List of major instruments

GDS_LF_GNS_Santanu Misra_1

Stiff Load Frame (40 tonne)

Global Digital Systems (GDS) load frame with controlled rate of either displacement or stress in compression and tension. Used for measurement of tensile, unconfined compressive, and triaxial strength, particularly for ‘soft rocks’.

Forney_LG_GNS_Santanu Misra_1

Hydraulic Load Frame (100 tonne)

Forney hydraulic load frame with uniform rate of displacement for use in compression. Used for measurement of unconfined and triaxial strength, particularly for ‘hard’ rocks.

WF_LoadFrame_Santanu Miara

Mechanical Load Frame (5 tonne)

Wykeham Farrance (WF) mechanical load frame with uniform rate of displacement for use in compression. Used for measurement of triaxial strength of soils where needed.

Triaxial cells and other controllers used with the load frames include:

  • Geotechnical Consulting and Testing Systems (GCTS) cell for use in the GDS frame at confining pressures up to 32 MPa. Includes measurement of pore pressure and/or volume change along with axial and radial strain on NX (54 mm) and HQ (62 mm) diameter specimens.
  • GNS Science cell for use in GDS frame at confining pressures up to 8 MPa. Includes measurement of pore pressure and/or volume change along with axial strain on NX and HQ size specimens.
  • WF cells for use in the WF frame at confining pressures up to 1.7 MPa. Includes measurement of pore pressure and/or volume change along with axial strain on 38 mm, 50 mm and 60 mm diameter specimens.
  • Hoek cells for use primarily in Forney frame at confining pressures up to 50 MPa. Axial strain measured with testing in primarily in undrained conditions in individual cells for either EX (22 mm diameter), NX or HQ size specimens.
  • GDS pressure / volume controllers provide cell pressure and back pressure for testing in the GNS Science and GCTS triaxial cells under drained or undrained conditions.
  • For unconfined compression testing, which is performed in either the GDS stiff loading or the Forney load frames, axial and circumferential strain can be measured by techniques that includes, linear displacement transducers (DCDT or LVDT), calipers, chains or strain gauges.
  • For tensile testing, which is mainly performed in the GDS frame, jigs are used in the measurement of either indirect and direct tensile strengths
DBPSB_GNS_Santanu Misra

Dynamic Back Pressure Shear Box

Shearbox developed by Durham University and GDS for use under conventional direct shear, with control of back pressure, or under dynamic oscillation. Under conventional direct shear loading both the vertical (normal) and horizontal (shear) loads may be applied under displacement or stress control. Control of the back pressure inside the shear box allows loading changes in an actual slope to be mimicked and pore pressures measured for the evaluation of shear surface development. Dynamic loading in either the vertical or horizontal direction, at up to 5 Hz, may be applied under displacement or stress control. Specimens, either intact or remoulded, are typically 20 mm thick and 100 mm square. For further information on this leading edge equipment, click here.

Direct_ShearBox_GNS_Santanu Misra

Direct Shear box

WF direct shear box with application of horizontal load under displacement control.The shear box may be used for peak or residual strength on either intact or remoulded material. Specimens are typically 20 mm thick and either 60 mm square, 60 mm in diameter or 100 mm square. Rates of shearing are geared between 0.00048 and 1.2 mm/min with an ability to automatically reverse in direction after a set amount of travel.

Rong_Shear_GNS_Santanu Misra

Ring Shear apparatus

Controls ring shear apparatus with application of horizontal load under angular displacement.The shear box is used for residual strength on remoulded material, in particular silts and clays. Specimens have annular ring shape with diameters of 70 (internal) and 100 (external) mm, with a typical thickness of 5 mm. Rates of shearing are infinitely variable between 0.001 to 199 °/min.

Consolidation_Santanu Misra

Consolidation frames

WF and GNS Science frames with lever arms for application of load. The WF frame has a 10:1 lever ratio for a maximum pressure of 6 MPa on a 75 mm diameter specimen. The GNS Science(Hiload) frame has a 40:1 lever arm ratio for a maximum pressure of 60 MPa on a 75 mm diameter specimen. Specimen diameters up to 240 mm may be tested in the Hiload frame. A hydraulic (Rowe) cell for 75 mm diameter specimens is also available.

Air_Permeability_GNS_Santanu Misra

Air Permeability cell

EX Hoek cell fitted with drainage end caps for air flow. Air flow rates through oven dried specimens are measured at varying confining pressures.

Vp Vs_ Santanu Misra

Sonic velocity measurement

Olympus pulse generator with P and S wave crystals mounted in GCTS platens. Specimens placed between platens with measurement of waveforms to determine travel times for calculation of velocities (Vp or Vs).