Permanent Strain, Dynamic triaxial strength
A cylindrical soil specimen is sealed in a watertight rubber membrane and confined in a triaxial chamber where it is subjected to a confining pressure. An axial load is applied to the top of the specimen by a load rod. Specimens are consolidated isotropically (equal axial and radial stress). Tubing connections to the top and bottom specimen platens permit flow of water during saturation, consolidation and measurement of pore-water pressure during cyclic loading. Following saturation and consolidation, the specimen is subjected to a sinusoidally varying axial load by means of the load rod connected to the specimen top platen. The cyclic load, specimen axial deformation and pore water pressure development with time are monitored. The test is conducted under undrained conditions to approximate essentially undrained field conditions during earthquake or other dynamic loading. The cyclic loading generally causes an increase in the pore-water pressure in the specimen, resulting in a decrease in the effective stress and an increase in the cyclic axial deformation of the specimen. Failure may be defined as when the peak excess pore water pressure equals the initial effective confining pressure, full or 100% pore pressure ratio (sometimes called initial liquefaction), or in terms of a limiting cyclic strain or permanent strain. This test method is generally applicable for testing cohesionless free draining soils of relatively high permeability. When testing well-graded materials, silts, or clays, it should be recognized that pore-water pressures monitored at the specimen ends do not in general represent pore-water pressure values throughout the specimen. However, this test method may be followed when testing most soil types if care is taken to ensure that problem soils receive special consideration when tested and when test results are evaluated.
1 or more
Cylindrical specimens with a minimum diameter of 51 mm (2.0 in) and a height to diameter ratio of between 2.0 to 2.5, with maximum particle size less than 1/6 the diameter of the specimen
Consolidated-undrained tests, cohesionless soils, laboratory test, liquefaction, triaxial tests, cyclic triaxial test, dynamic