Demands from Australia-based Advanced Geomechnics - now part of Fugro - has led to geotechnical laboratory equipment specialist VJ Tech’s development of a new dynamic simple shear system with confining pressure.
According to VJ Tech, the system can be used to undertake a variety of tests including saturation, isotropic and anisotropic consolidation, K0, static shearing (direct simple shear), cyclic shearing with both strain and stress controlled and can be upgraded to undertake static and dynamic triaxial tests.
The company believes that the new system could be used to deliver test result for a number of different construction environments such as offshore, seismic, dam, embankment and pile analysis, as well as low stress testing.
VJ Tech has said that the main advantage of the system is that it is supplied with a pneumatic pressure controller to apply cell pressure and hydraulic pressure controller to apply back pressure to the sample. This allows the sample to be saturated in an incremental or ramped method used in effective stress triaxial testing allowing the user to saturated a sample before testing.
The horizontal and vertical stresses (total and effective) are controlled and measured using the supplied pressure controllers in combination with vertical and horizontal actuators to control the load, which cannot be done with a standard system.
The system also comes with a pressure sensor to directly measure pore water pressure in the sample, so the degree of saturation can be determined using a B value check, allowing the user to prove the sample is saturated.
The company also said that skirted top and bottom caps allows a range of material types to be tested easily compared to ridged or pin systems. Other advantages are that the internal pressure is compensated by submersible load cells on both axis so no correction is needed on tests for cell pressure acting on the load cell. The equipment does not call for metal confining rings that can cause additional friction in the results or for use of reinforced membranes.