Triaxial Testing System Static and dynamic

Static triaxial press for UU, CU and CD soil tests and dynamic triaxial press for resilient modulus and permanent deformation, in four models.

Request a quote

The Biopdi triaxial testing machine performs the triaxial test of soils: it compresses a cylindrical specimen confined by pressure inside a triaxial cell and measures force, displacement, pore pressure and volume change. The static triaxial testing machine (PTE-50k), electromechanical, 50 kN, with a rate of 0.001 to 30 mm/min, performs the UC, UU, CU and CD tests according to ASTM D2166, D2850, D4767 and D7181. The dynamic triaxial testing machine (PTD-20k), pneumatic, 20 kN, applies repeated loading for resilient modulus and permanent deformation according to DNIT 134/2018-ME, 135/2018-ME, 179/2018-IE and 181/2018-ME (Brazilian road agency methods).

Both are manufactured by Biopdi in São Carlos, Brazil, with in-house software, and come in a basic or automatic version, depending on the pressurization system. The procedure for each test, with formulas and worked examples, is in the articles on the triaxial test and the resilient modulus.

Static triaxial testing machine

Dynamic triaxial testing machine

Static and dynamic triaxial testing system

Triaxial testing system models

Static or dynamic, each in a basic or automatic version.

Basic static triaxial testing system

UC, UU, CU and CD; manual pressurization

Basic dynamic triaxial testing system

MR and permanent deformation; manual confinement

Automatic static triaxial testing system

UC, UU, CU and CD; 1,600 kPa pressurizer

Automatic dynamic triaxial testing system

MR and permanent deformation; automatic confinement

Triaxial testing system specifications

Data from the manuals of the static triaxial testing system (PTE-50k) and the dynamic one (PTD-20k).

Static triaxial testing system

Model	PTE-50k, static triaxial load frame
Drive	Electromechanical, servo-controlled; ball screw actuator
Frame	Two-column (two threaded screws for adjusting the fixed crosshead), 400 mm between columns
Capacity	50 kN (11,240 lbf)
Test speed	0.001 to 30 mm/min
Position measurement	Optical encoder, 0.001 mm resolution
LVDT	50 mm stroke, 0.01 mm resolution
Channels	Force and displacement on the machine; up to four strain channels (0 to 10 VDC LVDT or extensometer)
Load cell	50 kN, interchangeable, class 1 or 0.5
Safety	Upper and lower limit switches and emergency stop button (NR 12, the Brazilian machinery safety standard)
Communication and software	USB; Windows 10, 2 GB RAM (4 GB recommended)
Power supply	220 V, 60 Hz, 720 W
Dimensions	585 × 589 × 1,563 mm (depth × width × height)

Dynamic triaxial testing system

Model	PTD-20k, dynamic triaxial load frame
Drive	Pneumatic, microprocessor-controlled, with data acquisition by the software
Capacity	20 kN (4,496 lbf), with a 20 kN load cell
Loading frequency	1 to 5 Hz
Pneumatic supply	10 bar, with air reservoir
Piston stroke	10 mm
Control panel	High and low pressure regulators and piston up/down switch
Frame	Two screws with vertically adjustable crossbeam
Connections	TCP-IP network, USB and four sensor inputs
Power supply	220 V
Dimensions	1,342 × 500 × 714 mm (height × width × length)

The drawings in the manuals give the dimensions of the two presses: the static press is 1,563.40 mm high with 400 mm between columns; the dynamic press is 1,342 mm high with a 500 × 714 mm base.

Dimension drawing of the Biopdi static triaxial press: overall height of 1,563.40 mm, width of 588.75 mm and 400 mm between columns — **Dimensions of the static triaxial testing machine.** Overall height of 1,563.40 mm, width of 588.75 mm and depth of 585.15 mm; base height of 429.78 mm; 400 mm between columns; fixed crosshead of 400 × 75 × 65 mm.

Dimension drawing of the Biopdi dynamic triaxial testing machine: height of 1,342 mm, width of 500 mm and length of 714 mm — **Dimensions of the dynamic triaxial testing machine.** Height of 1,342 mm, width of 500 mm and length of 714 mm, with a 400 mm base.

Cells, pressure controllers and fixtures

Fixture	Use	Features
3" static triaxial cell (CTE-16b)	UU, CU and CD	Acrylic with aluminum base and top; 38 and 76 mm specimens; up to 1,600 kPa; ball valves for cell pressure, back pressure and pore pressure
Static triaxial cell (CTE-10b) and 4" cell	UU, CU and CD	Acrylic and aluminum, 619 mm high and Ø 230 mm
1,600 kPa pressure controller (PRS-1k6)	Confining pressure, back pressure and volume change	Water; motor, lead screw and 150 cm³ hydraulic cylinder; 0.1 kPa resolution; 1,600 kPa pressure and pore pressure transducers (0.5%) and volume change sensor; overpressure protection; 220 V
Dynamic triaxial cell (CTD-200kPa)	Resilient modulus and permanent deformation	Acrylic and aluminum; air confinement up to 200 kPa; two LVDTs and load cell inside the chamber
Pneumatic pressure controller (PZP-200kPa)	Confining stress for the dynamic triaxial	Air from an external compressor; pressure regulator and pressure switch with cell pressure readout in kPa; valves and hoses
Diametral compression (CDD-100)	Resilient modulus of asphalt mixtures (DNIT 135)	Steel and aluminum, base with an angled groove to seat the specimen, two LVDTs
MR DNIT 181 device, Ø 100 and Ø 150 mm	Resilient modulus of chemically stabilized material (DNIT 181)	Upper and lower bases with wing nuts for the pair of 10 mm LVDTs, attached at the middle third of the specimen

Static triaxial cells

The static press cells, as shown in the manuals: the CTE-10b in an exploded view, with the name of each assembly; the 3-inch cell (CTE-16b) with dimensions and mounted on the press; and the 4-inch cell with dimensions.

Dimension drawing of the Biopdi CTE-16b 3-inch static triaxial cell: 614 mm high and Ø230 mm — **3" static triaxial cell (CTE-16b).** Up to 1,600 kPa, for 38 and/or 76 mm test specimens. Height of 614 mm, Ø230 mm base and 316 mm width including the valves. Supplied with pedestal, top cap, acrylic base disc, porous stones and latex membranes.

Biopdi 3-inch static triaxial cell mounted in the load frame, with the load cell coupling on the shaft — **3" cell mounted in the load frame.** The cell sits on the loading platen, with the shaft fitted into the load cell coupling. The ball valves on the base connect the confining pressure, the saturation back pressure and the pore pressure measurement.

Dimension drawing of the Biopdi 4-inch static triaxial cell: 619 mm high and Ø230 mm — **4" static triaxial cell.** Acrylic and aluminum. 619 mm high: 376 mm for the chamber and 243 mm for the shaft bracket; Ø230 mm.

Dynamic triaxial cell

The dynamic press cell holds the load cell and the two LVDTs inside the chamber and works with air up to 200 kPa. Left, the parts; right, the dimensions.

Dimension drawing of the Biopdi dynamic triaxial cell: height of 520 mm, 640 mm with the load cell, Ø277 mm and 360 mm with the valves — **Dynamic triaxial cell dimensions.** 520 mm high, or 640 mm to the top of the load cell; Ø277 mm, or 360 mm with the valves.

Pressure controllers

The 1,600 kPa water pressurizer (PRS-1k6) serves the automatic static press; the pneumatic pressurizer (PZP-200kPa) applies the confining pressure with air on the dynamic press. The figures show each one with its parts and dimensions.

Biopdi PRS-1k6 1,600 kPa water pressure controller for the automatic static triaxial testing system — **1,600 kPa pressure controller (PRS-1k6).** Connected to a water supply, it keeps pressure and volume uniform in the test specimen, with protection against pressure and volume overload. Capacity of 1.6 MPa, volume of 150 cm³ and 0.1 kPa resolution in pressure measurement and control; 220 V power supply.

Labeled parts of the Biopdi 1,600 kPa pressure controller: control membrane, motor, motor guard, lead screw, LVDT and pressure sensor — **Parts of the 1,600 kPa pressure controller.** Control membrane at the top, where the pressure is programmed; motor with guard, which drives the piston through the lead screw; LVDT; pressure sensor at the outlet, connected to the cell. The electrical components sit inside the 120 × 80 mm rectangular steel tube (metalon) base.

Dimensions of the Biopdi 1,600 kPa pressure controller: 656 mm long, 163 mm wide and 237 mm high — **Dimensions of the 1,600 kPa pressure controller.** 656 mm long, 163 mm wide and 237 mm high.

Biopdi PZP-200kPa pneumatic pressure controller with pressure regulator, pressure gauge and valves labeled — **PZP-200kPa pneumatic pressure controller.** Air from an external compressor enters through one of the valves; the operator sets the pressure on the controller, and the pressure switch displays the confining pressure. Polycarbonate label. Dimensions: 196 × 136 × 148 mm.

Front panel of the Biopdi pneumatic pressure controller with the confining pressure gauge in kPa and the pressure regulator — **Pneumatic pressure controller panel.** Confining pressure switch (the value on the display is illustrative) and pressure controller, with the − and + directions marked on the label. On the left, the air inlet and outlet valves.

Dimensions of the Biopdi pneumatic pressure controller: 196 mm long, 136 mm wide and 148 mm high — **Pneumatic pressure controller dimensions.** 196 mm long, 136 mm wide and 148 mm high.

Resilient modulus fixtures

On the dynamic press, the MR DNIT 181 fixture attaches the pair of LVDTs to roller-compacted concrete specimens of Ø100 and Ø150 mm, and the diametral compression fixture (CDD-100) measures the resilient modulus of asphalt mixtures according to DNIT 135.

Biopdi DNIT 181 resilient modulus (MR) fixture mounted on a Ø100 mm RCC test specimen, with a pair of 10 mm LVDTs — **DNIT 181 MR fixture, Ø100 mm.** For roller-compacted concrete (RCC) test specimens. Upper LVDT support base and lower tip support base, held by wing nuts and spaced over the middle third of the height; pair of 10 mm LVDTs. 200 × 190 × 86.6 mm, 0.415 kg.

Biopdi DNIT 181 resilient modulus (MR) fixture for a Ø150 mm RCC test specimen, with a pair of 10 mm LVDTs — **DNIT 181 MR fixture, Ø150 mm.** The same setup for Ø150 mm test specimens: LVDT and tip support bases with wing nuts and a pair of 10 mm LVDTs. 260 × 241.2 × 86.6 mm, 0.497 kg.

Biopdi CDD-100 diametral compression fixture with test specimen, two LVDTs, supports, base and crosshead labeled — **CDD-100 diametral compression fixture.** Resilient modulus of asphalt mixtures (DNIT 135, Brazilian highway agency test method). Steel and aluminum: the crosshead is fixed to the press, the support base has an angled groove to seat the test specimen, and the two LVDTs sit on the side supports, one on each side of the specimen.

Dimensions of the Biopdi diametral compression fixture: 500 mm long, 231 mm high and Ø120 mm — **Diametral compression fixture dimensions.** Dimensions from the manual: 500 mm long, 231 mm high and Ø120 mm.

Triaxial testing system tests

What each test measures, with which system and fixture, and under which standard.

Test	What it measures	Press and fixture	Standard
Unconfined compression (UC)	Unconfined compressive strength of cohesive soil, without confinement	Static load frame, load cell and LVDT	ASTM D2166
UU triaxial	Undrained shear strength (su) in total stresses	Static load frame, triaxial cell and pressure controller	ASTM D2850
CU triaxial	Effective parameters c' and φ' with pore pressure measurement and B-value check	Static load frame, triaxial cell and pressure controller with pore pressure transducer	ASTM D4767
CD triaxial	Effective parameters c' and φ' with volume change measurement	Static load frame, triaxial cell and pressure controller with volume change sensor	ASTM D7181
Resilient modulus of soils and crushed stone	MR = σd / εr under deviator stress pulses at constant confining pressure	Dynamic load frame, dynamic triaxial cell and pneumatic pressure controller	DNIT 134/2018-ME
Permanent deformation	Accumulated deformation over at least 150,000 cycles	Dynamic load frame, dynamic triaxial cell and pneumatic pressure controller	DNIT 179/2018-IE
Resilient modulus of asphalt mixtures	MR by repeated-load indirect tensile (diametral compression) testing	Dynamic load frame and diametral compression fixture	DNIT 135/2018-ME
Resilient modulus of chemically stabilized materials	MR of soil-cement, cement-treated crushed stone (BGTC), roller-compacted concrete (CCR) and similar materials	Dynamic load frame and DNIT 181 MR fixture	DNIT 181/2018-ME

The step-by-step procedure for UU, CU and CD, with the B-value check and the shear rate calculation, is in the article on the triaxial test; the DNIT 134 stress pairs, the DNIT 135 diametral compression and permanent deformation are in the article on resilient modulus.

STATIC TRIAXIAL TESTING SYSTEM

The static triaxial press performs the tests that measure the soil's shear strength parameters: cohesion and internal friction angle, in total or effective stresses.

The triaxial compression test measures the mechanical properties of soils, such as sands and clays, and of rocks. It is used in civil construction and geotechnical engineering to obtain design parameters for foundations, slopes, dams and retaining structures.

The press performs unconfined compression (UC), unconsolidated undrained (UU), consolidated undrained (CU) and consolidated drained (CD) tests, conventional or saturated.

It is a servo-controlled machine for axisymmetric triaxial testing: the specimen receives the axial stress from the piston and the confining pressure from the water in the cell, and the test determines the cohesion and internal friction angle of the soil.

The frame has a base, two threaded screws for adjusting the fixed crosshead and a ball screw that drives the actuator, in ABNT 1020 and 1045 steel. Position is read by an optical encoder with 0.001 mm resolution, and the machine has force and displacement channels and accepts up to four strain channels for LVDTs or extensometers.

The drive is electromechanical, with a capacity of 5,000 kgf (49 kN) (other capacities on request). For the tests there are triaxial cells, load cells, LVDTs and the pressurization system. The software handles setup, configuration, data acquisition, analysis and test reports.

Standards met by the static triaxial testing system

The static triaxial testing system meets the following standards:

ASTM D2166: unconfined compression (UC)

ASTM D2850: unconsolidated undrained triaxial (UU)

ASTM D4767: consolidated undrained triaxial (CU)

ASTM D7181: consolidated drained triaxial (CD)

For other standards, get in contact us with our technical team. For more details on the triaxial test, visit our articles page.

Biopdi has its own technology to develop, manufacture and sell any type of soil testing equipment, so any machine parameter can be customized. Contact us to learn more.

Main components of the static triaxial testing system

Components that make up the static triaxial testing system.

50 kN electromechanical load frame

Water pressurization system, up to 1,600 kPa

Acrylic and aluminum triaxial cell

Load cell (submersible and non-submersible)

LVDT (submersible and non-submersible)

Static triaxial testing system - features

The figures from the PTE-50k manual show the press with the pressurizer, the parts labeled in the front and rear views and the front control panel.

Biopdi PTE-50k static triaxial testing machine, 50 kN, next to the 1,600 kPa water pressurizer — **PTE-50k static triaxial testing machine.** 5,000 kgf (49 kN) electromechanical press, with the water pressurizer beside it. The triaxial cell sits on the actuator, at the base, and the fixed crosshead is adjusted on the columns until the load cell coupling touches the cell shaft.

Labeled parts of the Biopdi static triaxial press: threaded rod, fixed crosshead, load cell assembly, actuator, front panel and connector panel — **Parts of the static triaxial testing machine.** Threaded rods for adjusting the height of the fixed crosshead; fixed crosshead with the load cell assembly; triaxial cell support on the actuator, which moves up and down on the ball screw; front control panel; at the rear, connector panel (load cell, sensors such as the LVDT, USB and power), cooling outlet and nameplate; Vibra-Stop anti-vibration feet.

Front panel of the Biopdi static triaxial testing machine with On/Off, Emergency, Home, Reference, Up and Down buttons — **Front panel.** On/Off powers the machine; Emergency stops the actuator immediately; Reference saves the current position as the zero point; Home returns the actuator to that position; Up and Down move the actuator base.

Technical features of the static triaxial testing system

Technical specifications of the static triaxial testing system.

Servo-controlled electromechanical twin-column press with ball screw drive

Distance between columns: 400 mm

Press capacity: 50 kN (11,240 lbf)

Speed and displacement control

Test speed: 0.001 to 30 mm/min

Displacement stroke: 100 mm

Position measured by optical encoder, with 0.001 mm resolution

Linear variable differential transformer (LVDT): 50 mm, 0.01 mm resolution

Up to four strain channels (0 to 10 VDC LVDT or extensometer)

50 kN interchangeable load cell, class 1 or 0.5 (other capacities on request)

Upper and lower limit switches and emergency stop button (NR 12, the Brazilian machinery safety standard)

Front panel with on/off switch and up, down, reference and home buttons

USB port for computer connection and control

Automatic stop on force drop, maximum force, displacement or strain

Digital data output

Benchtop model

Electrostatic powder coating for corrosion protection

Rubber feet for damping and vibration isolation

Power supply: 220 V, 60 Hz, 720 W

Manufactured in Brazil

12-month warranty against manufacturing defects (parts and accessories)

Comes with an operating manual in Portuguese

Main accessories of the static triaxial testing system

Accessories available for the static triaxial testing system.

LVDT (displacement transducer)

Linear variable displacement transducer; 50 mm stroke and 0.01 mm resolution

Load Cell

Interchangeable, in several capacities, submersible and non-submersible

Static Triaxial Cell

Acrylic and aluminum, 38 and 76 mm specimens, up to 1,600 kPa in the 3" model

Pressurization System

1,600 kPa water pressure controller, with pore pressure and volume change measurement

The figure from the static system manual shows the triaxial cell with its parts named and, next to it, the rendered view.

Static triaxial cell of the Biopdi press with labeled parts: top support, shaft, LVDT support, tie rods, knob screw and valves — **Triaxial cell of the static machine.** Hard aluminum with an acrylic chamber and radial seal: 76 mm test specimen diameter, 3.4 MPa working pressure and 300 cm³ volume capacity. At the top, the top support and the cell shaft, which takes the load cell, and the LVDT support; on the sides, the tie rods and knob screws; the quick-coupling ball valves carry the confining pressure, the saturation back pressure and the pore water pressure measurement.

Static triaxial testing system software

The software used with the static triaxial press has an interface for test setup and configuration, analysis and data acquisition.

Available tests: unconfined compression (UC), unconsolidated undrained (UU), consolidated undrained (CU) and consolidated drained (CD), conventional and saturated. Stress paths p, q or s, t, Mohr circles and tangent and secant lines on the stress × strain plot. Requires a computer with Windows® 10, 2 GB of RAM (4 GB recommended) and a USB port.

Screen 01 - software - static triaxial test

Setup tab

Communication field: Selects the USB communication port.

Test Type field: Sets the direction of movement and the speed of the actuator.

Manual Adjustment field: Moves the actuator manually at a set constant speed.

Specimen Cross-Section Area field: Sets the dimensions of the test specimens.

Automatic Stop field: Ends the test on force drop, maximum force, displacement or strain.

Sensors field: Enables the position, pressure and volume sensor readings.

Chart field: Enables export of the B-value, Consolidation, Shear and Stress Path charts.

Pore Pressure / Volume Change field: Controls acquisition of the volume (cm³) and pressure (kPa) measurements.

Save Location field: Saves the data while the test is running.

B-Value tab

Play button: Starts acquiring the pressure reading to check the B-value.

Reset button: Clears the previously acquired data.

Saturation: Degree of saturation of the specimen as a percentage (%).

Saturation (%) x Time (min) chart: Shows the degree of saturation over time.

Consolidation tab

Play button: Starts acquiring the volume reading to check the consolidation curve.

Delta V (cm³): Volume indicator.

Vmax1 (mm/min): Ideal rate for the shear stage.

Delta V (cm³) x Time (min) chart: Shows the volume change over time.

Parameters tab

Equipment parameter and calibration data, used only for technical service.

UU Test tab

Position (mm): Position indicator during the test.

Force (N): Force indicator during the test.

S1 / S3 (kPa): Axial stress applied at the top of the specimen and confining stress.

Strain (%): Strain of the specimen during the test.

Charts: Deviator Stress x Strain and Pore Pressure x Strain.

CU Test tab

Indicators: Position (mm), Force (N), S1/S3 (kPa), Strain (%), u (kPa).

Charts: Deviator Stress x Strain and Pore Pressure x Strain.

CD Test tab

Indicators: Position (mm), Force (N), S1/S3 (kPa), Strain (%), Delta V (cm³).

Charts: Deviator Stress x Strain and Delta V x Strain.

Stress Path Chart tab

p x q chart (kPa): Relationship between the normal stress and the shear stress on the plane of maximum shear stress.

Chart p' x q' (kPa): Relationship between the shear stress and the effective stress applied to the sample.

Static triaxial testing system videos

Videos of the static triaxial testing system.

DYNAMIC TRIAXIAL TESTING SYSTEM

The Biopdi dynamic triaxial press performs resilient modulus and permanent deformation tests, configured in the machine's dedicated software.

To do this, the machine applies different stress pairs to the specimen: cyclic deviator stresses, with adjustable frequency, and constant confining pressures.

The dynamic triaxial press (PTD-20k) is pneumatically driven and microprocessor-controlled, with electronic data acquisition by the software. The pneumatic system sits at the top of the machine, with high- and low-pressure regulators; below, two screws support the vertically adjustable crossbeam. It comes with an air reservoir and a 20 kN load cell.

The confining pressure is applied with air by the pneumatic pressurizer, up to 200 kPa. The dynamic triaxial cell holds two displacement sensors (LVDTs) and the load cell inside the chamber, next to the specimen.

Standards met by the dynamic triaxial testing machine

The dynamic triaxial testing machine meets the following standards:

DNIT 134/2018-ME: Paving: soils, determination of resilient modulus

DNIT 135/2018-ME: Asphalt paving: asphalt mixtures, determination of resilient modulus (diametral compression)

DNIT 179/2018-IE: Paving: soils, determination of permanent deformation (test instruction)

DNIT 181/2018-ME: Paving: chemically stabilized material, determination of resilient modulus (with the MR DNIT 181 device)

For other standards, get in contact with our technical team. The procedure for each standard is described in the article on resilient modulus.

Main components of the dynamic triaxial testing machine

Components of the dynamic triaxial testing machine.

Pneumatic actuator for cyclic loading

Pneumatic confining pressure pressurizer, up to 200 kPa

Triaxial cell for dynamic tests

20 kN (4,496 lbf) submersible load cell

Two submersible LVDTs for resilient displacement

Static and dynamic triaxial testing machine - features

The figures from the PTD-20k manual show the press, its labeled parts and the pneumatic system panel, where the operator sets the pressures and moves the piston.

Biopdi PTD-20k dynamic triaxial testing machine, pneumatic, with pneumatic system and air reservoir at the top — **PTD-20k dynamic triaxial testing machine.** Pneumatic system at the top, enclosed in sheet steel, with the air reservoir behind it; two lead screws and the vertically moving crosshead; support base. Supplied with the reservoir, a fixing wrench and a 20 kN load cell.

Labeled parts of the Biopdi dynamic triaxial press: front panel, pneumatic system, crosshead, threaded rod and support platen — **Parts of the dynamic triaxial testing machine.** Front panel and pneumatic system at the top; crosshead on the threaded rods; support platen at the base, which holds the dynamic triaxial cell or the test fixture.

Pneumatic system panel of the Biopdi dynamic triaxial press with high- and low-pressure regulators and a down/up selector switch — **Pneumatic system panel.** High-pressure and low-pressure regulators, pressure controller and the selector switch that moves the piston down and up to the test fixture.

Technical specifications of the dynamic triaxial testing machine

Technical specifications of the dynamic triaxial testing machine.

Microprocessor-controlled pneumatic load actuator

Two screws with vertically adjustable crossbeam

Capacity: 20 kN, with 20 kN load cell

Loading frequency: 1 to 5 Hz

Pneumatic supply: 10 bar, with air reservoir

Piston stroke: 10 mm

Two submersible LVDTs in the dynamic triaxial cell

Submersible load cell (can be changed)

Panel with high and low pressure regulators and piston up/down switch

Connections: TCP-IP network, USB and four sensor inputs

USB port for computer connection and control

Automatic stop on force drop, maximum force, displacement or strain

Digital data output

Benchtop model

Electrostatic powder coating for corrosion protection

Rubber feet for damping and vibration isolation

Power supply: 220 V

Manufactured in Brazil

12-month warranty against manufacturing defects (parts and accessories)

Comes with an operating manual in Portuguese

Main accessories for the dynamic triaxial testing machine

Accessories available for the dynamic triaxial testing machine.

LVDT

Linear displacement measurement, submersible and non-submersible

Load Cell

20 kN (4,496 lbf), submersible, inside the chamber

Dynamic Triaxial Cell

Acrylic and aluminum, air confinement up to 200 kPa, two LVDTs

Diametral Compression

Resilient modulus of asphalt mixtures (DNIT 135, Brazilian highway standard), with two LVDTs

Pressurization System

Confining pressure control for the triaxial cell

For the resilient modulus of chemically stabilized materials, such as soil-cement, cement-treated graded crushed stone and roller-compacted concrete, there is the MR DNIT 181 fixture (DNIT is Brazil's federal road agency), for 100 and 150 mm test specimens: top and bottom bases with wing nuts that hold the pair of 10 mm LVDTs on the middle third of the specimen.

Dynamic triaxial testing machine software

The dynamic triaxial testing software has an interface for setup and configuration, with preprogrammed routines for resilient modulus (DNIT 134/2018-ME and 135/2018-ME, Brazilian road standards) and permanent deformation (DNIT 179/2018-IE).

Requires a computer running Windows® 10. The machine connects via TCP-IP network or USB.

Screen 01 - software - dynamic triaxial test

General Controls

Start Test: starts the test according to the configured parameters.

PPC / PPS: points per cycle and points per second of actuation.

High Pressure: displays the high pressure value.

Force: load cell reading, in kgf.

Deviator Stress: deviator stress applied to the test specimen, in kPa.

Position: displacement value, in mm.

Settings Tab

Actuate Piston: applies the high-pressure load of the pneumatic actuator.

Frequency: sets the actuation frequency, between 1 and 5 Hz.

Specimen height, H0: test specimen height value.

Automatic Sd: automatically determines the Deviator Stress value.

Enable test: DNIT 134/2018-ME, DNIT 135/2018-ME or DNIT 179/2018-IE.

Table 1 / Table 2: stress pairs for conditioning and testing.

MR Test Tab

Sequence: shows the sequence of applied stress pairs.

Dh: resilient deformation, in mm.

MR: resilient modulus, in kPa.

Graph: displacement (mm) versus time (s), for each cycle.

Permanent Deformation Test tab

Information on the permanent deformation test, with Deformation vs. Time and Permanent Deformation vs. Cycle plots. The Parameters tab contains calibration data for technical service.

Dynamic triaxial testing system videos

Videos of the dynamic triaxial testing system.

Frequently asked questions

The most common questions about the triaxial testing system.

What is a triaxial testing machine?

It is the machine that compresses a cylindrical soil specimen, confined by pressure inside a triaxial cell, to measure shear strength (static triaxial test: UU, CU and CD) or stiffness under repeated loading (dynamic triaxial test: resilient modulus and permanent deformation). Biopdi manufactures the 50 kN static press, the 20 kN dynamic press and the configuration that combines both.

Which tests does the static triaxial testing machine perform?

Unconfined compression (UC, ASTM D2166) and the unconsolidated undrained (UU, ASTM D2850), consolidated undrained (CU, ASTM D4767) and consolidated drained (CD, ASTM D7181) triaxial tests, conventional or saturated. The software checks the B-value, records consolidation and plots the stress paths and Mohr circles.

What is the difference between the static and the dynamic triaxial testing machine?

The static press is electromechanical: it applies the load at a constant rate, from 0.001 to 30 mm/min, until the specimen fails. The dynamic press is pneumatic: it applies deviator stress pulses at 1 to 5 Hz without failing the specimen, to measure the resilient modulus (DNIT 134/2018-ME, the Brazilian road agency method) and the permanent deformation (DNIT 179/2018-IE) used in pavement design.

What is the speed range of the static triaxial testing machine?

From 0.001 to 30 mm/min. The slow end covers CU and CD shearing of clay, which is usually in hundredths of a millimeter per minute; the rate is calculated from the specimen's consolidation time, and the software shows the suggested rate in the consolidation tab.

What is the confining pressure of the triaxial testing machine?

On the static press, the Biopdi water pressurizer applies up to 1,600 kPa, with 0.1 kPa resolution, and the triaxial cells are rated for 1.0, 1.6 or 3.4 MPa, depending on the model. On the dynamic press, the cell and the pneumatic pressurizer work with air up to 200 kPa, above the highest confining stress in DNIT 134 (the Brazilian resilient modulus method), which is 140 kPa.

What test specimen size does the triaxial testing machine take?

The static triaxial cells take specimens of 38 and 76 mm diameter, with pedestal, top cap, porous stones and latex membranes for each diameter. In the dynamic triaxial test, DNIT 134 (the Brazilian resilient modulus method) uses 100 × 200 mm or 150 × 300 mm cylinders, depending on the grain size; the MR DNIT 181 fixture is supplied for 100 and 150 mm.

What is the difference between the basic and the automatic model?

The press is the same; the pressurization system changes. In the basic version, the pressure is pneumatic and set manually. In the automatic static version, the 1,600 kPa water pressurizer maintains the cell pressure and the back pressure and measures pore pressure and volume change; in the automatic dynamic version, the confining pressure is controlled automatically.

Can the dynamic triaxial testing machine measure the resilient modulus of asphalt mixtures?

Yes, with the diametral compression fixture, which has two horizontal LVDTs, according to DNIT 135/2018-ME (the Brazilian method for asphalt mixtures). For soil-cement, cement-treated graded crushed stone and other chemically stabilized materials, the press uses the MR DNIT 181 fixture, according to DNIT 181/2018-ME.

What computer does the triaxial testing software require?

Windows 10, with at least 2 GB of RAM (4 GB recommended) and a free USB port; the dynamic press also connects over a TCP-IP network. Installation is done by Biopdi technical support, by remote access or during on-site training.

Other soil testing equipment

See also our other soil testing equipment.

CBR / Marshall Test Press

Direct Shear Apparatus

Consolidation Test Apparatus

Request your quote

Price, terms and lead time for the triaxial press. Tell us your tests (UU, CU, CD, resilient modulus) and we'll recommend the model: static, dynamic or both.

Reply within 24 business hours

A proposal covering capacity, fixtures and the standards met, not just the price.

Configured for your test

Cell, devices and software selected based on your laboratory's test and standard.

In-house manufacturing, ISO 9001

Installation, training and technical support provided by the people who designed the machine.

Prefer to talk now

+55 (16) 3416-7080 +55 (16) 3413-6067 WhatsApp