Specifications

Overview

Axial displacement and axial force are applied through an actuator in the base of the cell. This cell is screw-driven from an integral base unit, housing the motor drive, which gives dynamic control of axial displacement or axial force. The cell is provided with a balanced ram to eliminate disturbance to constant cell pressure during dynamic tests. The cell fluid is water.

• Options of 10kN, 16kN, 20kN, 25kN, 40kN or 60kN maximum load.

• Dynamic control of axial displacement or axial force to 2Hz, 5Hz or 10 Hz maximum sinusoidal wave form.

• Performance specification conforming to the requirements of ASTM Designation D3999-91 "Standard Test Methods for the Determination of the Modulus and Damping Properties of Soils Using the Cyclic Triaxial Apparatus".

• Interchangeable load cells to accommodate very soft to very stiff soils with optional ranges of 1kN, 2kN, 4kN, 8kN, 10kN, 16kN, 25kN, 40kN and 60kN. One load cell appropriate to the maximum system capability is included.

• Optional local strain measurement and mid-plane pore pressure measurement.

• Precise control of low consolidation stresses using optional differential pressure transducer.

• Direct closed loop control of axial displacement, axial force, cell pressure, and back pressure.

• All tests defined using GDSLAB control and data acquisition software. On-line graphics and real time logging to hard disc. Data output is ASCII and compatible with Excel and other industry-standard spreadsheets.

• 38, 50, 70, 100, 150mm, 300mm diameter test specimens by interchangeable base pedestals and triaxial extension top caps (other sizes available on request).

• Simple access for transducers, valves and pipework via a 12 port (transducer) access ring. Plus 6 channels of 16 bit data acquisition

Test Menu by Module

• B CHECK

• ISOTROPIC/ANISOTROPIC CONSOLIDATION

• SATURATION RAMPS

• UNCONSOLIDATED-UNDRAINED

• CONSOLIDATED-UNDRAINED WITH PORE PRESSURE MEASUREMENT

• CONSOLIDATED-DRAINED WITH VOLUME CHANGE MEASUREMENT

• K-ZERO CONSOLIDATION AND SWELLING

• STRESS PATHS

• CYCLIC AXIAL LOADING TO 10Hz (cell pressure constant)

System Features

• Cyclic axial deformation control to 2Hz, 5Hz or 10 Hz maximum

• Cyclic axial force control to 2Hz, 5Hz or 10 Hz maximum.

• Quasi-static stress path control to set up datum of cyclic loading.

• Quasi-static B check and saturation ramps.

• Quasi-static classic axial compression and extension tests, stress controlled or strain controlled.

• Quasi-static stress path control, mixed drained and undrained.

• Quasi-static K-zero consolidation and swelling.

• Option for local measurement of axial and radial strain by Hall Effect transducers 38, 50, 70 and 100mm sized samples.

• Independent external measurement of axial deformation via axial motor shaft encoder.

• Optional internal submersible load cells for the measurement of axial load, 1kN, 2kN, 4kN, 8kN, 10kN, 16kN, 25kN, 32kN 40kN and 60kN.

• One synchronized, self calibrating PC-resident 16 bit data acquisition and control card.

• Pore pressure measured via transducer connected directly to the base pedestal.

• Optional mid-plane pore pressure probe.

• 12 port Transducer Access Ring.

• Optional test specimen preparation kits for 38, 50, 70 and 100mm diameter.

Specifications overview

• Test specimen diameters 38mm, 50mm, 70mm and 100mm (other sizes available on request up to 300mm).

• Axial load capacity options of 10kN, 16kN, 20kN, 25kN, 40kN or 60kN, cell pressure 2000kPa, axial displacement stroke +/- 100mm.

• Frequency response 2Hz, 5Hz or 10 Hz, sinusoidal waveform.

• Maximum double amplitude at maximum frequency is 4mm

• Resolution of measurement of axial displacement is 0.08µm.

• Accuracy of measurement of axial displacement is 70µm in 100mm i.e. 0.07%.

• Resolution of measurement and of axial force is better than 0.1% FRO.

• Accuracy of measurement of axial force is better than 0.1% FRO.

• Force feedback from internal submersible load cell.

• Pore pressure transducer 3.5MPa at base pedestal.

• Cell pressure control via 200cc/3MPa digital pressure/volume controller.

• Back pressure control via 200cc/3MPa digital pressure/volume controller.

• Option for dynamic cell pressure via 200cc/ 1MPa/1.4MPa Sig 3 Cell Pressure Controller.

• Option for Wet-wet differential pressure transducer and Remote Feedback Module for closed loop control of low consolidation stresses.

• Option for local axial strain by means of Hall Effect local strain transducers, +/- 3mm.

• Option for local radial strain measurement by means of Hall Effect local strain caliper, +/- 1.5mm.

• Option for local axial strain by means of LVDT local strain transducers, +/- 5mm.

• Option for local radial strain measurement by means of LVDT local strain caliper, +/- 5mm.

• P and S wave measurements with Bender Element System

• Option for local pore pressure measurement by mid-plane pore pressure probe, 1700kPa.

• Axial displacement and axial force independently controlled through closed loop system.

• Windows XP operating system or newer.

Specifications in detail

• The axial load/deformation control sub-system is screw-driven through the base of the cell. The built-in dynamic axial loading system is driven by a brushless dc servomotor. Manual or programmed computer control is via the GDS data acquisition and control card installed in the PC. This control can be initiated from the computer keyboard. The control card has internal digital function generators resident in firmware for sine wave control up to 10Hz. For closed loop load control, feedback is taken from the internal load cell output. For closed loop deformation control, feedback is taken from the axial motor high-speed shaft encoder. The axial load capacity has options of 10kN, 16kN, 20kN, 25kN, 40kN or 60kN. The axial displacement stroke is +/- 100mm.

• The radial pressure control sub-system is by one GDS digital pressure/volume controller, 200cc/3MPa, to give precise control of back pressure to 3kPa resolution. Manual control is via keypad and LCD display. Computer control is via the serial port at the back of your computer or via the USB port. If using an Advanced controller the interface could potentially be an integral IEEE-488 GP-IB computer interface, which requires an IEEE card on your PC. Functions include target pressure, target volume change, ramp/cycle pressure and ramp/cycle volume change.

• The cell is provided with a balanced ram. This compensates for the volumetric displacement of the loading ram into or out of the cell. Down the centre of the hollow ram, the cell fluid is hydraulically connected to a chamber through which the ram passes. In this chamber the ram has an annular piston attached to it. The annular area is exactly equal to the area of the ram. When the ram moves in the cell and causes a volume change, the annular piston causes an equal and opposite volume change. In this way the net volume change in the cell is zero. In addition, cell pressure acting on the annular ring automatically compensates for the effect of cell pressure acting on the ram. This means that the axial force capacity of the cell is independent of cell pressure.

• The back pressure control sub-system is by one GDS digital pressure/volume controller 200cc/3MPa to give precise control of back pressure to 3kPa resolution. Manual control is via keypad and LCD display. Computer control is via the serial port at the back of your computer or via the USB port. If using an Advanced controller the interface could potentially be an integral IEEE-488 GP-IB computer interface, which requires an IEEE card on your PC. Functions include target pressure, target volume change, ramp/cycle pressure and ramp/cycle volume change.

• The dynamic triaxial compression/extension cell can accommodate test specimens of diameter 38, 50, 70, and 100mm by interchangeable base pedestals and extension top caps. The cell is mounted on the integral base unit and provides access for axial load ram, cell pressure, back pressure and pore pressure through apertures in the base of the cell. The cell includes an internal axial load cell, a pore pressure transducer of capacity 3.5MPa, and a cell pressure transducer of capacity 3MPa.

• The Digital Control System (GDSDCS) has closed-loop feedback of displacement and load. With 16 bit data acquisition (A/D) and 16 bit control output (D/A), the GDSDCS runs at a control frequency of 16kHz per channel. This means that when running at 16Hz the system uses 1000 control points per cycle. When running at 1Hz, it uses 10000 control points per cycle. The advantage of the GDSDCS system is that, no matter which dynamic system is purchased, they all use the same high-speed control system. This ensures that the system has the highest level of functionality and reliability because all GDS dynamic systems, over the complete range, use the same high specification control system.

• The GDSLAB software package runs on a Windows XP operating system or newer. The software is modular and so can provide all of the conventional and advanced tests found in other GDS systems. The GDSLAB kernel provides on-line graphics with a comprehensive range of variables that can be selected for this display. Saved data may be analysed later by transfering the ascii text file directly to a spreadsheet. The built-in GDS data presentation facilities can also be used.

The system therefore gives extensive features for dynamic triaxial testing including:

Dynamic Test Module

• Dynamic cyclic loading tests at frequencies up to 10Hz. This module provides sinusoidal cyclic control of axial displacement or axial force. Plotting saved results gives cyclic stress paths based on average cross-sectional area i.e. the area of the volumetrically equivalent right cylinder. A complete cycle of data can be saved every N cycles where the value of N is defined by the user. A complete cycle of data is displayed every M cycles where the value of M is defined by the user.

Quasi-static triaxial testing including:

Saturation/Consolidation Module (SATCON)

• Isotropic consolidation, B check and saturation ramps.

Standard Triaxial Module

• Classic axial compression and extension strain controlled tests (the extension device is supplied as standard), drained and undrained.

Stress Path Module

• Generalised linear stress path control, mixed drained and undrained in either p, q or s, t control space. This facility can also be used to set the datum for dynamic tests.

Advanced Loading Module

• Independent control (constant, ramp, cycle) of:

• axial stress, axial strain or axial load

• radial stress

• back pressure

Can also be used for low frequency cyclic loading

K0 Consolidation and Swelling Module

• K0 consolidation and swelling under feedback control from either back volume or radial caliper feedback.

Permeability Module

• Flexible wall permeability (triaxial) with the following tests.

• Constant Head.

• Constant Rate of Flow.

• The computer set-up is as follows:

1 off Pentium PC, SVGA controller, 3.5" floppy, mouse, keyboard, Windows

1 off SVGA colour monitor

• The optional test specimen preparation kits comprise the following elements for 38, 50, 70 and 100mm diameter:

1 off three part split former

1 off split mould

1 off suction sleeve stretcher

10 membranes (packs of 10)

3 off o-rings (packs of 10)

10 off porous disc

2 off base disc

2 off top disc

• The complete basic system comprises the following separate and identifiable items as follows:

• 1 off triaxial cell and integral base unit housing the axial actuator

• 1 off 200cc/3MPa digital pressure/volume controller for control of cell pressure

• 1 off 200cc/3MPa digital pressure/volume controller for control of back pressure

• 1 off DCS data acquisition unit of86 channels of transducer input

• 1 off internal submersible load cell capacity as requested from choice of 1kN, 2kN, 4kN, 8kN, 16kN, 32kN, 40kN or 50kN. Additional optional load cells also available.

• 1 off 3.5 MPa pore pressure transducer

Optional Items

• Optional Hall Effect local strain transducers 38, 50, 70, 100mm (other sizes available on request)

• Optional LVDT local strain transducers 38, 50, 70, 100mm (other sizes available on request)

• Optional mid-plane pore pressure transducer 1700kPa

• Optional Bender Elements (P and S-wave)

• Optional upgrade to unsaturated soil testing i.e. HKUST wet-wet differential pressure measurements