Soil Strength (Triaxial)

The measurement of total stress or effective stress requires the use of different procedures and therefore different accessories and equipment.

Total stresses are normally measured in a triaxial cell where the sample is subjected to an all round confining pressure. A load is then applied through a piston onto a pressure pad. The sample is then confined in a rubber membrane and no drainage in to or out of the specimen is allowed. Pore water pressures are not normally measured and the quick undrained test is often referred to as the QU-TXL test. An extension of the QU test is the unconsolidated undrained test (UU), this is similar to the QU test but is run at a slower rate in order to measure pore water pressure.

Effective stresses when measured in a triaxial cell are more complex in their nature. Numerous parameters may be measured including back pressure, pore water pressure and volume change. From these values various engineering properties can be calculated.

Effective stress tests are usually referred to as consolidated drained (CD) or consolidated undrained (CU). Generally the CD test is applicable to sands, and either the CU or CD test is applicable to clays. There are many special test variations within these basic test groupings.

ELE supply a complete range of Triaxial testing equipment which includes:

• Load Frames
• Triaxial Cells & Accessories
• Pressure Systems
• Mechanical or Electronic Measurement devices for Load, Displacement, Pressure and Volume Change

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