Rock Shear Box Apparatus

Standards

• ASTM D5607

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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.

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.

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.

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.