The GCTS Resonant Column & Torsional Shear Testing Systems combine the features of both resonant column and torsional shear devices into one elegant system. This enables them to evaluate the effects of a number of soil parameters, such as void ratio, confining pressure, strain amplitude, number of load cycles on shear modulus and material damping. By utilizing all available options, this system is capable of the full spectrum of modulus measurement, ranging from ultra-low strains to high strains with significant overlap.
For the resonant column test, a torsional drive is used to vibrate the top of the soil specimen at first-mode resonance at frequencies of up to 500 Hz while the bottom is fixed. A non-contacting rotational transducer is attached to the top platen monitor the torsional motion directly. The non-contacting sensor is located on extended arms to amplify the rotational deformation and provides a shear strain resolution of 10-6. An optional accelerometer can also be installed to measure large shear strains. These systems can also perform closed-loop torsional shear tests (stress or strain controlled) on the same soil specimen, either statically or dynamically, at up to 50 Hz.
With these systems, soil specimens can be tested under isotropic (hydrostatic) or anisotropic conditions. The driving and measuring system are mounted on a “floating” frame, which allows large vertical specimen deformations throughout the complete test. Its unique configuration also allows for very large shear deformations of up to ±20°.
ASTM D4015 Standard Test Methods for Modulus and Damping of Soils by Fixed-Base Resonant Column Devices
ASTM D7608 Standard Test Method for Torsional Ring Shear Test
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