Back Pressured Shear Box

Product Code : GDSBPS

The Back Pressure Shearbox (BPS) has the ability to perform direct shear tests with precise back pressure control, for the recreation and measurement of realistic slope failures.

 The BPS range includes a saturated version (control of pore water pressure), an unsaturated version (control of both pore water and pore air pressure) and a dynamic version.

Further Information:
Key features Benefits to the user
Internal loadcell: Internal loadcell for shear and optionally normal force for load measurements as close to the sample as possible for greater accuracy.
Rigid aluminium cell body: To reduce system compliance.
Unsaturated GDSBPS: The unsaturated GDSBPS is based on a standard, saturated device but modified to allow the measurement and control of matric suction (the difference between the pore air and water pressures).
Real-world situations to be modelled in the laboratory: All versions allow the pore pressures within the sample to be controlled. The control of pore pressure during direct shear testing allows real-world situations to be modelled in the laboratory.

L= 930mm x W = 420mm x H=1230mm

Displacement Accuracy

<0.1% FSO

Displacement Range

axial = +/- 15mm, shear = +/- 25mm

Load Range (kN)

25 normal and shear force


240V or 110V 50/60Hz single phase

Pressure Range (MPa)


Resolution of Measurement and Control

16 bit (± 25mm = ± 0.7μm(shear), ±10mm = ±0.3μm (axial)

Sample Sizes

60mm (Circular). 75x75 or 100x100mm (Square).

  • The GDSBPS apparatus can be specified with many different options, some are listed below but many more are available. Please contact GDS if the required specification is not listed here or if higher pressures / forces are required.
  • Upgrade to unsaturated back pressured shear box.
  • Maximum back pressure:
    • 1MPa basic.
    • Options to 10MPa.
  • Maximum axial and shear load:
    • 5kN basic.
    • Options to 100kN as part of standard range.
  • Normal (axial) load upgrade to electro-mechanical actuator.
  • Bender elements.