Rock Shear Box Apparatus
Standards
Description
This apparatus was originally developed at Imperial College, London, by Professor E. Hoek. It is a simple and practical method of determining the strength and slope stability of rock, both in the field and in the laboratory, and it is the equipment behind the direct shear test on rock discontinuities described in ASTM D5607.
The shear box accepts samples no larger than 4.5 × 4.9″ (115 × 125 mm), or cores up to 4″ (102 mm) diameter. It is built in two halves: the upper half is connected to two rams that give a reversible shearing action, and the lower half to a ram that applies the normal load. Loads are read from Bourdon tube gauges, or taken from pressure transducers into an external data logger.
The normal loading system carries an adjustable low friction pressure maintainer. It absorbs the volume change of the specimen while shearing is under way, which is what keeps the vertical stress constant through the test rather than letting it drift as the specimen dilates. Read more in our rock mechanics blog.
Gauge Range50 kN
Core DiameterØ4″ (102 mm)
Versions2
Weight99 lbs (45 kg)
NG-ShearBox Versions
Two versions are available. They run the same test on the same frame, and differ in how the readings are taken: by eye from digital gauges, or electrically into a logger.
NG-ShearBox/A
Supplied with five digital gauges, 25 × 0.001 mm, four vertical and one horizontal; two mould formers; two hand operated pumps for lateral and vertical load, fitted with Bourdon gauges. The vertical load pump carries a pressure maintainer to hold the load uniform through the test.
NG-ShearBox/D
Supplied with five potentiometric transducers with 25 mm travel, four vertical and one horizontal; two mould formers; two hand operated pumps for lateral and vertical load with Bourdon gauges; and two pressure transducers that take the load values directly into an external data logger, supplied as an accessory. The vertical load pump carries the same pressure maintainer.
The /D version is the one to choose when the test has to produce a recorded curve rather than a set of readings written down by the operator; the multipurpose data logger for automatic data acquisition is ordered with it.
NG-ShearBox Technical Specifications
The frame is small enough to be carried to a site, which is the point of the design: the same box is used in the field and on the bench.
| Specification | NG-ShearBox |
|---|---|
| Gauges range | 50 kN × 1 kN |
| Maximum sample size | 4.5 × 4.9″ (115 × 125 mm), or cores up to Ø4″ (Ø102 mm) |
| Overall dimensions, frame only | 18.1 × 9.8 × 23.6″ (46 × 25 × 60 cm) |
| Approximate weight | 99 lbs (45 kg) |
Where the strength of the intact rock is wanted rather than the strength of a joint, the point load tester gives an index in the field with almost no specimen preparation.
Have Questions or Need to Confirm a Detail?
Tell us whether you read the test by gauge or log it, and the size of the samples you shear, and we will confirm which version fits and what the logger has to handle. Send a quick request online with those two details.
For Laboratories
Need Additional Quality Control Equipment to Build Your Laboratory?
Rock shear testing is only one part of a complete quality control laboratory. NextGen can help you equip your entire lab with coring machines, core cutters and grinders, point load testers, shear box apparatus, abrasivity testers, and other supporting solutions, all coordinated as one complete project.
- One partner to equip your complete laboratory
- Installation, training, calibration
- Support for the life of the equipment
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