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GDS Instruments Triaxial Testing Product Catalogue 2014

World leaders in the manufacture of laboratory systems for soil & rock

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About GDS Instruments

GDS Instruments (Geotechnical Digital Systems, or simply GDS) designs, develops and manufactures material testing machines and software used for the computer-controlled testing of soils and rocks. This technology is used to evaluate the mechanical properties that are key in geotechnical and earthquake engineering design.

Since being founded in 1979, it is estimated that GDS products have been used to help achieve over 1000 PhD’s. As well as being the first choice for academic research, GDS products have been used in many world renowned commercial laboratories for projects including the Three Gorges Dam in China, the Millau Viaduct in France, the Vasco da Gama Bridge in Portugal, Terminal Five at Heathrow and the new Crossrail link in London.

GDS employs over 35 permanent members of staff at their offices in Hook, Hampshire, UK, as well as working with a network of agents spanning 40 countries. GDS UK based staff include 3 PhD’s, 8 qualified civil / geotechnical engineers, 4 software designers, 4 hardware designers and 5 electrical/electronics specialists, allowing GDS the capability to design, build, test and ship their products directly to the customer.

In 2011 GDS were awarded the prestigious Queens Award for “Enterprise in International Trade”.

Values at GDS

GDS believes in providing the best equipment for the job combined with first class support from engineers who understand the equipment and applications. GDS design and develop all their products in-house using their team of geotechnical engineers, software designers, hardware designers (3D CAD) and electrical/electronics designers and specialists. This allows GDS to have complete control of the design, build, test and shipping process. GDS’ in-house expertise allows the capability to design bespoke systems (hardware, electronics and software), which forms a significant part of GDS’ reputation.

GDSLAB software supports every GDS computer controlled device manufactured since 1979, as well as devices from other manufacturers that have long since been made obsolete by them. This forms part of our unique commitment to long term customer support.

When you receive training from or ask a technical question of GDS, your reply will be from, or via a geotechnical engineer. This is our philosophy for ensuring the best service possible. Great service = repeat customers and we have many repeat customers.

GDS production and manufacturing is carried out in the UK to strict quality standards and our management systems are ISO9001 accredited.

GDS Customers

GDS work closely with Research and Commercial companies. Utilising our network of agents has allowed GDS to work in many countries around the world and become involved with some world renowned organisations / institutes on a variety of different projects.

Please Note: Due to continued developments, specifications of products within this brochure may change.


www.gdsinstruments.com

Introduction to GDS Triaxial Testing ApparatusGDS are world leaders in Static, Dynamic and Unsaturated triaxial testing systems. In addition to complete systems, GDS also supply individual components such as pressure controllers, specialist transducers, unsaturated soil testing upgrades and bespoke units supplied to customer’s specifications.

Static Triaxial Testing Systems:The GDSTAS (Triaxial Automated System) is a load frame based system where the axial loading is applied by a load frame. This is one of the most configurable systems in the GDS range. By choosing the load frame, the pressure controller capacity and the triaxial cell capacity, the system can be configured for soft soils right up to a high pressure rock testing system. The lower capacity is generally the system of choice for commercial laboratories, with the upper range system the choice for rock mechanics laboratories. Based on all the same features of the GDSTAS, the high pressure environmental triaxial automated system (HPETAS), can be fitted with a heating or cooling system that is PC controlled.

The GDSTTS (Triaxial Testing System) is the original automated stress path system created by GDS using a Bishop and Wesley hydraulically actuated cell. Axial stress is applied directly as a stress through a bellofram diaphragm, i.e. is a true stress controlled system. The system can be configured using Enterprise, Standard or Advanced controllers.

UNSAT (Unsaturated Testing) represents the GDS range of upgrades for performing unsaturated testing. GDS offer four types of unsaturated testing, Method A, B, C and D.

GDSVIS (Virtual Infinite Stiffness) is the premier high capacity load frame in the GDS range. The VIS is a unique GDS development, as well as being a very stiff design of load frame, it allows the axial loading system to operate as though it has infinite stiffness (zero system compliance). Dynamic Triaxial Testing Systems:The ELDYN (Enterprise Level Dynamic System), is the lowest cost GDS dynamic triaxial testing system. Generally considered to be far superior to pneumatically actuated systems, this electro-mechanically actuated system is designed to compete with low cost pneumatic systems directly on price, whilst being superior on performance. This is the system of choice for teaching establishments and commercial testing.

The DYNTTS (Dynamic Triaxial Testing System), is the top level device in the GDS dynamic triaxial system range. This advanced dynamic system contains the most flexibility in configuration and a no-compromise approach in terms of accuracy, stability and features. The system of choice for advanced commercial testing and research.

GDSHLF (Hydraulic Load Frame), contains a dynamic actuator built into the cross beam of the frame. Load capacities are up to 250kN and +/- 50mm stroke capability based around a stiff loading frame. The LDCTTS, is a dynamic cyclic triaxial testing system based on the GDSHLF, using large diameter triaxial cells to enable tests to be performed on large particle sizes such as ballast.

The True Triaxial Apparatus (GDSTTA), has a defining characteristic that, unlike conventional triaxial apparatus, all three principal stresses can be controlled independently, rather than just two in a conventional triaxial system. This allows a wider range of complex stress paths to be performed.

GDSTTS system in a commercial laboratory.

GDSTTA sample preparation.



Triaxial Automated System (GDSTAS)

Key Features: Benefits to the User:Each system may be configured exactly to the customer’s specification and budget:

The user can choose the load frame, pressure controllers, triaxial cell or just parts to integrate into existing equipment to build their ideal TAS set-up to match budget to requirement.

Automated software control:The software directly controls the cell & back pressure, testing rate, in addition to managing all data acquisition. Automated control allows tests to proceed continuously and increases the throughput of tests.

Interchangeable range of load cells: Enables the user to run tests on soils of different stiffness and match the load transducers accordingly, giving greater accuracy of results.

Submersible load cells are standard: Seal friction does not effect load readings.

Standard set-ups available (ELTAS, STDTAS, ADVTAS, HPTAS):

GDS has a range of standard GDSTAS set-ups to help the user identify the correct set-up. The set-ups based on the pressure the systems will run to. See technical specifications below for system information.

Compatible with other manufacturers products:

If a user has existing components they may incorporate them with GDS equipment to create a system, saving capital expenditure.

Technical Specification:

Load Range (kN):

Enterprise (ELTAS): 50, 100,Standard (STDTAS): 50, 100, 250, 500 Advanced (ADVTAS): 50, 100, 250, 500, 1000High Pressure (HPTAS): 50, 100, 250, 400, 500, 1000, 2000

Pressure Range (MPa):

Enterprise (ELTAS): 1Standard (STDTAS): 1 to 4Advanced (ADVTAS): 2 to 8High Pressure (HPTAS): 8 to 128

Sample Sizes (mm): 20 to 300

Tests that can be Performed:B-check saturation, unconsolidated undrained (UU) triaxial, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests and stress paths. Please Note - The availability of tests may depend on selected hardware/software.

Upgrade Options:Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain, laser sample measurement, very low effective stress testing and unsaturated testing.

Overview: The GDS Triaxial Automated System (GDSTAS) is a load frame-based triaxial testing system. The system is configured by choosing from a range of load frames, triaxial cells, pressure controllers and software. The system can be configured as a multi-station commercial testing apparatus right through to high load rock testing at research level. If an existing system requires upgrading, parts of the GDSTAS system can be incorporated with existing equipment (including those from some other manufacturers) to upgrade the system.

Standards:

ASTM D-4767 ASTM D-5034


Overview: The GDS Triaxial Testing System (GDSTTS) is a fully automated triaxial testing system designed principally for stress path testing. The GDSTTS is based on the classic Bishop & Wesley type stress path triaxial cell which controls stress directly on the sample. The system can be configured using Enterprise, Standard or Advanced level controllers (depending on the required accuracy / maximum pressure). The 38/50mm cell can provide up to 7kN axial force, with the larger 70/100mm cell up to 25kN. This is the system of choice for teaching laboratories and research institutes.

Standards:

Triaxial Testing System (GDSTTS)


Key Features: Benefits to the User:Each system may be configured exactly to the customer’s specification and budget:

Users can choose the transducers, pressure controllers, triaxial cell or just parts to integrate into existing equipment to build their ideal set-up.

Direct actuation of axial stress through the hydraulically controlled ram in the base of each cell:

The Bishop and Wesley cell is designed specifically for stress path testing. Direct axial stress application means greater accuracy for stress control.

GDSTTS can run advanced tests: Tests such as stress paths, slow cyclic and K0, all under PC control.Standard through to advanced configurations:

GDS provide advanced (ADVTTS) systems with all the features of the standard systems but with higher accuracies and resolution.

May be upgraded at any time: Additional transducers, software modules, bender element testing andunsaturated testing makes the system future proof.


Accuracy of Pressure Measurement: Standard (STDTTS) <0.15% full range, Advanced (ADVTTS) <0.1% full range

Accuracy of Volume Measurement: Standard (STDTTS) 0.25% measured value , Advanced (ADVTTS) <0.1% measured value

Load Range (kN): Standard (STDTTS): 7 or 25 , Advanced (ADVTTS): 7 or 25, High Pressure (HPTTS): 7 or 25

Pressure Range (MPa): Standard (STDTTS): 1,2,3,4. Advanced (ADVTTS): 1,2,3,4. High Pressure (HPTTS): Up to 10

Resolution of Pressure Measurement: Standard (STDTTS): 1kPa, Advanced (ADVTTS): 0.1kPa

Resolution of Volume Measurement: Standard (STDTTS): 1mm3, Advanced (ADVTTS): 0.1mm3

Sample Sizes (mm): 38/50 or 70/100, upgrades available up to 150

Tests that can be Performed:B-check saturation, unconsolidated undrained (UU) triaxial, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests and stress paths. Please Note - The availability of tests may depend on selected hardware/software.

Upgrade Options:Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain and unsaturated testing. A high pressure STDTTS is available for cell pressure up to 10MPa.




Key Features: Benefits to the User:Choice of different methods: To suit your testing requirements and budget, see options A, B, C & D below.

Hong Kong University of Science and Technology:

Method B has been developed in conjunction with HKUST (Hong Kong University of Science and Technology), who are specialists in unsaturated soil testing.

Mixed and matched: Methods may be ‘mixed and matched’ to create a custom system.

GDS experience:

GDS has knowledge of many different unsaturated test methods and can objectively advise customers on the best method for their test requirements. GDS are not limited to a single solution and have currently over 100 unsaturated systems in use.

Triaxial Unsaturated Testing Methods:• Method A: Direct volume change measurement of pore air and water using a GDS pore air pressure/volume controller,

water pressure controller and measurement of atmospheric pressure.• Method B: HKUST inner cell - Total specimen volume change is measured from the change in water level in an inner

cell using a differential pressure transducer.• Method C: Double walled cell - A GDS pressure volume controller is used to measure inner cell volume change which

is directly related to sample volume change. Due to the outer cell pressurisation, the inner cell wall is considered to be infinitely stiff.

• Method D: On-sample local strain transducers measure directly on sample to calculate total volume change.


Method A: Resolution of measurement: Accuracy of measurement:

Pressure = 0.2kPa, volume = 1mm3

Pressure = <0.1% full range, volume = 0.25%

Method B:

Resolution of volume change measurement:Accuracy of sample volume change measurement:

<10mm3

Estimated at 32mm3 or 0.04% volumetric strain for a triaxial specimen 38mm in diameter, 76mm in height

Method C:

Resolution of measurement of cell volume:Accuracy of measurement of cell volume:

1mm3

0.25%

Method D: Resolution of displacement: Accuracy:

<0.1μmHall Effect = 0.8% FRO, LVDT = 0.1% FRO

Overview: GDS Unsaturated Triaxial Testing System (UNSAT) is an extension to traditional triaxial testing, in that soils from above the water table may be tested under conditions approaching the in-situ stress state and degree of saturation. All GDS triaxial testing systems (as well as triaxial equipment from other manufacturers*) can be modified to allow for unsaturated triaxial testing. GDS provide 4 methods to perform unsaturated testing.

Unsaturated testing can also be added to the following test types, Shear, Hollow Cylinder, Resonant Column, Consolidation and True Triaxial Testing.

*Please confirm existing equipment with GDS to check for compatibility.

Unsaturated Testing of Soil (UNSAT)



Tests that can be Performed: B-check, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests, stress paths and unconsolidated undrained (UU) triaxial.

Typical Applications:High Pressure / Load triaxial testing and unconfined testing.

Overview: The GDS Virtual Infinite Stiffness loading system (GDSVIS) is the premier load frame in the GDS range. The VIS allows the axial loading system to operate as though it has infinite stiffness (zero system compliance). This type of frame is unique to GDS. The VIS functionality is achieved by calibration and correction of system compliance.

The GDSVIS is extremely stiff and designed principally for rock testing to allow minimum backlash at the point of sample shearing (other, less stiff load frames do not give analagous results at this critical point in the test due to the recovery of the load frame under fast unload conditions).

Virtual Infinite Stiffness Loading System (GDSVIS)


Computer Interface: USBDimensions: Nominal Size: 2.3m x 1.0m x 0.96mDisplacement Accuracy: 0.05% of full rangeDisplacement Range (mm): 100Load Range (kN): 100, 250, 400, 500

Power: 92-265v, A.C. 48-440Hz, 65w maximum, single phase three wire earthed supply, 2A fuse x 2

Weight Approx (kg): 800 to 2000 (depending on model)Resolution of measurement and control: 100kN = 3N, 250kN = 8N, 400kN = 12N, 500kN = 15N

Key Features: Benefits to the User:

Load-deformation relationship:The GDSVIS is calibrated to provide precise data on the load-deformation relationship of the entire load application and load measuring system, which is then automatically used for self compensation.

Built in feedback:All VIS frames have feedback control and continuous display of axial load and platen displacement to allow simple and confident control of force and displacement.

Automatic correction: VIS provides automatic correction for system compliance, a common cause of error, which can under-estimate results of sample stiffness.

Column strength: The 500kN load frame has been built with 4 columns for extra strength and rigidity and can hold a cell size with a 700mm outer cell diameter.



Key Features: Benefits to the User:Pressure ranges: Large range of pressures available up to 100MPa.

Range of specimen size: Large range of standard sample sizes. Custom sample sizes are available upon request 20mm - 500mm diameters.

Optional balanced ram: Accurate testing with a Balanced Ram, see full description below.Low pressure cell construction: Aluminium with perspex wall making it light weight and easy to handle.High pressure cell construction: Stainless steel for long life with no corrosion.

GDS have been designing and making triaxial cells for over 30 years. GDS have learnt not to compromise on materials or surface treatments. As a result GDS manufactures all cells in the UK from top specification Aluminium Alloys and state of the art surface treatment to give our users equipment that lasts.

What are the advantages of a Balanced Ram?A balanced ram system compensates for the up thrust on the ram exerted by the cell pressure. GDS’ system utilises a secondary chamber around the ram that balances the pressure in the cell against a second piston seal such that the pressure load is not exerted onto the loadframe. This system means that a smaller range loadframe can be used to achieve the same deviator loadings on the sample. For example, if a cell has a 50mm diameter ram and a cell pressure of 32MPa this would give an upthrust of over 63kN that would have to be deducted from the maximum achievable deviator loading that a given frame can apply. With a balanced ram, the full load frame capacity may be used to apply axial force on the sample as there is zero ram upthrust. In addition, a balanced ram within a high pressure passive cell eliminates disturbance to constant cell pressure during axial loading.

Upgrade Options:Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain, unsaturated testing, transducer access rings and temperature control.

Max Sample Size (mm) and Pressure Range (MPa):

Low Pressure (<5MPa) Cells: 50mm/1.7MPa, 70mm/2MPa, 76mm/3.4MPa, 100mm/1.7MPa, 100mm/2MPa, 150mm/1.7MPa, 200mm/1MPa, 250mm/1MPa, 300mm/1MPa

High Pressure (>5MPa) Cells with Balanced Ram: 54mm/64MPa, 100mm/64MPa

High Pressure (>5MPa) Cells without Balanced ram: 50mm/14MPa, 50mm/64MPa, 70mm/100MPa, 10mm/14MPa, 10mm/20MPa

Hydraulically Actuated Cells: 50mm/2MPa, 100mm/2MPa, 50mm/10MPa

Overview: GDS produce an extensive range of triaxial cells in order to satisfy the complex range of tests required by today’s modern geotechnical laboratories. In addition, there are a number of features such as balanced ram, access ports and access rings for internal transducers that are offered. In summary, the cells are grouped in the following categories:-

Traditional Passive Triaxial Cells• Low Pressure (< 5MPa).• High Pressure (> 5MPa with balanced ram).• High Pressure (> 5MPa without balanced ram)

Active Triaxial Cells (Hydraulically Actuated Triaxial).

Triaxial Cells (CELLS)




Heating only system (Ambient to 60oc, optionally to 100oc):

The heating system works using thermal pads attached to the outside of the cell then enclosed within an environmental chamber to retain the heat. There are up to 4 temperature sensors relaying back to the control box for enhanced temperature accuracy.

Combined Cooling / Heating System (-20 to 60oc):

The cooling system uses a coiled tube section inside the cell, this is connected through the standard ports within the cell base to a glycol cooling unit, therefore temperature transfer is close to the specimen.

PC controlled: Temperature control is added to selected GDSLAB test modules to allow temperatures to be easily set for each configured test stage.

Gaseous back pressures: Can be adapted for gaseous back pressures such as Air, CO2 or Nitrogen.

Flexible system set-upThe HPETAS is made up of several apparatus each of which have a number of options that can be tailored to suit specification and budget. The pressure & samples you will be testing determines the options available.

Tests that can be Performed:B-check, consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial), constant rate of loading (CRL), constant rate of strain (CRS), slow cyclic testing, K0 (K-Zero), multi-stage testing, quasi-static (low speed/creep) tests, stress paths and unconsolidated undrained (UU) triaxial.

Upgrade Options:Bender elements, unsaturated testing, local strain transducers and gaseous back pressures.


Load Range (kN): 50, 100, 250, 400, 500, 1000, 2000Pressure Range (MPa): 8, 14, 16, 20, 32, 64, 100Sample Sizes (mm): 38 to 150Available Temperature Ranges: -20°C to 60°C / ambient to 100°C / -20°C to 100°C

Overview: The High Pressure Environmental Triaxial System (HPETAS) can be fitted with a heating or cooling system that is automatically controlled alongside the whole system via software.

Based on the same features as the GDSTAS system, the main difference with the HPETAS system is the triaxial cell and the optional temperature control system. Two options are available, one allows heating only and the other can heat and cool the cell. All of the same features apply for this system as for GDSTAS (stress paths, slow cyclic loading etc).

High Pressure Environmental Triaxial System (HPETAS)




Electro-mechanical system:

The ELDYN system supersedes systems using pneumatic actuators in terms of life costs and overall usable performance. Electro-mechanical systems can carry out full load dynamic testing to the stated frequency. Pneumatic systems tend to reduce the available amplitude with load due to the amount of air that needs to be moved from one side of the actuator to the other.

Cost savings, environmental benefits and safer operation:

Electro-mechanical systems are more environmentally friendly as they only draw the energy required to do the test, resulting in lower life costs. Electro-mechanical systems are also safer to run due to no high pressure air or hydraulic pipelines being required. No large noisy power packs are required to be running all the time, the ELDYN only requires a standard mains electricity outlet, this reduces the laboratory space required and the installation costs.

Tests that can be Performed:Consolidated drained (CD), consolidated undrained (CU), consolidation (Triaxial) dynamic, cyclic loading of samples under either load or strain, slow cyclic testing, quasi-static (low speed/creep) tests, stress paths and user defined waveforms.

Upgrade Options:Optional upgrade to user defined waveforms, upgrades from 5kN to 10kN, Bender element system (Vertical, Horizontal, S and P waves), hall effect local strain, LVDT local strain and unsaturated testing.


Actuators: Highly accurate dynamic electro-mechanical actuatorAxial Displacement Encoder: YesAxial Load: +/- 5 kN at 5Hz (upgradeable to +/-10kN)Computer Interface: USBData Acquisition: 16 BitLoad Range (kN): 5 (optional 10)Operating Frequency (Hz): 5 (optional 10)Pressure Range (MPa): Depends on cell chosen (2 standard)Sample Sizes (mm): Depends on cell chosen (38 to 150 standard)

Overview: The GDS Enterprise Level Dynamic Triaxial Testing System (ELDYN) is a triaxial system, based on an axially-stiff load frame with a beam mounted electro-mechanical actuator. The ELDYN has been designed to fulfil the demand within the geotechnical laboratory testing industry for a lower cost, more basic dynamic triaxial testing system, yet still performs to the very advanced standards that customers expect from GDS.

Standards:

Enterprise Level Dynamic Triaxial Testing System (ELDYN)




Advanced Dynamic Triaxial Testing System (DYNTTS)

Key Features: Benefits to the User:High accuracy electro-mechanical control:

The DYNTTS system is capable of very small strain static tests through to large strain dynamic tests.

Interchangeable load cells: Allows user to accommodate very soft to very stiff soils with ranges of 1, 2, 4, 8, 10, 16, 25, 40 and 60kN.

In-built balanced ram (up to 5Hz systems):

Keeps cell pressure constant during cycling, meaning a dynamic pressure controller is not required (unless dynamic cycling of cell pressure is required).

Interchangeable pedestals and triaxial extension top caps:

Allows testing of 38, 50, 70 and 100mm diameter test specimens in the same cell.

Direct closed loop of axial displacement & axial force: Accurate control in either axial displacement or axial force mode.


Actuators: High accuracy electro-mechanicalAxial Force Accuracy: <0.1%Axial Force Resolution: 16bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell)Axial Load (kN): 10, 25, 40 or 60Displacement Range (mm): 100Displacement Resolution: 0.20µmOperating Frequency (Hz): 2 (Standard), 5, 10Pressure Range (MPa): 2 (Standard), upgradeable to 5Speed of Measurement and Control: 5 /10kHz Sample Sizes (mm): 38, 50, 70, 100 (other sizes available on request up to 300)

Tests that can be Performed:Consolidated drained (CD), consolidated undrained (CU), consolidation (Triaxial), dynamic cyclic loading of samples under either load or strain, slow cyclic testing, quasi-satic (low speed/creep) tests, stress paths, K-Zero and user defined waveforms.

Upgrade Options:Dynamic cell pressure, larger sample sizes up to 300mm diameter, higher cell pressure up to 5MPa, Bender element system (Vertical, Horizontal, S and P waves), Hall Effect Local Strain, LVDT local strain, unsaturated testing and temperature controlled testing.

Overview: The Advanced Dynamic Triaxial Testing System (DYNTTS) is a high-end testing apparatus combining a triaxial cell with a dynamic actuator capable of applying load, deformation and stresses at up to 10Hz.

The axial axis is screw-driven from an integral base unit housing the motor drive. Axial force and axial deformation are applied through the base of the cell.

Standards:ASTM D-3999 ASTM D-5311



Key Features: Benefits to the User:Dynamic control of axial displacement or axial force to 10Hz, sinusoidal waveform:

Direct (dynamic, 10Hz) closed loop control of axial displacement, axial force and cell pressure.

Optional dynamic control of radial stress to 10Hz, sinusoidal waveform:

The dynamic control of cell pressure means that for those tests where the cell pressure is constant but the axial actuator is moving dynamically, the cell pressure actuator automatically adjusts the volume of oil in the cell to maintain a constant cell pressure. Or it can be used to cycle the cell pressure.

Optional interchangeable load cells:To accommodate soft to very stiff soils with ranges of 28, 100 and 250kN. The load frame is supplied with an external load cell to match the model maximum load range as standard.

Load frame strength: GDS load frames are extremely stiff to allow minimum backlash at the point of sample shearing.

Tests that can be Performed:Axial compression, axial extension, cyclic loading, cyclic displacement, optional cyclic cell pressure, static load and static displacement.

Upgrade Options:Triaxial testing, bender element system (Vertical, Horizontal, S and P waves), hall effect local strain or LVDT local strain, unsaturated testing and temperature controlled.


Axial Force Accuracy: <0.1% of load cell range (i.e. 1N for 10kN load cell)Axial Force Resolution: 16 bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell)Data Acquisition (Built In): 16bit - 4 channel where load cell is Channel 1Displacement Accuracy: 0.05% of full rangeDisplacement Range (mm): 50 or 100Displacement Resolution: <3 µmLoad Range (kN): 28, 100, 250Operating Frequency (Hz): 0 - 10Sample Sizes (mm): Dependant on test type / cell selection, up to 300mm diameterWeight Approx (kg): 28kN (200kg), 100kN (1800kg), 250kN (3000kg)

Overview: The GDS Hydraulic Loading Frames (GDSHLF) are load frames with a dynamic hydraulic actuator mounted on the cross beam for axial loading and an optional second actuator for dynamic radial stress loading. The system is capable of dynamically controlling axial displacement or axial force and can be synchronised with an optional dynamic cell pressure actuator (radial stress) to give advanced capability of dynamic stress path testing. The GDSHLF is ideal for performing tests on large particle sizes such as ballast.

Standards:

Hydraulic Axial/Radial Loading Frame (HLF28), (HLF100) and (HLF250)

ASTM D-3999




Flexible system capacity: Specimen size, load and pressures can be selected to suit specification and budget.

Interchangeable (internal submersible) load cells:

Load cells to accommodate very soft to very stiff soils with ranges of 8, 16, 25, 32, 64, 128 and 250kN are available. The load frame is supplied with an external load cell to match the model maximum load range as standard (100 or 250kN).

GDSDCS (dynamic control system): For data acquisition and control, 8 channels of expandable accurate high speed acquisition and control.

Direct closed-loop dynamic control of axial displacement or axial force to 10Hz, sinusoidal, triangular or user defined waveform:

Accurate and flexible control options.

Tests that can be Performed:Consolidated drained (CD) triaxial, consolidated undrained (CU) triaxial, consolidation (Triaxial) dynamic, cyclic loading of samples under either load or strain, slow cyclic testing, quasi-static (low speed/creep) tests, stress paths, resilient modulus tests and user defined waveforms.

Upgrade Options:Sample volume measurement by HKUST, bender element system (Vertical, Horizontal, S and P waves), LVDT local strain and unsaturated testing.


Axial Force Accuracy: <0.1% of load cell range (i.e. 10N for 100kN load cell)Axial Force Resolution: 16bit (i.e. <0.4N for 10kN load cell, <1.5N for 40kN load cell)Displacement Accuracy: <0.15% (i.e. <0.15mm)Displacement Range (mm): 100Displacement Resolution: 16bit (i.e. <3µm)Load Range (kN): 100, 250Operating Frequency (Hz): 0 to 10Sample Sizes (mm): 300 (standard)

Overview: The Large Diameter Cyclic Triaxial Testing System (LDCTTS) is a hydraulically actuated load frame combined with a large diameter triaxial cell suitable for testing samples with large particle sizes such as railway ballast. The system is capable of monotonic (static) and dynamic triaxial tests as well as other advanced triaxial tests.

Standards:

Large Diameter Cyclic Triaxial Testing System (LDCTTS)

ASTM D-3999 prEN13286-7 AASHTO t294/T-307



Key Features: Benefits to the User:Stress or strain is applied to a 75mm x 75mm x 150mm sample independently on three axes:

Two pairs of matched dynamic rams for axes 1 and 2, and a confining fluid provides pressure for the 3rd axis on load readings.

Ram specification: Each ram has its own internal submersible load cell and displacement transducer to ensure friction effects are minimised.

Electro-mechanical actuators as standard:

Electro-mechanical actuators provide an easier to use and environmentally friendly solution for accurate testing to 5Hz. Electro-mechanical actuators do not require a hydraulic power pack to be present, hence no requirement to service a powerpack or to protect system users from noise generated by a powerpack.

Custom designed optional hydraulic actuators:

The hydraulic actuators have been custom designed by GDS to be seal-less with hydrostatic bearings. This improves the actuator performance (up to 10Hz) and reduces whole-life servicing costs as there are no piston seals to replace. Each actuator pair can be controlled in “static-mode” with either constant, ramp or slow cyclic targets in terms of load, stress or displacement.

Sample preparation:Full sample preparation equipment for cohesive and non-cohesive samples is provided with the system including a specially designed soil lathe for producing cuboidal samples.

Upgrade Options:Hydraulic 28kN actuators (10Hz), electro-mechanical 10/20kN actuators (5Hz), bender element system (vertical, horizontal, S and P waves), LVDT local strain and proximitor (axis 3 only), unsaturated testing and dynamic cell pressure (5Hz).

Tests that can be Performed:Fully independent control of axis 1 and 2 for load, stress, displacement and strain, stress control on axis 3 via cell pressure. Axis 1 and 2 can be controlled at up to 5Hz or 10Hz depending on the model selected (electro-mechanical vs hydraulic).


Data Acquisition: 16 Bit, 16 ChannelPressure Range (MPa): 2Load Range (kN): 5, 10, 20 - Electro-mechanical

28 - Hydraulic

Overview: The GDS True Triaxial Apparatus (GDSTTA) has the defining characteristic that, unlike conventional triaxial apparatus, all three principal stresses can be controlled independently, rather than just two in a conventional triaxial system. This allows a wider range of complex stress paths to be performed. This dynamic cyclic system is powered by advanced electro-mechanical actuators or optional hydraulic actuators and is an extremely sophisticated research tool.

Vertical and one horizontal axis are loaded via the dynamic actuators (axis 1 and 2), stress control is provided for the 2nd horizontal axis, (axis 3) via cell pressure.

True Triaxial Apparatus (GDSTTA)


Customer Testimonials

Read a sample of our customers feedback below.

“I would like to thank you personally for your outstanding support, control, demonstration and training of the ELDYN. Working more than 12 hours per day with you and with Orestis (NEOTEK) we learnt a lot and we are all grateful for your efforts and dedications. It truly made a difference! Thank you very much!” “I have been dealing with GDS Instruments for more than 10 years in the UK and Canada. During my dealings with the company they have been highly professional, providing excellent service and products. We have compared the products and service from a number of other vendors as part of our purchasing procedures, using a range of metrics and GDS consistently out perform their competitors. Their maintenance procedures and after sales service are also excellent. I have no hesitation in recommending GDS Instruments for soil testing instrumentation and apparatus.”

“I have had an exceptional experience with GDS. I was hired in 2003 to bring a geotechnical lab back to life after 5 years of inactivity. Through the unbelievable technical support and because of the quality of GDS’s products the original advanced triaxial system purchased in 1989 is working without a problem. I continue to use GDS and have confidence that their products will provide me with high quality data. The service and products provided by GDS are simply second to none.”

“Your technical support has been exceptional, rapid, detailed, and on target, even for a small customer like me. Please feel free to pass along my contact information to whomever you wish.” “I have used GDS’s LVDT (Local Strain Transducers) system to study Chicago clay samples for the past three years at Northwestern. The LVDT system allowed me to measure the strains directly on my test specimen. By using it, I could minimize uncertainties in interpretation from apparatus compliance, tilting of the specimen and the imperfect platen-sample bedding. Furthermore, the accuracy, precision and resolution level of the device are one of the major factors in my successful research. I can recommend GDS’ LVDT’s as a reliable internal measurement device.

“I must say that I have had an excellent experience with GDS. All of your staff have been extremely helpful and responsive to all of my requests. When I originally purchased the Bender Element accessories, the GDS staff did an excellent job in providing shop drawings and manuals to be used in modifying my existing triaxial system. I will certainly be using GDS again in the future. Thank you for your past assistance.”

“My first purchase was based on reference from a colleague; since then I have continued to purchase from GDS because, mainly, of the attention to detail and flexibility in system design, as well as tailored customer service for hardware and software.”

“I wish all instrument companies I dealt with were as responsive and capable as GDS.”

“I am very happy to provide a reference. You guys are *stars*! I am a minor GDS customer, but you have always been extremely supportive, knowledgeable, and speedy in helping me with questions.”

“FYI - we are currently testing more samples in our GDS-based system, this will be the 5th student to do a thesis using your equipment in my lab.” “Thanks very much for the information. The support and service from GDS is excellent and very much appreciated.”

“I would very much like to stay in touch as I am sure we can do business again. I am always impressed with the professionalism of the team at GDS”.

“I would like to thank you for the outstanding service regarding to the pressure-volume controller.”

“I will happily confirm the quality and function of the equipment, as well as prompt and very professional support!”

“Thank you very much, and I am certainly pleased to be doing business with GDS Instruments.”

GDS InstrumentsUnit 32 Murrell Green Business Park,London Road, Hook,Hampshire, UK, RG27 9GR.

Tel: +44 (0)1256 382450Fax: +44 (0)1256 382451Email: [email protected]: www.gdsinstruments.com

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