Basic static triaxial testing system
Basic static triaxial press for UC, UU, CU and CD soil tests (ASTM D2166, D2850, D4767 and D7181): 50 kN electromechanical, 0.001 to 30 mm/min, manually set pressure.
The basic static triaxial press measures the shear strength parameters of soil, cohesion and internal friction angle. It has an electromechanical drive with a capacity of 5,000 kgf (49 kN), a ball screw actuator and position reading by a 0.001 mm encoder.
For the tests there are triaxial cells, load cells, LVDTs and the pressurization system, which in this model is set by the operator. The software handles setup, configuration, data acquisition, analysis and test reports.
The test procedures, with formulas and worked examples, are covered in the article on triaxial test. The four models are compared on the page for the triaxial testing system.
Types of tests
What each test measures, with which 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 |
Technical specifications
Data from the manual of the static triaxial testing machine (PTE-50k).
Basic 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) |
The drawing in the manual gives the machine dimensions: 1,563.40 mm overall height, 588.75 mm width and 400 mm between columns.
Main features
Electromechanical load frame (force application unit)
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
The machine, with the parts identified in the manual, and the front control panel:
Triaxial Cell
The triaxial cell with its parts named, from the machine manual, and the 3-inch cell mounted on the loading platen:
Pressurization System
In the basic model, the cell pressure is applied by a pneumatic system set manually by the operator, with a pressure regulator and valves. For back pressure and volume change measurement controlled by the equipment, see the automatic model.
Software: main functions
The Configuration tab of the software, with the machine connected and the load cell recognized:
Load cells
Fixtures
Pressurization system
Pressurization system for volume and pressure control of the triaxial cell.
Triaxial Cell
Triaxial cell built in acrylic and aluminum for triaxial testing of soils.
Load cells
Load cell for measuring the load applied to soil samples.
Frequently asked questions
The most common questions about the basic static triaxial testing system.
Which tests does the static triaxial testing machine perform?
Unconfined compression (UC, ASTM D2166) and the UU (ASTM D2850), CU (ASTM D4767) and CD (ASTM D7181) triaxial tests, conventional or saturated. The software checks the B parameter, records consolidation and plots the p, q or s, t stress paths and the Mohr circles.
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 in clay, which usually runs at hundredths of a millimeter per minute, calculated from the consolidation time of the test specimen.
How does the static triaxial testing system measure displacement?
The loading platen position is read by an optical encoder with 0.001 mm resolution, and the shortening of the test specimen by the 50 mm LVDT, with 0.01 mm resolution. The machine accepts up to four strain channels for LVDTs or extensometers.
What specimen size and pressure does the triaxial cell handle?
The cells take 38 and 76 mm diameter test specimens, with pedestal, top cap, porous stones and latex membranes for each diameter. They work at 1.0, 1.6 or 3.4 MPa, depending on the model; the Biopdi water pressure controller applies up to 1,600 kPa.
What computer does the static triaxial testing software require?
Windows 10, with at least 2 GB of RAM (4 GB recommended) and a free USB port. Installation is done by Biopdi technical support, by remote access or during on-site training.
What is the difference between the static basic and the static automatic triaxial testing system?
The press is the same: 50 kN and 0.001 to 30 mm/min. In the basic model, the cell pressure is pneumatic and set manually. In the automatic model, the 1,600 kPa water pressurizer maintains the cell pressure and back pressure and measures pore pressure and volume change, which makes saturated CU and CD tests easier.
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