UNSATURATED TRIAXIAL TEST PACKAGE
Soils in many cases are unsaturated in their natural state because of locating above of ground water level. It means that the pores are filled not only with water (liquid) but also partly with air(gas). The volume change measurement for this type of specimens is more complicated than the saturated specimens because of air inside of the specimen and the behaviour of air characteristics like as compressibility.
The Existence of air and water inside the unsaturated specimen generates the soil suction (when the pore-water pressure is less than the ambient air pressure). Soil suction influences the mechanical behaviour of unsaturated soils, including the shear and the compression properties. Accordingly, mechanical behaviour of unsaturated soils under triaxial stress-states shall be assessed under controlled-suction condition.
METHODS OF MEASUREMENT OF THE TOTAL VOLUME CHANGE:
- > On-sample strain measurement
- > Double Wall Cell
- > Direct measurement of the pore-water and pore-air volume change with Volume Pressure controllers (VPC)
- > Differential pressure transducer (DPT) measure the water head in an additional internal cell.
- Features
- Specifications
- Software
- Standards
- Applications
There are different techniques for unsaturated testing which the most popular ones for lab are:
- > Axis translation technique (ATT)
- > Vapor equilibrium method
- > Osmotic method
The axis translation technique is the most commonly used method in triaxial testing. It involves imposing and controlling positive air and water pressure in the soil sample (higher than atmosphere pressure) and allows controlling the matric suction in the soil. This technique is particularly useful for testing specimens with suction values greater than 100 kPa avoiding problems associated with cavitation.
In this Method for triaxial tests, a high air entry value (HAEV) ceramic disc which allows passage of water and not air below a given air pressure is placed bottom of the specimen and the normal porous stone is placed at top. Air and water pressure are independently applied and controlled in the sample the pore air pressure is applied to the top of sample via a normal porous stone while the pore water pressure is applied to the bottom of sample via a HAEV porous disc.
The main required components to run an unsaturated test are:
- High Air Entry Porous Disc
- Air Pressure Controller to apply pore air pressure (APC)
- Unsaturated Software Module for GEOsys
- Measuring set up for total volume change measurement
- Detailed information will follow soon
The unsaturated module is an add on module for GEOsys software and enable the user to configure and control of all components of testing e.g. axial stress, axial strain, pore air pressure, pore water pressure, cell pressure and etc.
One unique platform address all of your testing needs in geomechanics testing. There are various test modules, which combine with GEOsys and cover all your test requirements.
- Not available
- Detailed information will follow soon