution), a vibrating-wire transducer (25-200mm range, +/-0.25% F.S. accuracy, 0.02% F.S. resolution) and a potentiometer (25-150mm range, +/-0.5% F.S. accuracy, 0.01mm resolution). Electrical sensors operate from -20C to 80C; the LCD display operates from 0C to 40C.
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Specifications
Technical specifications
- Range
- 25-200 mm (vibrating wire); 25-150 mm (potentiometer); 50 mm dial / 150 mm depth gauge
- Accuracy
- ±0.25% F.S. vibrating wire; ±0.5% F.S. potentiometer; ±0.003 mm depth gauge
- Resolution
- 0.02% F.S. vibrating wire; 0.01 mm potentiometer; 0.01 mm dial indicator
- Operating temperature
- -20 to 80°C (electrical sensors); 0-40°C (LCD readout)
- Rod material
- Fibreglass (6.4 mm) or stainless steel (6.4 mm, 13.7 mm O.D. with tube)
- Anchor types
- Groutable rebar or hydraulic Borros-type
- Anchors per hole
- Up to 6
Related
Often specified alongside
ESS Earth
Resistance Wire Extensometer RWE
- Application
- Underground hard rock and coal mine displacement monitoring
- Monitoring points
- Pillars, stope walls, roof
Geosystems
JM Series Vibrating Wire Jointmeter
- Range
- 25, 50, 100, 150, 200, 250, 300 mm (200/250/300 mm not available for JM-E)
- Accuracy
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