Resonant Column Apparatus (Stokoe Type)

Product Code : GDSRCA

For many years the resonant column apparatus has been used in research and commercial laboratories to estimate values of the shear modulus, G, and damping ratio, D, for soil specimens across the small to medium strain range (< 1 %).

The variation in these parameters with increasing strain magnitude allows engineers to conduct dynamic response analyses, such as those using finite element and non-linear analytical methods, which enable performance assessment of natural and engineered structures subjected to dynamic and cyclic loadings.

Further Information:
Key features Benefits to the user
Current driven actuator using a transconductance power amplifier: The impedance of magnet / coil devices change with frequency. At higher frequencies, using a constant voltage amplifier the current would be seen to reduce. As the torque is directly proportional to current, the torque will also reduce and a non-linear torque input would affect results. This effect is removed in the GDSRCA by using a current driven power amplifier.
Designed to provide maximum rigidity: Providing minimum losses and a more consistent frequency response. With no rigid support to the top cap it is completely free vibrating.
Dedicated GDS RCA software is used for control and data acquisition of the RCA apparatus: Simple automated tests ensures consistent results
Low equipment damping: The software switches the hardware to provide an ‘open circuit’ through the coils during free vibration decay, which prevents ‘back’ EMF generation and reduces equipment damping effects.
Electro-magnetic drive system: Which incorporates precision wound coils and composite sintered neodymium iron boron (NdFeB) “rare-earth” magnets.
Internally mounted, counter-balanced accelerometer: Used to measure vibratory response of the sample.
Internal cell: To surround sample with water, to avoid air penetrating the membrane.
Operating Frequency (Hz)

0 to 300Hz

Pressure Range (MPa)

1, 2

Sample Sizes

38, 39.1, 50, 66, 70, 100mm

  • Lifting frame for easy cell top removal.
  • Vertical bender elements (S and P wave).
  • Torsional shear upgrade using non-contacting proximeter transducer.
  • From 1MPa (standard) to 2MPa.
  • Unsaturated testing (Method A).
  • Unsaturated RCA testing pedestals.