![]() ![]() ) for the same 100 joints was estimated to within 1/2°. The mean value of the peak shear strength angle (arctanτ/σ Index tests and subsequent shear box tests on more than 100 joint samples have demonstrated thatφĬan be estimated to within ± 1° for any one of the eight rock types investigated. All these index values can be measured in the laboratory. The equation is based on three index parameters the joint roughness coefficientJRC, the joint wall compressive strengthJCS, and the residual friction angleφ The pump for vertical load is fitted with a pressure maintainer to assure uniform load during the test.Abstract: The paper describes an empirical law of friction for rock joints which can be used both for extrapolating and predicting shear strength data. NG-ShearBox/D is supplied complete with: 5 potentiometric transducers with 25mm travel (4 vertical and 1 horizontal) 2 mould formers 2 hand operated pumps for lateral and vertical load fitted with Bourdon gauges 2 pressure transducers for the direct acquisition of the load values on the external data logger (supply as accessory, see Multipurpose data logger for automatic data acquisition).The pump for vertical load is fitted with a pressure maintainer to assure uniform load during the test. NG-ShearBox/A is supplied complete with: 5 digital gauges 25x0.001 mm (4 vertical and 1 horizontal) 2 mould formers 2 hand operated pumps for lateral and vertical load fitted with Bourdon gauges.Main Features Two versions are available: ![]() ![]() The normal loading system is complete with an adjustable low friction pressure maintainer to absorb volume changes of the specimen during the shearing action and to ensure a constant vertical stress. The loads are recorded by Bourdon tube load gauges or by pressure transducers (in this case external data logger. The shear box consists of two halves, the upper being connected to two rams for reversible shearing action and the lower connected to a ram for normal load application. The apparatus consists of a shear box designed to accept samples not larger than 115x125 mm, or alternatively cores up to 102 mm dia. It is a simple and practical method of determining the strength and slope stability of rock, both in the field and in the laboratory. ![]() This apparatus was originally developed at Imperial College, London, by Professor E. ![]()
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