Triaxial Testing Equipment, 50kN, Automatic (3 Cell Version)
NL 5019 X / 005

Standard : ASTM D4767, ASTM D2850, ASTM D7181, BS 1377-7, BS1377-8

Automated Triaxial Testing Equipment

Triaxial Testing Equipment is used to measure the behavior of soils under different stress-strain and shear strengths, providing soil insights into their mechanical properties, including strength and deformation characteristics. The data is used for many soil engineering purposes such as ground, foundations, slopes, excavations, and embankments.

The soil test sample undergoes different levels of confining pressure while applying stress along its vertical axis, with fluid pressure applied in perpendicular directions. Deformations are recorded until the sample fails, enabling engineers to replicate diverse stress conditions encountered in real-world scenarios. By measuring the soil's response to these stresses, engineers can determine parameters such as shear strength, cohesion, and internal friction angle, which are crucial for designing foundations, retaining structures, and other geotechnical projects.

The Fully-Automatic Triaxial System further enhances this process by automating the triaxial test testing procedures with the automated control system, sensor automated checking, and data acquisition capabilities. These systems streamline the process of conducting triaxial tests by automating various stages of the testing procedure, from sample preparation to data collection and analysis. The range of the Triaxial Loading Frame has been designed to be used as part of the computer-controlled triaxial system with a stress path Triaxial Testing System or as a stand-alone unit. Consists of a Triaxial Loading Frame and an Advanced Pressure Volume Controller (APVC). Load frames are built up with the LCD graphical display and panel keypad.

Test Module of Automated Triaxial Testing Equipment 50kN (3-Cell Version)

• Data Acquisition Module Back Pressure Saturation Test; 
• Consolidation in the same direction and consolidation in different directions (pre-contact) test; 
• Consolidate – undrained test (U-U test); 
• Consolidate – undrained test (C-U test); 
• Consolidate – drainage test (C-D test); 
• Triaxial creep test Stress path triaxial test (Optional) 
• K0 Consolidation (Optional) 
• Temperature-controlled triaxial test (Optional)

A) Triaxial Load Frame

Triaxial Load Frame is used to apply axial and confining pressures to the soil sample while allowing for precise control and measurement of these pressures. This frame is engineered with rigidity, durability, low noise, and smooth operation in mind. It features a stepper motor coupled with a worm gear drive system to provide a reliable power source.

Key Components of the Triaxial Load Frame include upper and lower limit devices, ensuring safe and controlled testing conditions. Axial deformation is accurately measured and collected using a high-precision displacement sensor, while axial load is monitored via force sensors, recording various parameters such as axial load, confining pressure, deformation, and pore water pressure throughout the testing process. Additionally, to ensure the safety of both personnel and equipment, the Triaxial Load Frame machines are equipped with overload protection mechanisms.

Key Features of Triaxial Load Frame

• Fitted with internal pressure transducer. 
• The Loading Platen is made is made from stainless steel. 
• All external parts are either stove-enamel painted or chrome-plated for corrosion protection. 
• Comprised of a rigid chromed steel twin-column construction for rigidity at high loads. 
• High displacement sensor to measure deformation with 100mm range at the accuracy of ± 0.003mm. 
• Built with PLC Control mode adopts LCD graphics display in English. 
• Multifunctional keyboard input. Convenient and quick to operate. 
• Built-in ADVC Unit

Technical Specification of Triaxial Load Frame

B ) Advanced Pressure Volume Controllers (Built-in version)

The Advanced Pressure Volume Controller is very easy to use and an ideal solution for the most modern laboratories. When used with Test Master Loader, data loggers, and software, they can be controlled from a computer to form part of a complete automated triaxial testing system. They may also be used as stand-alone units that are fully functioning with or without computer control. All the devices have their computer interface. The devices come complete with internal volume and pressure transducers. Both channels are pre-calibrated, they can generate pressures up to 2000kPa (20 bar) and provide a maximum volume measurement of 100ml which is readable to 0.001ml.

Features of Advanced Pressure Volume Controllers

• Fitted with internal pressure transducer. 
• Pressure can be ramped up or down at a selected rate in kPa per minute. 
• Pressure or volume can be set, and maintained, at either kPa or ml respectively. 
• Max. Volume capacity of 100ml, readable to 0.001ml. 
• Protected transducer configuration and calibration. 
• Non-volatile storage of calibration and control parameters. 
• Quiet operation. 
• The advanced microprocessor controls the screw pump for the precise regulation and measurement of fluid pressure and volume change. 
• The fluid is de-aired water. 
• The advanced microprocessor-based electronics include: 
  • 1) Fast 16bit A/D converter
  • 2) Serial port for computer control

Technical Specification of Advanced Pressure Volume Controllers

Triaxial Load Cell 50kN

Triaxial Load Cell used to measure the axial force applied to a specimen in triaxial cell (supplied comes with a connector attaching to the crosshead of load frame). Top and Bottom Cell Caps are made in aluminum alloy and the transparent cell cylinder is made of high-resistance acrylic material. It is easy to assemble and dismantle by quick clamping rods. The bottom cell cap is supplied with three inlet valves, Back Pressure, Cell Pressure, and Pore Pressure. A003 can be used for specimen range with diameters 38mm x 76mm and 50mm diameter x100mm and 70mm diameter x140mm.

Technical Specification of Triaxial Load Cell 50kN

Note: Base Adapters, rubber membranes Top Cap, Porous Stone, etc should be ordered separately. Refer table for accessories.

C) Stress Path Triaxial Testing System (V3.11)

Stress Path Triaxial Testing System (V3.11) is the software that represents a breakthrough in geotechnical laboratory control software. It can choose particular test modules for any international Standards requirements. Flexibility in hardware configuration means that the testing quality will depend on the hardware attached, not on the software.

Features of Stress Path Triaxial Testing System (V3.11)

• Ability to batch multiple tests by taking a queue. 
• The data displayed can be changed during testing. 
• Able to plan the future development of laboratory testing within a framework. 
• Comply with International Standards. 
• Modules of testing available are general Triaxial Testing including Unconsolidation Undrained (UU), Consolidation Undrained (CU), and Consolidation Drained (CD).

Accessories of Triaxial Testing Equipment

Optional Accessories: De-airing Tanks 

De-airing Tanks are used with Triaxial Test Systems to remove entrapped air in the water when connected to the vacuum pump. The de-airing water system produces not less than 10L batches of de-aired water without the use of heat, combined with mechanical agitation and vacuum evacuation.

Technical Specifications of De-airing Tanks

Standards

• ASTM D4767 - Standard Test Method for Consolidated Undrained Triaxial Compression Test for Cohesive Soils: This ASTM standard provides guidelines for performing consolidated undrained triaxial compression tests on cohesive soils. It outlines the procedure for preparing soil samples, applying confining pressure, and conducting the test to determine shear strength parameters.
• ASTM D2850 - Standard Test Method for Unconsolidated-Undrained Triaxial Compression Test on Cohesive Soils: Specifies the procedure for conducting unconsolidated-undrained triaxial compression tests on cohesive soils. This test method is used to determine the undrained shear strength of soils under rapid loading conditions, without prior consolidation.
• ASTM D7181 - Standard Test Method for Consolidated Drained Triaxial Compression Test for Soils: The procedure for conducting consolidated drained triaxial compression tests on soils. The test is performed under conditions where pore water pressure is allowed to dissipate during shearing, providing data on drained shear strength properties of soils.
• BS 1377-7 - Methods of Test for Soils for Civil Engineering Purposes. Shear Strength Tests (total stress): Part 7 of the British Standard BS 1377 provides methods for conducting shear strength tests on soils for civil engineering purposes. It includes procedures for conducting triaxial compression tests under total stress conditions to determine shear strength parameters.
• BS 1377-8 - Methods of Test for Soils for Civil Engineering Purposes. Shear Strength Tests (effective stress): Part 8 of BS 1377 focuses on conducting shear strength tests under effective stress conditions. This standard provides guidelines for performing triaxial compression tests where pore water pressure is controlled to simulate field conditions, allowing the determination of effective stress parameters.

Types of Triaxial Tests

Unconsolidated Undrained (UU) Test:

• In the UU test, the soil sample is not subjected to any consolidation (i.e., no application of axial stress to compact the sample) before the test begins.
• The confining pressure is applied to the soil sample, and then it is rapidly sheared without allowing time for consolidation.
• During the shearing process, pore water pressure is allowed to build up without being dissipated (undrained condition).
• This test is typically used to assess the undrained shear strength of soils, which is crucial for analyzing the stability of quick-loading conditions such as during an earthquake or rapid construction.

Consolidated Undrained (CU) Test:

• In the CU test, the soil sample is first subjected to a process of consolidation, where an axial load is applied gradually over time to compact the soil.
• Once the consolidation process is complete, the confining pressure is applied to the soil sample, but no drainage of pore water is allowed during the shearing process.
• The CU test is used to determine both the drained and undrained shear strength of soils under different levels of confinement.
• This test is particularly useful for analyzing soil behavior in conditions where drainage is restricted, such as beneath the foundation of a structure.

Consolidated Drained (CD) Test:

• In the CD test, similar to the CU test, the soil sample is first subjected to consolidation to remove any excess pore water and achieve a stable state.
• However, in the CD test, drainage of pore water is allowed during the shearing process, meaning that excess pore water pressure is dissipated as the test progresses.
• The CD test is used to determine the drained shear strength of soils under different levels of confinement.
• This test is relevant for analyzing soil behavior in situations where drainage is unrestricted, such as in embankments or slopes subjected to steady-state loading conditions.

Test Procedure of Triaxial Testing Equipment

• Sample Preparation:
• Soil samples are carefully prepared according to the required specifications, such as diameter, height, and density. Special attention is given to ensuring that the sample is representative of the in-situ soil conditions.
• The sample is usually trimmed to the desired size and shape using cutting tools and molds.
• Sample Installation:
• The prepared soil sample is placed inside the triaxial cell, a cylindrical chamber equipped with porous stones or filters at both ends to allow water to flow freely while preventing soil particles from escaping.
• The sample is then saturated with water to ensure that it is fully saturated before testing begins. Saturation is typically achieved by applying water pressure or by allowing the sample to soak in water over a period of time.
• Confining Pressure Application:
• Once the sample is saturated, the confining pressure is applied to the soil sample using a pressure control system. This pressure is exerted uniformly around the sample to simulate the lateral stress that soil experiences in the field.
• The confining pressure is gradually increased to the desired level while ensuring that the sample remains intact and does not deform excessively.
• Consolidation (for CU and CD Tests):
• For Consolidated Undrained (CU) and Consolidated Drained (CD) tests, a process of consolidation is performed before shearing the sample.
• During consolidation, an axial load is applied to the sample at a controlled rate to remove excess pore water and achieve a stable state. The rate of consolidation depends on the specific test requirements and soil properties.
• Shearing:
• After consolidation (for CU and CD tests) or immediately (for UU tests), the shearing process begins. An axial load is applied to the soil sample at a constant rate while monitoring the axial deformation.
• In UU tests, drainage of pore water is not allowed during shearing, while in CD tests, drainage is permitted. CU tests fall in between, allowing drainage to some extent.
• The shearing continues until the desired deformation or failure criterion is reached, such as a specified axial strain or shear stress.
• Data Collection:
• Throughout the test, various parameters are measured and recorded, including axial load, confining pressure, axial deformation, pore water pressure, and volume change.
• Real-time data acquisition systems are often used to monitor these parameters and ensure accurate measurements.
• Data Analysis:
• Once the test is completed, the collected data is analyzed to determine key soil properties such as shear strength, cohesion, internal friction angle, and permeability.
• Analysis may involve plotting stress-strain curves, calculating failure envelopes, and interpreting the results in relation to the specific engineering application.
• Reporting:
• Finally, the test results are compiled into a comprehensive report, detailing the testing procedure, equipment specifications, sample characteristics, test results, and interpretations.
• The report provides valuable information for engineers and geotechnical professionals involved in designing and analyzing soil structures and foundations.